FAQ

The Cumulus FAQ (consult also the Help screens within Cumulus software)

If you think a question is missing from the FAQ, please add it - together with the answer!

Installing and Running Cumulus

What operating systems does Cumulus run on?

Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows Home Server, and Windows Server 2008. It may also work on Windows 2000, but this is not supported. You will probably not be able to get it to work on Windows 2000 with a Fine Offset station.

It appears that Cumulus also runs on Windows 8. You may have minor issues with minimising to the task bar and similar functions.

What do I need to get right when first getting Cumulus?

The installation process for Cumulus displays readme.txt, that has many tips. See also Setup. Below are three key points.

1. Install Cumulus in its own directory directly under a drive root.
2. Connect your weather station before you start Cumulus
3. When you first run Cumulus, it displays the Station settings screen. On this, make sure you pick the right sort of station (to ensure Cumulus communicates correctly with your weather station, and can identify all the observations) and choose your units wisely. (Changing units later means all stored numbers up to that point have to be converted manually). See the Help for information about the rest of the screen, but generally you can easily adjust the other options later.

What weather stations does Cumulus work with?

• Davis Vantage Pro (VP), Vantage Pro2 (VP2), and Vue.
• Oregon Scientific WM918, WMR918, WMR928, WMR968, WMR88 (see this FAQ), WMR100, WMR180, WMR200.
• Fine Offset - stations which use the Easyweather software such as MyDEL, Nevada, Watson and Fine Offset, with model numbers such as WH1080, WH1081, W8681, 265NC etc.
• La Crosse WS2300 range (see this FAQ). You may have problems with corrupt data if you use a WS23xx with a serial/USB adapter; this combination is therefore not supported.

For a more complete list see the Supported Devices page.

Will you support a new weather station type?

It’s quite hard to support a particular weather station when I don’t have access to one. No weather station is perfect, and problems inevitably arise after the code is written, and I have to start adding more and more code to work around issues with the station. Also, most companies don’t seem to like third parties writing software for their stations, so don’t make the protocol available. I will only consider adding support for a station under a certain set of circumstances which would include at least:

• A significant donation towards Cumulus development
• A well documented official protocol spec
• Loan or donation of a station
• Access to technical support from the station manufacturer

Please contact me if you would like to discuss this further

How do I request a new feature for Cumulus?

Please create an enhancement request.

Why haven't you added the feature I asked for a long time ago?

I develop and support Cumulus in my spare time, and I have a full time job. I invite donations, but I don't make a living from Cumulus. I add facilities when I can. There is a long list of enhancement requests already, and I am slowly working my way through them as time permits. If there is an enhancement request for the facility you have asked for, and the facility is a reasonable one (in my opinion) then I will hopefully get around to adding it one day. Please be patient.

How do I upgrade to a new release?

Just run the installer for the new version. Your data and settings are not affected, but of course you should back up your data and any settings files (e.g. cumulus.ini and strings.ini) before you run the installer. You can install the new version to the same place as the previous version, and the installer will offer this as the default. Occasionally, there may be actions you need to perform before or after the upgrade - these will be documented in the readme.txt file, which will appear when you run the installer, and also usually in the announcement of the version you are installing.

During the install, you will be given the option of re-installing the Cumulus HTML template files. If you have customised the existing pages, you might want to untick this option so that your versions don't get overwritten. Alternatively store your customised pages in a directory outside the Cumulus folder, and specify up to 10 such files on the local side of the files tab in the Configuration menu Internet settings screen and untick Include Standard Files. (100 such files can be specified in Cumulus.ini).

Cumulus will always install the HTML template files to a folder called 'originals' in the 'web' folder, so you can look at them to see if there are any changes you might want to include in your customised versions.

These instructions apply whether you are upgrading to/from a beta version or a 'release' version.

How do I back up my data, or transfer it to Cumulus on another computer?

Copy the contents of the Cumulus ‘data’ folder. If moving to another computer, you may also want to consider copying your cumulus.ini file, so you keep your settings - you may need to 'tweak' a few things (serial port number etc). If you have any files that you have created or modified yourself - a strings.ini file and/or a twitter.txt file, for example, you may want to copy those over too, along with any customised web pages. This article in the wiki gives more details above moving Cumulus: Moving cumulus

What are the formats of the Cumulus data files?

These are detailed in the Log Files section of this Wiki and also in the Cumulus help file, in the section “Data log file format”

I was away on the last day of last month - How do I see the final 'this month' figures for last month?

From version 1.9.3, Cumulus creates a daily backup of the log files. Look in the backup\daily subfolder within your cumulus installation.

These daily backups will be created if cumulus was left running during the period of interest, or stopped before that period and since restarted.

Open as a text file month.ini in the folder whose name is bearing the timestamp after your final rollover.

Note - in a similar manner if you miss the last day of the year, see the final 'this year' figures for last year by opening year.ini from the appropriate backup.

What do the various wind speeds in Cumulus correspond to, with Davis stations?

Davis stations supply two windspeeds, a 3-second average and a 10-minute average (later versions of the firmware also supply a 2-minute average, Cumulus currently doesn't use this).

• The Davis 3-second average is treated by Cumulus as 'Latest' (available via <#wlatest>)
• The Davis 10-minute average is the Cumulus 'Average' (available via <#wspeed>).

Note that if you sample these readings at shorter (real time) intervals it is possible for Cumulus 'Latest' to be lower than Cumulus 'Average' because approximately half of the 3-second wind speeds will be higher and half of them lower than the 10-minute average.

Davis stations do not supply the 'Gust value. The Cumulus 'Gust (available via <#wgust>) is a value calculated by Cumulus by capturing the highest of the station's 3-second readings over the previous 10 minutes.

What do the various wind speeds in Cumulus correspond to, with Fine Offset stations?

Fine Offset stations measure wind over 48-second intervals, divided into 24 2-second intervals. At the end of each 48-second period, they report the highest of those 24 values as 'Gust', and the average of those 24 values as 'Wind'. Cumulus, for various reasons, uses different terminology, and also has configuration settings which control how some of the wind values are displayed.

• The Fine Offset console 'Gust' value becomes Cumulus 'Latest'.
• The highest of Fine Offset 'Gust' values over the previous 10 minutes becomes Cumulus 'Gust'.

Cumulus 'Average' can be calculated in 3 different ways:

• The Fine Offset console 'Wind' value becomes, with default settings, Cumulus 'Average'.
• All Fine Offset 'Gust' values read over a 10 minute interval are averaged to become Cumulus 'Average' if in the Settings frame of the Station screen in the Configuration menu, you select Calculate 10-min wind average.
• All Fine Offset 'Wind' values read over a 10 minute interval are averaged to become Cumulus 'Average' if in the Settings frame of the Station screen in the Configuration menu, you select Calculate 10-min wind average and also set the next option Use 'speed' for avg calculation.

Note if Cumulus is being re-started, the Fine Offset 'Gust' and 'Wind' values will initially only be available at the station's logging interval, so the last two options may only be averaging a couple of readings.

How do I set up recording wind speeds in Cumulus, with Oregon Scientific and La Crosse stations

La Crosse and some Oregon Scientific weather stations only output a single wind speed. To allow Cumulus to calculate 'gust' and 'wind speed' with different values, select the Station dialogue from the Configuration menu and set Calculate 10 min wind average in the 'Settings' frame, so in cumulus.ini this will produce the parameter 'Wind10MinAverage=1 when cumulus is next stopped.

• The station's 'Wind' value will then display as Cumulus 'Latest'.
• A 10 minute average of the station's 'Wind' value will then display as Cumulus 'Average'.
• The highest of the station's 'Wind' value in a 10 minute period will then display as Cumulus 'Gust'.

How do I make Cumulus run automatically when Windows starts?

There is no option in Cumulus to set this up automatically as I prefer to leave it under the control of the user: The safest and most reliable method is simply to put a shortcut in your Startup folder. If you are running Vista or Windows 7, you may find that Cumulus gets blocked by UAC if you try to run it from the Startup folder, in which case it is recommended that you use Task Scheduler instead. See here for a good description of how to do this - http://blogs.techrepublic.com.com/window-on-windows/?p=616

Why are the 'Yesterday' figures missing on the Main Cumulus Screen?

The yesterday values on the Main Screen under "Recent Extremes" are not shown when the end of day rollover has not taken place. The usual cause of this is allowing your PC to 'sleep' while Cumulus is running. The support forum mentions a few other causes.

How does Cumulus handle Daylight Saving Time?

As far as the timestamps in the logs (and the graphs) are concerned, Cumulus doesn't do anything in particular for DST. It generates timestamps based on the Windows clock. So basically, at the start of DST (i.e. when the clocks 'go forward') you will get an apparent gap of one hour in your data, and similarly at the end of DST (i.e. when the clocks 'go back') you will get an apparent hour of duplicate timestamps in your logs and graphs. The exact timing of the affected hours depends on the type of station and when Cumulus was running. You will tend to get better results if you leave Cumulus running during the clock change.

What formula does Cumulus use for Apparent Temperature?

It uses a formula from the Australian BOM - http://www.bom.gov.au/info/thermal_stress/#atapproximation

Note that the version used is the one that doesn't take into account solar radiation.

How does Cumulus know the height of the cloud base?

It doesn't. It uses a calculation which gives the theoretical height above ground level at which Cumulus clouds might form, based on the current temperature and dew point. It assumes that the difference between temperature and dew point decreases by about 4.4 degrees Fahrenheit per 1000 feet increase in altitude. When the two values coincide, the air is saturated (relative humidity = 100%) and Cumulus clouds may form.

How is my rain rate calculated?

For stations which supply a rain rate, Cumulus uses that. For stations which don't supply a rain rate (e.g. Fine Offset and La Crosse), Cumulus simply takes the rain total from the last five minutes and calculates a rate based on that; e.g. a single tip of 0.3mm in 5 minutes is a rate of 3.6mm/hr. When data from the station's logger is used, a similar calculation is performed, but the interval used is the logger interval rather than five minutes.

Where does Cumulus get its monthly and annual rainfall totals from?

It adds up the corresponding daily totals in dayfile.txt, and then adds today's total so far to it. If your monthly and/or annual totals are incorrect, then you need to correct the daily totals which make up those figures, with Cumulus stopped. You can also use the built-in dayfile.txt editor to amend the daily totals; you will then need to restart Cumulus to get the monthly and annual totals recalculated.

If your all-time (or month by month from version 1.9.3) high monthly rainfall record has been affected, once you have corrected the figures in dayfile.txt and your monthly total is correct, you can then use the built-in all-time (or monthly records) editor(s) in Cumulus to regenerate the extreme records from dayfile.txt.

How do I reset all my data to start again from scratch?

Stop Cumulus and delete all of the files in the data folder. You may also want to edit the 'StartDate=' line in cumulus.ini to set the date for the start of your data.

How do I localise Cumulus to my own language?

Cumulus does not directly support languages other than English. It was never intended for use in other languages, and it is not possible to add support for this now. However, the text used for:

• Forecasting
• Moonphases
• Beaufort Scale
• Trend descriptions
• Compass points
• Graph titles
• Extra sensor channels

can all be customised by using the strings.ini file. This facility may be extended to allow other items to be translated, but it is very unlikely that there will ever be a fully multi-language version of Cumulus in its current form.

Also see this wiki page: Other Languages for information about customising the web pages.

Can I connect/disconnect my weather station while Cumulus is running?

No. You must make sure your weather station is connected to your PC and switched on, before running Cumulus. Do not disconnect your station while Cumulus is running.

How does Cumulus deal with extra sensors?

Cumulus has the ability to input, log, and display Current Values/Outputs from the Hydreon Optical Rain Sensor - Model RG-11 and from either Oregon Scientific or Davis extra sensors. Only today's and yesterday's total rainfall from a Hydreon sensor are available in today.ini and yesterday.ini. For some Oregon Scientific models, the temperature from an extra sensor can replace the temperature from the main sensor for processing by Cumulus, but all extra sensor values are stored in a series of monthly log files. No other processing is performed for Davis extra sensors, but past values are retained in a series of monthly log files. The file strings.ini is used to customise the description associated with extra sensors.

What is this "Solar Max" value which Cumulus is displaying?

It's the current theoretical maximum solar radiation value at the current date and time at your location. It is calculated using the Ryan-Stolzenbach formula, and uses the 'transmission factor' configurable in the station settings to allow for the effect of transmission through the atmosphere. The figure is not particularly useful in itself; it is used if you have a solar sensor, to compare with the current solar radiation reading, in an attempt to determine whether the sun is currently shining or not.

My Fine Offset console says the memory is nearly full - how do I clear it?

You don't need to, and it's much safer if you don't; clearing the memory could lead to a loss of data. The memory indicator on the console has no effect on the logging of data; the console will automatically start re-using the oldest memory locations.

How do I get my Davis station with USB working with Cumulus?

Cumulus cannot drive the station in USB mode, you must install 'virtual serial port' drivers, and configure Cumulus to use the virtual serial port. Make sure you have the station connected to the PC during the following operations.

You should first make sure that you can use the station with Weatherlink, in serial mode. If you have not already installed the Weatherlink software, install the version which came with your weather station. You should then upgrade to the latest version of Weatherlink; you can download the update from the Davis web site, here.

You now need to install the 'CP210X USB to Serial Converter'. You may find a link on your Start menu under 'Weatherlink'. Alternatively, you should find it in the folder where Weatherlink was installed, under 'Support' then 'Utilities'. Davis also make it available on their web site, here

It's a good idea to then update the driver to the latest version from the Silicon Labs web site, particularly if you use Windows 7. You can download it here - click on 'VCP driver kit' under 'Download for Windows XP/Server 2003/Vista/7' to begin the download. Run the executable once it's downloaded.

At this point, it's best to restart your computer.

You should now run Weatherlink, and attempt to connect to the weather station in serial mode. Weatherlink should find the appropriate COM port number automatically. If not, you can find it under 'Ports (COM & LPT)' in the Windows device manager. Look for the port called 'USB Serial Port (COMn)', where 'n' is a number. That's the number of the port you need to use in Weatherlink. If you cannot get Weatherlink to work using this virtual COM port, it is unlikely that you will be able to get Cumulus to work either, so either contact Davis support, explaining that you are trying to use the virtual serial port drivers because you want to run third-party software, or ask in the Cumulus forum, someone may be able to advise.

Once you have Weatherlink connected and working via the virtual serial port, close it down, and start Cumulus.

In the station settings in Cumulus, select the appropriate station type for your station; under 'VP Type' select Serial; in the serial port section enter the COM port number that you found earlier. You may need to restart Cumulus at this point. It will then start displaying live data. Note that the it deliberately does not download any historical logger data from before the current point in time. When you run it subsequently, it will download logger data to catch up if necessary from when you last ran it, but never from earlier than when you first ran it.

If you still having difficulty, the Davis Weatherlink manual offers this advice, which may be useful:

"Included with the WeatherLink software is a utility that allows you to convert a USB data logger from a direct USB data logger back to a USB data logger that emulates the serial port. To use this utility, select Convert USB to Virtual Serial in your WeatherLink program group on the Start menu of your computer (Start>AllPrograms>WeatherLink>Convert USB to Virtual Serial) and run the utility to convert your data logger. Please contact Davis Technical Support (“Contacting Davis Technical Support” on page 26) for more information."

Why does Cumulus do some things the way it does, when there are better ways?

Cumulus was originally something I 'knocked together' quickly when I got my first weather station, simply because I couldn't find any other software anywhere which I was prepared to use. No 'design' went into it, it was really just a prototype. Some of the things I did were just quick 'hacks' that I intended to fix when I did it 'properly'. But I never got around to going back and doing it 'properly', and it was never my intention that anyone else would use it. But I was persuaded to make it available for others, and then to add more and more enhancements. The fact that it works with several different types of weather station means that a lot of it is a compromise; it doesn't use certain features of the weather station which it could use if it were dedicated to that type of weather station.

So yes, I am aware that some of things that Cumulus does may seem strange, but it is simply not possible for me to start again from scratch, knowing what I know now. If you don't like the way Cumulus does certain things, do what I did and write your own software!

Troubleshooting

My 'Error' light is flashing

Click on it, and a window will open describing the error. It may just be a temporary ftp problem. If you want to stop ftp errors being reported in this way, you can turn them off in the display settings ("Show FTP errors on error log window").

I’ve configured my ftp details but the web pages aren’t appearing on my site

Try setting ‘use active FTP mode’.

I’ve tried active FTP mode, buy my web pages (or my realtime.txt file) still don’t appear?

Are you absolutely sure you have set the ftp path correctly? Most problems like this are a result of an incorrect path. Try turning on the ftp logging and look in the ftplog.txt and realtimeftplog.txt files. It is best to supply a relative path - i.e. with no leading 'slash'. Please don't ask me what path you need to supply, it is impossible for me to guess how your web space is set up. If you cannot work it out, ask your web space provider for help.

My ‘new record’ light has stopped flashing

It is the normal situation that the light does not flash. The ‘new record’ light only flashes when an all-time record has been broken. It stops flashing if you click on it or restart Cumulus, until another all-time record is broken. When you first start using Cumulus, inevitably the light will flash a lot, even if you cancel it, as you will be breaking records constantly. After a while, it will 'settle down' and not flash so often.

I installed a new version and my web page templates got over-written

The supplied web page templates are part of Cumulus and will be over-written on upgrade. If you want to create your own web pages, don’t edit the supplied ones, place them in a different folder and use the ‘extra files’ facility. From version 1.8.9, the installer offers the option of not over-writing the web templates; it unconditionally also installs them to a sub-folder of the web folder called 'originals', so you can refer to them if required, even if you chose not to over-write those in the web folder.

I can’t find my data files!

You’re probably running Windows Vista/Windows 7/Windows 8 (or one of the corresponding server versions of Windows). Look in C:\Users\[username]\AppData\Local\VirtualStore\Program Files\Cumulus - note that this is a 'hidden' folder. Ideally, to avoid this situation, you would install to somewhere outside the Program Files hierarchy, as recommended in the readme.txt.

I can't save my NOAA reports!

You've probably corrupted your Cumulus.ini file in the default Cumulus folder. See Cumulus.ini#Section:_NOAA. It can only be edited either (if Cumulus is stopped) with an external text file editor or (with Cumulus running) using the NOAA Setup in the configuation menu. Pay attention to where the quotes are required for the file names, and check that you have an allowed date format (see Webtags#Time.2FDate_.27format.27_Parameter).

My sunrise and sunset times are wrong

You've almost certainly entered your co-ordinates incorrectly, or not entered them at all - on the station settings screen. Make sure to use unsigned numbers for degrees, minutes, and seconds, with a 'W' for your longitude if you're West of the Greenwich meridian and the appropriate letter for your latitude.

One other less likely possibility is that you have set the wrong time zone on your PC. The times are updated when Cumulus starts, and once an hour (on the hour), so take that into consideration after you've corrected your co-ordinates.

The Moon rise or set time is showing dashes.

The moon doesn’t rise and set every day, the dashes appear when that event doesn’t occur on that particular day. The period between a moon rise and set is approximately 12 hours and 25 minutes, on average. The moon rises (or sets) approximately 50 minutes later, on average, each day. It therefore follows that sometimes the moon will not rise or set on a particular day - i.e. it had risen the previous day, or will set on the following day.

I’ve ‘zoomed’ a graph, how do I get it back to full size?

Drag from lower right to upper left.

My monthly and/or annual rainfall totals are wrong

The monthly and annual rainfall totals are calculated from today's rain total in today.ini and the daily totals in Dayfile.txt. There is a built in editor for Today's rain. The format of the dayfile.txt file is in the help file (in the section “Data log file format”), or in Wiki here; if you need to edit it:

• Optionally stop Cumulus and use an external editor to edit the daily totals in dayfile.txt until your monthly and annual totals are correct.
• Alternatively, you can leave Cumulus running and use the built-in dayfile.txt editor to amend the daily totals.

If you need to, you can specify a year-to-date total to add in for the period up to the point where you started using Cumulus, so that your first year’s total is correct. This is on the Station Configuration screen. Make sure you specify the first Cumulus operating year here, otherwise the extra will be added to the annual total for the wrong year!

In all cases then restart Cumulus to get the monthly and annual totals recalculated from correct daily totals.

If you need to correct within day values for trend graphs as well as the longer period totals, provided you know roughly when the rogue rainfall was recorded, find (and edit) it in the monthly_log_files, field 11 is the count used to derive other parameters.

The ‘gust’ line has disappeared from my graph

You probably have Cumulus set to calculate a 10-minute average, and your logger period is 10 minutes or longer, so your gust comes out the same as the average when using data from the logger.

My ‘gust’ values are the same as my ‘average’ wind speed values.

As above, you probably have Cumulus set to calculate a 10-minute average, and your logger period is 10 minutes or longer, so your gust comes out the same as the average when using data from the logger.

I’ve just installed Cumulus, and it didn’t download all the old data from my weather station

Cumulus deliberately doesn’t attempt to download any data from before the point when you first run it. If you wish, although this isn't recommended, you can force it to download data from any point by editing the ‘Timestamp’ line in the today.ini file (in the data folder), before starting it (you will need to have run it at least once previously).

If you do this, you will probably need to edit your log files in the data folder as you may have duplicate entries and/or entries out of order. Your rain totals will almost certainly also be wrong - the total for "today" in particular. See the FAQ entry about correcting rainfall data.

Note that this method does not work for the Oregon WMR200 station. This station deletes logger entries when they are downloaded, and there is no mechanism for retrieving logger entries for a particular period - it just sends all the entries that it has. You may be able to circumvent this by creating a today.ini file in the data folder before you run Cumulus, with just this in it:

[General]

Date=10/04/2012

Timestamp=10/04/2012 10:00:00

Change the dates and time to match the point from which you want Cumulus to start downloading data. If the station has already sent the data, this may not work, unfortunately.

If you stored data from your weather station (on another file-based system) before you first ran Cumulus, then you may be able to (using a text editor outside Cumulus) generate Monthly log files for the pre-Cumulus period. See that Wiki article for more information on what you can then do with those files within Cumulus.

I have inserted pre-Cumulus data making 'Records began on' date wrong

Stop Cumulus and edit cumulus.ini (station section) within the main Cumulus folder. Change the "StartDate=" line. Be sure to use the same format for the date.

This start date (that Cumulus first started tracking all-time records) is on the default Cumulus recordsT.htm template twice once with the label "Records began on" followed by <#recordsbegandate>. Here are the extremes recorded since then. and once with the label "Records since" followed by <#recordsbegandate>, note it does not need to be updated for Cumulus to recognise earlier data in log files in its data subfolder and obviously there is an alternative of editing description to say "Cumulus began on" and leaving cumulus.ini unchanged.

Cumulus doesn’t show the same pressure as my Fine Offset console

Cumulus displays pressure corrected to sea level. The console calls this ‘relative pressure’; it displays the letters "rel" when this is being displayed. The Fine Offset stations only supply absolute/station pressure to Cumulus, so Cumulus applies the adjustment to sea level. It does not use the altitude setting in the cumulus station configuration screen.

Normally when Cumulus starts, it reads the pressure ‘offset’ (the difference between absolute/station and relative/sea level pressure) from the station; it uses this subsequently to calculate the sea level pressure (each time when reading the absolute pressure sent from the station), but it is possible to define the offset in cumulus.ini instead.

First of all, check that you are comparing the Cumulus display with the ‘relative’ pressure on your console, and that you do not have a 'EWpressureoffset=x.y' line in the [Station] section of cumulus.ini. Make sure that you have set your console's relative pressure correctly - see your station manual for how to do this, typically tap the reading three times, then click '+' or '-'. The support forum includes discussion on where to find isobar charts or other sources to determine what the pressure should be. Obviously after any adjustment you need to stop Cumulus, because it is when you restart it that Cumulus reads the new pressure offset.

Sometimes the offset that cumulus reads is clearly garbage, so Cumulus uses zero as a best effort. In this situation, Cumulus will display the same value as the 'absolute' pressure on the console (no "rel" is displayed on the console when it is displaying absolute pressure). Often, if you restart Cumulus, it will then be able to read the correct value. If the problem happens often, you can circumvent it by editing cumulus.ini (while Cumulus is stopped), and in the [Station] section add an entry:

EWpressureoffset=x.y

where x.y is your pressure offset. Cumulus will then use this instead of reading it from the station. Note that you must supply the offset in hPa (i.e. the millibar units that the station works with) and that this circumvention generally stops Cumulus from agreeing with the relative pressure displayed on the console.

My pressure suddenly dropped! Or suddenly increased!

If you have a Fine Offset station, and this happened when you (re)started Cumulus, it is quite likely a problem with reading the pressure 'offset' from the station. See: "Cumulus doesn’t show the same pressure as my Fine Offset console" above

I get an error when I try to view my all-time records. Also, they don’t appear on my web site

The date format on your system has probably changed. Look at the Startdate line in cumulus.ini and check whether this is in the correct format for your system. If not, stop Cumulus and correct the date format.

I get an error when I close Cumulus

Cumulus does sometimes report an error when you close it. This does not appear to cause any problems, you can just close the error message. I don't seem to be able to do anything about this, as the 'crash' is not in code that I have control over. You may be able to avoid this error by avoiding closing Cumulus while it is uploading to the internet. Please don't bother sending me a bug report about this.

My forecast says "Not available"

You can get Cumulus to create a simple forecast by selecting 'Cumulus Forecast' on the Stations Settings screen.

My forecast always says "Exceptional Weather, Stormy, much precipitation"

You probably have incorrect Pressure Extreme settings in the Forecast section on the Station Settings window. Make sure that the values you have supplied match the units you have selected for the extremes. Note that the units for the extremes are not related to the units you have chosen for pressure display in Cumulus. The option of supplying mb/hPa or inHg for the extremes is merely a convenience; you can supply either, but the values and the units must of course match.

My computer hibernated/suspended, and I lost data/my graphs 'flat-lined'

Cumulus can't cope with being suspended, it just carries on as normal after being woken. There is an option in the station settings to 'close on suspend', so Cumulus will close itself as a safety measure, if you forget to do it manually. Don't use the 'close on suspend' option and the 'confirm shutdown' option at the same time; this will cause problems.

But I strongly recommend that you don't have your computer set to go into any form of standby while Cumulus is running - it's continuously gathering real-time data, after all, so it's a rather strange thing to do.

My heat index/humidex/wind chill is the same as my temperature

Wind chill only applies when the wind speed is above 4.8 kph and the temperature is below 10C. (The temperature cutoff is an option in Cumulus, but should really always be set). Heat index only applies when the temperature is above 27C and the humidity is above 40%.

The rest of the time they are the same as the ambient temperature.

While Humidex does not have any 'cutoff' values, at low temperature and/or humidity it will give the same figure as ambient temperature.

My station invented some rain that didn't really occur, and I want to set it to zero (or some other figure)

You can correct today's total using the 'today's rain' editor on the edit menu. You may choose to also stop Cumulus and edit today.ini to change the LastTip=(look up previous value in a recently backed up today.ini) parameter. Remember that 'ConsecutiveDryDays' does not include today.

If the erroneous rainfall didn't occur today, you just need to edit the total for the relevant day in dayfile.txt, using the dayfile.txt editor on the edit menu. You may then need to restart Cumulus to get the correct monthly and annual totals.

If your all-time records, or month-by-month all-time records have been affected, you can use the built-in editors to fetch the correct values once you have corrected dayfile.txt.

If the erroneous rain occurred yesterday, you can also optionally edit yesterday's total (which is only held temporarily for display purposes) in today.ini, while Cumulus is stopped.

Note that other rain figures, such as 'rain last hour' and 'rain last 24 hours' depend on a sensible progression of the rain counter, so it's not easy to correct this; it's easier to wait until the erroneous figure is far enough in the past so as not to affect the calculation. If you really do want to try to correct it, you would need to stop Cumulus and edit the 'total rain counter' values in the log file so they are correct relative to the current value of the rain counter (i.e. the latest one logged).

It is better to try to avoid spurious rain being recorded in the first place. Cumulus attempts to ignore large increases in the rain total automatically, and is quite often successful. For 'hourly rain' and 'rain rate', you can set 'spike removal' settings on the calibration settings screen. These apply only to Fine Offset and La Crosse stations (which are known to occasionally produce faulty rain readings).

Cumulus is showing a different wind speed compared to my console

You're probably misunderstood Cumulus processing of wind speeds, looking at different parameters, or different averaging periods.

• If you have a Davis weather station see #What_do_the_various_wind_speeds_in_Cumulus_correspond_to.2C_with_Davis_stations.3F
• If you have a Fine Offset station, see #What_do_the_various_wind_speeds_in_Cumulus_correspond_to.2C_with_Fine_Offset_stations.3F
• For Oregon Scientific and La Crosse stations see #How_do_I_set_up_recording_wind_speeds_in_Cumulus.2C_with_Oregon_Scientific_and_La_Crosse_stations

Note that you can't compare the graphs drawn by Easyweather and Cumulus unless you are certain that they are plotting the same data. They can't both be running at the same time, so one would normally be plotting 'live' data at a given interval, and the other will be plotting data downloaded from the station's logger. The wind speed will hence not normally be the same for a particular time on the graph as it may well have changed at the point that it is saved to the logger. The only situation where it would be valid to compare the graphs would be if neither were running at the times you are comparing, and both subsequently downloaded the same data from the logger.

I get error -32710 with Cumulus and my USB Davis station

The USB support in the Davis DLL which Cumulus uses doesn't seem to work. You need to use the CP210X USB/serial software which Davis supply, and use the station in serial mode. If you have previously been using your station with Weatherlink in USB mode, you will need to change to serial mode in Weatherlink before you can use the station with Cumulus. You can do this using this utility from Davis.

When I start Cumulus, the graphs restart again each time and don't show the earlier data

You probably have an error in one or more data files. Look near the beginning of the latest file in the Diags folder for an error message which will tell you which file is in error and which line is causing the problem. It may simply be a blank line. Edit the file with Cumulus stopped. Note that you may need to repeat this process; only the first error is shown.

This problem can also occur if you change your system format settings (date format, decimal and list separators etc). Again, check the diags file for a message about a number not being a valid floating point value.

My Davis station shows a higher maximum wind speed than Cumulus

The Davis DLL which Cumulus uses to read data from the station can sometimes miss readings. You can try to minimise the effect of this by editing cumulus.ini (with Cumulus stopped) and add a line to the [Station] section, thus:

VP2SleepInterval=0

This sets the interval between reads to zero (the default is 500 ms).

Cumulus won't read the data from my station

If you have one of the Fine Offset clones, make sure you have configured your relative pressure correctly. If Cumulus finds an 'impossible' value, it will ignore all data from your station.

The peak values on my graphs are not the same as my extreme values

The graphs are snapshots of the data, taken once a minute while Cumulus is running; it is not feasible to plot every data point. If the extreme value did not coincide exactly with the point at which the data was added to the graph, then it will not appear on the graph. The graphs are not intended to show all of the highs and lows, they are there to give an idea of the trends. This also applies to 'Select-A-Graph', which takes its data from the data logs; the highs and lows do not necessarily appear in the periodic data logs.

This is most noticeable with wind gusts, the value of which can change rapidly, even over a period of a minute. The 'Plot latest gust' setting causes the 'Latest' figure (as shown on the main screen) to be plotted. What this figure represents exactly depends on your weather station type. This figure may vary rapidly, e.g. on Davis stations, it changes every 3 seconds or so. The graphs are plotted once a minute, and hence, with Davis stations, for example, there is approximately a one in 20 chance of any given 'latest' figure actually being plotted.

Cumulus also stores the peak value of the 'latest' figure from the last 10 minutes. It calls this the 'gust', as this is a reasonable representation of a true 'gust' figure. If you untick 'plot latest gust', it will plot this figure instead. As it contains the peak figure from the last 10 minutes, and the graph is plotted once a minute, plotting this value means that the high gust figure will always appear on the graph.

My extreme values do not appear in the 'monthly' data logs

The data logs are snapshots of the data, taken at the configured interval while Cumulus is running (or at the station's configured interval when data is read from the station's logger). Cumulus reads the station frequently, detecting each change in observations, and can update extremes at each of these reading times.

If the extreme value reading time did not immediately precede a time at which the data was logged, then it will not appear in the log. This is most noticeable with wind gusts, the value of which can change rapidly between log entries.

Cumulus takes a long time to download the data from my Davis station at start up

When Cumulus starts, it asks the station for all the data from the logger since the last time it was running. If the timestamp that it supplies does not exactly match the timestamp of an entry in the Davis logger, the station has a strange 'feature' where it decides to send the entire contents of the logger. This will take some time to download, during which the Davis console display may appear to freeze.

It is recommended that you set the logging interval in Cumulus to the same interval as the station, then Cumulus will be able to make sure it uses a timestamp that matches an entry in the logger. Note that this is mentioned in the readme.txt file which appears during the Cumulus installation, which you were asked to read at the time. If you didn't read it, it is strongly recommended that you do so now; it contains important information.

Today is the shortest/longest day, but Cumulus says that tomorrow will be a few seconds shorter/longer

The routines I use to calculate the length of the day aren't really suitable for this level of accuracy. I don't consider it an issue.

Cumulus got the forecast wrong!

Cumulus uses a forecast based on the Zambretti Forecaster (see Google). I didn't design the algorithm myself and to be honest I don't know how it works, so I can't answer any questions about it. Note that this is a 'forecast' for the following 12 hours or so; it is not a 'nowcast' (what the weather is doing now). Please regard the forecast as 'for entertainment purposes only'. Do not base any decisions on it, and bear in mind that it is a very simple calculation based on only a few basic parameters. Some people get reasonable results, others do not. You can try tweaking the pressure extreme settings (in the Forecast section in the station settings), but don't expect the forecast to be as good as that provided by the weather agencies which have invested millions in their forecasting systems.

I only see one set of points on the wind direction graph

This happens just after you restart Cumulus, if the data came from the weather station's logger (i.e. Cumulus hasn't been running for a while). Weather stations only supply a 'current' direction, and Cumulus calculates the average direction when running 'live'. So there is only one set of data available to be plotted, if it comes from the station logger.

My graphs appear to be plotted less frequently just after Cumulus starts up

When running live, Cumulus plots data at 1-minute intervals. When it starts up, it pre-fills the graphs with data from the log files, which generally (depending on how you have Cumulus and your station configured) will be at less frequent intervals.

I closed Cumulus, the 'please wait' form appeared, but Cumulus didn't close, even after several minutes

If you've closed Cumulus shortly after it has downloaded a lot of data from the logger, it can take a while for the logging thread to get everything written away to disk, and Cumulus won't close until this has completed. However, in some circumstances, there seems to be a situation where Cumulus will never close, so you will need to close it with task manager. If you think you know what conditions cause this to happen, please let me know.

Cumulus isn't logging data at the interval that I set

It logs data at the interval you have configured, while it is running. If there is data to read from the station logger at start up, each logger entry is logged to the Cumulus log files, so those entries will be at the logger interval that you have configured in your station.

Cumulus takes a very long time to shut down

You may have closed it very soon after starting it up, when it had a lot of data to download from the station logger, and you use Weather Underground. From version 1.9.1 there is a facility where it 'catches up' with data that hasn't been uploaded to Weather Underground while it hasn't been running. This takes a little while, and if you close it while it is doing it, it will take a long time for all of the updates to time out. You need to give it sufficient time to finish the upload. From version 1.9.2, there is a 'catch up' light which shows that the upload is taking place, and the 'catch up' is optional'; and it will abort much more quickly if you still close it while the catch up is taking place.

My temperature Min/Max/Avg graph is empty

The most likely explanation is that you have only recently started running Cumulus (in the last day or two). It adds new values to this graph at the end of each day; it wouldn't make sense to add a value part of the way through the day, and you need a few points to be plotted before the graph starts to take shape. You need to wait until you have been running Cumulus for a few days.

If you've been running Cumulus for more than a few days, but the graph is still empty, the most likely explanation is that it was unable to read your dayfile.txt file. Look at the latest file in the 'diags' folder (the files are plain text) for error messages mentioning dayfile.txt.

The longest dry/wet spell for this month/year includes days from last month/year

This is intentional. I decided that it didn't make sense to arbitrarily chop off a dry/wet spell at the start of the month/year, as then the figure is meaningless. So the figures are to be interpreted as "the longest dry/wet spell which includes this month/year". I note that other software takes the same approach.

Cumulus isn't performing periodic tasks, like data logging or web uploads

Cumulus assumes a certain level of weather station functionality. It checks that it has received data from a number of sensors (e.g. pressure and outside temperature) before it starts logging or uploading to the web. If your weather station is not fully functional, you will not be able to use Cumulus fully. From version 1.9.3 onwards, you can over-ride the start up check by adding a line to the [Station] section of Cumulus.ini, thus:

NoSensorCheck=1

I've changed my Twitter password, and now Cumulus won't update Twitter

You need to force Cumulus to re-authenticate with Twitter. Stop Cumulus and edit cumulus.ini. Find the [Twitter] section, and delete the lines which start

OauthToken=

OauthTokenSecret=

Start Cumulus and it should be able to update Twitter again.

When I start Cumulus, I get the error message "The station is not initialised"

For Fine Offset stations, when Cumulus starts up, it checks the first two bytes of the station's memory. They are supposed to contain the values Hex 55 and Hex AA to indicate that the station has initialised itself correctly. If they do not, then presumably the station has had some kind of internal problem, so Cumulus doesn't try to read any data from it. A reset of the station normally fixes this - remove the batteries and the USB cable; but note that you will almost certainly lose any stored data in the logger.

If you want to force Cumulus to ignore this check (not recommended), edit cumulus.ini and add a line to the [Station] section:

EWdisablecheckinit=1

You will most likely not have any success with this, as your station memory is probably corrupted anyway.

Note that for this setting to work, you need to be using version 1.9.3, build 1034 or later.

How do I correct my all-time (or monthly) records?

Use the editor in Cumulus - on the Edit menu. If you know the correct figures, you can enter them manually. To aid in this, you can look at the Alltimelog.txt file to find the previous values for the all-time records. Similar entries are logged to the diags files for the monthly highs and lows. You can also get the editor to scan the data logs to find the highs and lows from the files, click the Help button for details.

It's January 1st and my 'rain since midnight' and/or 'last 24 hours rain' are wrong/negative

You are probably using a Davis station. Cumulus needs an incrementing rain counter to calculate all of the rain figures, and the nearest to that on a Davis station is the annual total. When this resets at the end of the year, this causes some of the rain data to show odd values for a day. You will notice this particularly if you use an 0900 start of meteorological day, as the 'rain since midnight' figure is used for services such as Weather Underground. There's no easy solution to this, sorry.

Cumulus stops at the "Downloading data" screen

If you have a Fine Offset station, this is probably caused by the station's interface locking up. You should be able to get it going again by doing a reset - remove batteries and the USB cable. Recent Fine Offset models have a problem where they can lock up frequently, requiring a reset. From version 1.9.3 of Cumulus onwards, there is an option to synchronise the reading of data with the console writing the data, to avoid doing both at the same time, and this seems to avoid most lockups.

If you look in the status bar at the bottom of the Cumulus window, there may a message "Error: no response"; this would confirm that the station has locked up and needs resetting.

If none of this helps, post in the forum, attaching your zipped-up Cumulus diags folder.

Cumulus locks up when it starts and I have to use the task manager to kill it

If you have a Fine Offset station, this is most likely caused by the station's interface locking up. You should be able to get it going again by doing a reset - remove batteries and the USB cable. Recent Fine Offset models have a problem where they can lock up frequently, requiring a reset. From version 1.9.3 of Cumulus onwards, there is an option to synchronise the reading of data with the console writing the data, to avoid doing both at the same time, and this seems to avoid most lockups.

If you look in the status bar at the bottom of the Cumulus window, there may a message "Error: no response"; this would confirm that the station has locked up and needs resetting.

The problem where Cumulus locks up when the station doesn't respond is fixed in version 1.9.4.

If none of this helps, post in the forum, attaching your zipped-up Cumulus diags folder.

Website

How do I replace the 'bird' image on the website?

There are several ways to change the image of the 'bird' on the standard Cumulus web page. You will need an FTP tool

• The simplest way is to upload a new picture to the images folder of your website; the file should be called picture.jpg. Please ensure the images not too large and bear in mind it will appear on the bottom left of the page; the site data may cover some of the image. As a guide, the default image is 600 x 450 pixels.
• Secondly, you may upload an image using your own file name. Edit the weather.css file and look for the line background-image: url(images/picture.jpg); around line 9 and adjust as necessary. Upload the edited css file to the website
• if you wish to remove the image completely edit the weather.css file and remove the line background-image: url(images/picture.jpg); Upload the css file to to the website

NOTE: It is not recommended that you overwrite the image in your local folder (webfiles\images\picture.jpg) because that gets overwritten when you update to a new build of Cumulus. Ideally your image will be in its own local folder outside the Cumulus structure.

How do I change the "Welcome to." on the front page

The Welcome message is controlled within Cumulus. Click on the Station Configuration within Cumulus and Edit the Name field within the Location section. The Description field is also used on the front page of the site.

I don't have a solar sensor. How do I remove the solar data from the supplied web pages?

Locate the Cumulus 'web' folder on your PC and edit the following files (there are comments in the html to guide you):

indexT.htm

Remove the following code:

<tr class="td_temperature_data">
     <td>Solar Radiation</td>
     <td><#SolarRad>&nbsp;W/m&sup2;</td>
     <td>Evapotranspiration Today</td>
     <td><#ET>&nbsp;<#rainunit></td>
</tr>

todayT.htm and yesterdayT.htm

Remove the following code:

<tr class="td_temperature_data">
     <td>Hours&nbsp;of&nbsp;Sunshine</td>
     <td><#SunshineHours></td>
     <td>&nbsp;</td>
</tr>

Why does a standard gauges web page have text where it should show gauges?

If a standard Cumulus 'gauges.htm' web page displays like this then either

1) (Most Likely) The weather station owner has not loaded the required files/folders onto his/her server;

• The gauges graphics require the 'images' subfolder (see next answer), containing the script and many images to be pre-loaded in the 'dbimages' subfolder.
• All these should exist within the destination folder that holds the HTML files as instructed in the Cumulus Help ('setting up your website' page)
• Also explained in Simple Website setup on this Wiki.

or 2) JavaScript is not enabled (or not available) in the browser being used to view the page (if not enabled, this can be switched on in either 'Options', 'Preferences' or 'Settings' depending on browser). Note that Firefox version 23 has removed the ability to change this in Option preferences, so ignore this solution in that browser.

or 3) You are using a browser add-on such as 'NoScript' (over 2 million use this) which requires you to explicitly turn on JavaScript for each web site you visit within the 'NoScript' options. (This sort of add-on may be used to restrict advertising or tracking of your actions, or for security against unwanted processes being started by sites you visit).

Why are there no graphs on my standard trends web page?

Either 1) You have not created an images sub-folder (within your folder that holds web pages) as instructed in the Cumulus Help ('setting up your website' page) - also explained in Simple Website setup. In this case, the bird image will not be appearing in the bottom left corner of your web pages.

Or 2) You have switched off Include Standard Images on the file tab of the Internet dialogue of the configuration menu. In this case Cumulus believes you are working in a non-standard way, and does not automatically upload the graphs (nor moon image).

What is the size of the standard Cumulus update?

The default is that all of the standard pages and standard images are uploaded on each update at whatever standard update frequency you select.

In total for version 1.9.2, it's about half a megabyte - about 100kB for the pages (about half of that is the gauges.htm page with all the detailed wind plotting points, and half the other pages) and 400kB for the variable images (moon phase, some gauges images and trend graphs - the exact size of latter can vary if you change the period they cover).

This excludes the realtime.txt file. It also excludes any additional file transfers you may add (e.g. dayfile.txt or files required by external sites). Version 1.9.3 adds the monthly records page which contains 12 months worth of a lot of data (although usually very little changes between updates), and adds 25kB.

The 'real time wind data' gauges on the standard gauges page aren't working

These require a realtime.txt file to be uploaded by Cumulus. Tick the "Enable Realtime", "Enable Realtime FTP" and "Enable realtime.txt FTP" boxes on the internet settings screen. If the gauges still do not work, check that the realtime.txt file is being uploaded to the correct place. If it is not, it is likely that you have specified an incorrect 'ftp directory' in Cumulus. If your 'normal' pages are being uploaded correctly, but realtime.txt is not, then it is likely that you simply need to leave the ftp directory blank (but see the note below first).

A possible cause for this problem is that your web space provider does not allow .txt files to be accessed. For example, the free hosting provider 000webhost.com do not.

I'm using the supplied web pages, and get lower case in places where I want upper case

It's in the CSS. Edit weatherstyle.css and find lines like: "text-transform: lowercase;" and remove them.

My web pages have things like <#location> in them

You’ve edited your templates with something like Dreamweaver, and it’s changed the angle brackets on the Webtags to "&lt ;" and "&gt ;" - you need to change them back to < and >. These may look very similar when viewed in your browser, but you can only generate the correct ones by using the appropriate keys on your keyboard.

Alternatively, if the web templates are listed in cumulus.ini (and for the first 10 appear on the files tab of Internet dialogue of Configuation menu), the Process option must be ticked for the web pages generated by Cumulus to have values replacing the Webtags. Otherwise at each web update, Cumulus will generate web pages the same as the templates.

Running a web server on the same PC as Cumulus

If you do not have a web site, or run a web server locally (same PC, or on your local network), you can get Cumulus to generate/copy html or image files locally instead of using FTP to place them remotely. You'll need to list the (source) file including paths on the files tab of the internet settings, and specify a destination path and file name for the remote file in each case. Don't tick the FTP? box for standard cumulus pages (the exception is for a local web server and any non-standard web page that attempts to read using a script a local file such as dayfile.txt as this does need FTP to generate the server-based web page). For the standard images, you can supply a folder name (specify on the same screen), and they will all get copied there. Set everything else up as if you were using ftp, but don't supply a host name etc (except for exception already mentioned).

There's a limit of 10 files on the files tab, but you can increase this to 20 files in version 1.9.2 (in version 1.9.3 it is 100 files) by editing cumulus.ini, with Cumulus stopped. Follow the format of the entries for first 10 files.

Error Codes generated by FTP or Winsock

You should be able to look these up on the web. Try Here

How do I configure Cumulus for Secure FTP (SFTP/FTPS)?

Cumulus doesn't support Secure FTP. You can configure Cumulus to invoke an external program like WinSCP, as described here: SFTP article

Directory related problems in FTP

The following pointers should help:

• On the Internet settings screen in Sites/Options the optional Directory parameter required is the path from your FTP root, to where the web pages are to be stored. Click the Help button for full explanation, or search the support forum as many people have found this is the hardest parameter to get right.
• The standard pages are uploaded after a 'change directory'; if this fails, the files will still be uploaded to the FTP server root. So some mistakes do not matter because if no change of directory was actually required, your files will be uploaded correctly.
• If you have enabled Realtime, the realtime.txt file is uploaded without doing a change directory, by appending "/realtime.txt" to the supplied directory. In this case, if the web site directory is invalid, the upload fails.
• On the NOAA Setup screen the optional Directory parameter required is the path from your FTP root, to where the web pages are to be stored. Click the Help button for full explanation. Like realtime.txt, the upload is by appending the filename for the report to the directory and will fail if the web site directory is specified wrongly.
• See Setting up your website in Cumulus help for a simple guide to the subfolder structure you need to create and the list of files that need to be uploaded manually when first installing a website. Or see Website_setup for all the options.

Selecting a Weather Station sensor site

Note: Some stations have all sensors in one unit, positioning of these is a compromise between the ideals for each sensor. A good (portable document format) guide to all the conflicting siting standards is at Campbell Scientific.

For more advice see the website of your local Meteorological Bureau, an educational place (e.g. in USA see Cornell University), the World Meterological Organisation, or a specialist organisation (e.g. in UK see Royal Meteorological Society rather than the Met Office web site).

If you are contributing to an external site like APRS/CWOP, Weather Underground, PWS weather, Weatherbug and/or WOW, these destinations may offer site placement classifications.

Where should I position the wind sensors

If you are mounting on a building of height 'h' above ground level, ideally the wind sensor should be at a height of '1.5 times h' above ground level.

If you are positioning away from a building or tree (or other object) of height 'h' (or the mean height of several objects is 'h'), then the distance away depends on which standard you are trying to meet, and can vary between 1.5 and 3 times 'h'.

In the UK, the recommended height is 10 metres. Advice varies on whether you should apply a correction factor for any lower height. Cumulus allows you to apply such a factor to either just wind speed, or wind speed and gust speed, by using the Calibration screen within the configuation menu. In the Cumulus Help it recommends that you also adjust wind chill - in practice this means ask Cumulus to calculate wind chill by selecting this in the settings frame on the station settings screen accessed from configuration menu (ignore any wind chill output by your weather station).

Where should I position the rain sensor

See Rain measurement or your local offical organisation.

The WMO says the rain gauge should at a distance away of 2 times the height of each nearby object (buildings, trees, walls, solid fences etc.) and just high enough off ground level to avoid possibility of splashing. You can experiment, but for amateurs, no more than a metre off the ground (or roof if mounted above it) and at least a metre from any chimney, wall or solid fence whose height exceeds that of the sensor seems good enough for most gauges.

How do I protect my rain gauge against spiders or other natural problems

There is a lot of discussion on the Homebuilt forum.

How do I get good temperature and humidity measurements

The international standard states ambient air temperature/humidity is measured at 1.25 metres above ground level, above soil or grass not paving, protected from direct sun radiation (and direct rain), unless you are measuring soil or ground temperatures. Modern Stevenson Screens are uPVC constructed with a black interior (so they do not radiate heat onto the sensors) and a white exterior (so they reflect as much radiation as possible). An air frost is defined as a temperature below the freezing point for water at this height.

There is a lot of discussion on the Homebuilt forum about different approaches to improving measurements, and the problems with out of the box instrumentation from the different manufacturers.

(If you are using a Fine Offset sensor, the thin depth of the thermonmeter/hygrometer should face where your receiver is, for maximum transmission strength, so the wide face is at right angles to the transmission route).

Pressure

Varies with altitude and temperature, but no significant variation with spatial position with regard to nearby fixed bulky objects. Often measured indoors, only consideration will be trying to avoid any forced ventilation or extraction as such air moving systems could have different pressures on intake and outlet sides. Equally operation in close proximity to fast moving (road or railway) vehicles or tunnels can distort readings.

Solar

It is obvious really, solar sensors should be positioned for maximum unshaded exposure to sunlight throughout the year.