Cumulus Support

I have just acquired a new MetPlus datalogger from Instromet (19200 baud rate) and I am trying to use Cumulus 1 (version 1101). The software appears to communicate with the sensor, but some of the readings are going haywire - sunshine increments too quickly, rainfall increments, and wind speed spikes. In fact, the stronger the wind, the worse the errors get.

I've attached the files as requested by email for you to take a look and see what is happening.

Mike Lewis

It appears to be a problem with your station. If you look in the debug log, you can see the responses from the station to requests for live data - they're the lines starting 'rdlv'. the format of the response is:

rdlv,temp1,temp2,hum,pressure,windspeed,winddir,sunhours,rain,checksum

The sunhours and rain figures are 'rolling' counters, i.e. they just keep incrementing.

Here's the response at 10:01:52

3668.332 : 10:01:52 57:RDLV
rdlv,14.3,14.9,,985.9,2.5,313,60.98,120.04,198

sunhours=60.98, rain=120.04

And 20 seconds later:

3687.832 : 10:02:12 57:RDLV
rdlv,14.3,14.8,,985.9,0.9,306,61.60,120.77,195

sunhours=61.60, rain=120.77

So the stations says that in those 20 seconds, your sun hours increased by 0.62 hours, or just over 37 minutes.
In the same 20 seconds, your rain counter increased by 0.73 mm, which is quite high for a 20 second period, unless it's raining heavily.

Do you think the problem is one of communication between the datalogger and the PC? The datalogger appears to function normally until connected to the computer. The logger did not come with a RS232 cable so I reused a much older one. Originally, the cable didn't work at all, but only when the red and black wires were crossed did the logger come to life (but maybe not correctly)?

Mike

northantsweather wrote:Do you think the problem is one of communication between the datalogger and the PC?

No, because the responses have a checksum, so if they were corrupted, the checksum validation would fail. Whether plugging in the cable in could cause the problem is another matter, but I'm not a hardware expert.