Absolute Pressure

[iandrews]

Hi,

Have a Maplin WH1081, been getting some data spikes and lost sensor messages recently, so have changed batteries in the outdoor unit. Once I had done this the indoor unit wasn't "updating" the outdoor data, so I popped the batteries out, of the consols and back in again. Once I had done this it started to receive the outdoor data again.

However I now have an issue with the console showing a absolute Pressure of about 1230, it was about 1010 before I pulled the batteries. I have tried leaving the batteries out of the console unit for about 5 mins, but still the same. I have set the relative pressure to what a nearby station is showing (1011), and started Cumulus, and all seems ok as the pressure is showing at 1011.

I assume sometime has gone "wrong" with the console, and have read a couple of things where others have a absolute pressure that is over 100 out. Do I need to do / check anything else. I think Cumulus reads the difference between the absolute and relative pressure at start-up (can I "see" this value anywhere), and then uses this, so as long as the absolute remains the same all should be ok.

Ian.

[steve]

I think Mark Crossley also has a 'way off' absolute pressure reading, and like you he has set the relative pressure correctly regardless of that, and his continues to display a good relative pressure.

You can see the 'offset' which Cumulus applies, as calculated from the pressure values read from the station, if you look in the diags files at around line 85 or so. For example:

7/27/2012 19:10:33.515 : EWUSB: Read pressure values: rel=1011.1 abs=997.8 offset =13.3

[iandrews]

Thanks Steve,

That line says:

29/07/2012 13:56:36.185 : EWUSB: Read pressure values: rel=1011.3 abs=1229.7 offset =-218.4

So as you can see, quite an offset. Not quite sure why it's suddenly done it. Odd thing is, when I put the batteries back in, despite the absolute being way off, the relative was only 2 or 3 out.

Maybe I will be lucky like Mark, and it will be fine, just need to remember / check if I need to change batteries again.

Otherwise Maplins have one of their offers on at the moment where they are selling it for £69, so maybe I can get a new one (and have some spares). Or I could use this as an excuse to "upgrade" to say a Davis unit.