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WH1080 Station Settings

Discussion specific to Fine Offset and similar rebadged weather stations
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Repairman77
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Re: WH1080 Station Settings

Postby Repairman77 » Thu Oct 29, 2009 10:04 am

Update...

Well after a couple of weeks trying to calibrate the WH1080 with external instruments I've come to the conclusion that you are unlikely to ever get it really accurate; even with the excellent configuration/calibration part of Cumulus.

It would appear that the 3 main sensors, temperature, pressure and humidity are all affected by the other functions; for example the pressure is affected by temperature and humidity, the temperature by humidity, and the humidity by outside temperature. Hence Pressure can be up to +/- 1mB, Temperature +/- 1 degree C, and humidity (difficult to measure at the best of times) by several %.

I suppose it would be possible with extra functions in the calibration section to link all results and compute all three more accurately, but it would be quite a job compiling all the data and applying all the corrections; as well as needing a lot of data in the first place to work with. Perhaps Cumulus2 could contain it but I'm not sure if it would be worth all the effort.

The rain gauge seems to be a bit of a hit and miss device, but I haven't had enough rain here to do too many tests. I think I'll be lucky if I get anywhere close to 10% accuracy though. Luckily I still have the normal rain gauge in use.

I guess it's not a bad set-up for the price but I guess I am expecting a little too much of it.

Has anyone else done tests with the WH1080 against more accurate equipment and obtained better calibration? I would be interested to know. I guess most users take all the readings as gospel, unless they have any equipment to check it against.

Mike.
Retired Radio and Electronics Engineer residing in Cambridgeshire, UK.

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steve
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Re: WH1080 Station Settings

Postby steve » Thu Oct 29, 2009 10:47 am

I did some comparisons against my VP2, and the results weren't bad, but it was in a very limited set of a conditions, and it wasn't a very scientific test. Worst performer seemed to be humidity, which is several percent below the VP2. The rain gauge invents rain during high winds - it's firmly attached to my stevenson screen, so the problem seems to be wind getting in and tipping the buckets.
Steve
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Repairman77
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Weather Station: WH1080
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Re: WH1080 Station Settings

Postby Repairman77 » Thu Oct 29, 2009 4:13 pm

steve wrote:I did some comparisons against my VP2, and the results weren't bad, but it was in a very limited set of a conditions, and it wasn't a very scientific test. Worst performer seemed to be humidity, which is several percent below the VP2. The rain gauge invents rain during high winds - it's firmly attached to my stevenson screen, so the problem seems to be wind getting in and tipping the buckets.

Thanks for you reply Steve.
I don't know the VP2; perhaps you could supply a link to the advert.
Humidity is a difficult thing to measure, even in a laboratory; the WH1080 humidity readings seem a bit erratic with quite a bit of hysteresis.
Mike.
Retired Radio and Electronics Engineer residing in Cambridgeshire, UK.

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steve
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Re: WH1080 Station Settings

Postby steve » Thu Oct 29, 2009 4:31 pm

The VP2 is the Davis Vantage Pro2; costs about 10x as much as a Fine Offset: http://weatherstations.co.uk/vp_main.htm
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Repairman77
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Weather Station: WH1080
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Re: WH1080 Station Settings

Postby Repairman77 » Thu Oct 29, 2009 4:41 pm

steve wrote:The VP2 is the Davis Vantage Pro2; costs about 10x as much as a Fine Offset: http://weatherstations.co.uk/vp_main.htm

Looks like a nice piece of kit Steve; unfortunately beyond my means.
Mike.
Retired Radio and Electronics Engineer residing in Cambridgeshire, UK.

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steve
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Re: WH1080 Station Settings

Postby steve » Thu Oct 29, 2009 5:15 pm

Repairman77 wrote: unfortunately beyond my means.


Beyond mine too. I paid about half the UK price, but unfortunately it's no longer available from that source.
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Keyz
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Weather Station: WH1088 (actually WH1081/3)
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Location: Auckland, NZ

Re: WH1080 Station Settings

Postby Keyz » Thu Dec 17, 2009 12:11 am

Repairman77 wrote:Update...
It would appear that the 3 main sensors, temperature, pressure and humidity are all affected by the other functions; for example the pressure is affected by temperature and humidity, the temperature by humidity, and the humidity by outside temperature. Hence Pressure can be up to +/- 1mB, Temperature +/- 1 degree C, and humidity (difficult to measure at the best of times) by several %.


Just reviewing most of your informative posts repairman, and thought that I'd just add a little more info.

The pressure is guaged from the receiver/screen unit. I know this because my transmitter stopped working, and therefore the rain, wind and outdoor temp/hum were all showing flat line.

Thus the pressure should in theory only be affected by the indoor temperature reading, according to your logic. Any link to outdoor variances is probably coincidental.

Of course, now thinking of it, you could have been comparing to calibrated seperate guages to tell the variances.

Luckily I mainly got the unit to tell wind direction (which is also only vague at best unfortunately) so a few % on each measurement is neither here nor there for me.

I hope that provides a little more info to your understanding of the unit.

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Repairman77
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Weather Station: WH1080
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Re: WH1080 Station Settings

Postby Repairman77 » Thu Dec 17, 2009 8:40 am

The pressure is gauged from the receiver/screen unit. I know this because my transmitter stopped working, and therefore the rain, wind and outdoor temp/hum were all showing flat line.

Yes indeed it is Keyz, but like all the sensors in these budget units it's very unlikely that any of them are temperature compensated like some pro units costing thousands. If you have the heating off at night and the room temperature varies by 10 degrees or more, I'm sure this affects the pressure one.

I think at the end of the day we are unfortunately expecting a little too much of these units. I've spent quite a time checking the various readings against manual equipment and at best (even after calibration on Cumulus) I think you'll be very lucky to get within +-2% of manual readings.

The rain gauge is probably the worse due to it's design. It never registers very small amounts as the rain sticks to the top before dropping down through the slot; large amounts can be calibrated to give reasonable readings. I still collect the rain readings from a rain gauge and have been adding the multiplier factor on C1 to get it somewhere right. I'm slowly getting there.

The other problem is that for best results all the sensors need to be at a vastly different height which for many like me, like many others, is impractical, so we have to settle for a compromise.

Finally most of us on here are perhaps a little to concerned with accuracy; I can't help it as I am used to working to fine tolerances as a retired Electronics engineer and +-5% is like a nightmare situation in my brain, LOL.

I think we must accept that these instruments should be looked at as an indication rather than a scientific measurement device.

Mike.
Retired Radio and Electronics Engineer residing in Cambridgeshire, UK.

Werris Creek
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Re: WH1080 Station Settings

Postby Werris Creek » Sun Aug 06, 2017 10:48 pm

correlation2.gif
The other day it became obvious that the pressure readings from my Fine Offset WH3081 (rebadged as "PanTech") are very significantly affected by inside temperature. The kink in the inside temperature graph where the reverse-cycle air conditioner cut out for a short time due to the outside unit freezing up, has a corresponding kink in the displayed barometric pressure. The similarities in the overall shape of the two graphs is pretty clear.

I too am an electronics person with experience in instrumentation and I don't like errors. But I agree that you can't expect too much from these cheap weather stations which have to be built down to a low price.
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