Strange Humidity Calibration Results

[Ken22]

My humidity readings are very far off from reality. Replacing the sensor with a new one didn't help much. I am now told that these Oregon sensors have a long history of inaccuracy.

I'm fixing this the best I can with a combination of calibration adjustments.

I have a Multiplier of 0.776 and an offset of 22. I also have the parameter of change 98% humidity to 100% checked.

With the WMR-968 showing 98% humidity, I should get (98 * .776) + 22 which equals 98.048 and should show as 100% in Cumulus. However, Cumulus is showing 99%.

If I change the multiplier to .775 and turn off the 98->100 flag, the result should be 97.95% and show in Cumulus as 98%, but it shows as 97%.

Am I misunderstanding something, or is this a program error?

Ken
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[steve]

Cumulus truncates the result of applying the multiplier and the offset. You could argue that it should round, and I would have some sympathy with that, but it doesn't, and I don't propose to change that, in Cumulus 1 at least. It's possible that there was a reason for doing it this way.

The 98->100 setting affects the value before the multiplier and offset are applied. It is intended to cater for the deficiency in the station where the raw figure from the station can never be more than 98.

[Ken22]

The 98->100 setting affects the value before the multiplier and offset are applied. It is intended to cater for the deficiency in the station where the raw figure from the station can never be more than 98.

First, let me say that I don't really care a lot about this, so I not suggesting you spend any time fixing anything. However, the statement quoted does not appear to be correct. In my case, the value before corrections was 98 and it displayed 99 with the 98>100 setting in effect.

Ken
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[steve]

However, the statement quoted does not appear to be correct. In my case, the value before corrections was 98 and it displayed 99 with the 98>100 setting in effect.

A reading of 98 with the 98->100 setting in effect is first converted to 100. A multiplier of 0.776 and an offset of 22 applied to that = (100*0.776) + 22 = 77.6+22 = 99.6. Truncating gives 99.

[Ken22]

A reading of 98 with the 98->100 setting in effect is first converted to 100. A multiplier of 0.776 and an offset of 22 applied to that = (100*0.776) + 22 = 77.6+22 = 99.6. Truncating gives 99.

Got it!

Ken
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