Author Topic: La Crosse C85845 accuracy?  (Read 1965 times)

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Offline EthanTX

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La Crosse C85845 accuracy?
« on: December 05, 2020, 09:36:30 AM »
Hey guys;
I just installed my bran-new La Crosse C85845 in/out thermo-hygro meter last night.
I am a bit disappointed with the accuracy of the outdoor sensor for both temp and humid.
I have an old RS 63-1030 system that is still working downstairs, but I wanted one for upstairs.
After letting the La Crosse stabilize overnight, the temp display is always about 2F higher than both the RS with its sensor mounted next to the La Crosse one, and a mercury thermometer mounted in the same general area, and about 4F higher than my Etekcity Laser non-contact IR.
The humidity reading on the La Crosse appears to be reading low; it reads only 80% with rain and temp of around 40F. Local airport is reporting 89%.

I don't suppose there is a 'hack' to calibrate the La Crosse (voiding the warranty of course).
I guess I could try to contact La Crosse tech and see if they might be willing to send me another sensor, but I strongly suspect that the next sensor won't be any more accurate than the one I've got.

Has anyone has any experience with this unit?

Thanks for your help/advice

Offline EthanTX

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Re: La Crosse C85845 accuracy?
« Reply #1 on: December 08, 2020, 08:13:08 AM »
The La Crosse C85845 accuracy is fine!
The problem was that I had installed the outdoor sensor above the back door (north facing) in such a way that about one inch of it hung below the top door jamb (the door opens inwards, so this was not an issue).
Even though the back porch is unheated, there is enough heat escaping from the house through the porch and out the back door.
Because the sensor was actually hanging below the jamb, it was picking up a stream of heat coming through the door.
After moving the sensor to a higher position, the temperature on the La Crosse matches that on the RS unit, with its sensor having always been mounted higher on the door frame.

I guess this should be a hint to me that I need to install more weather stripping on the doors into and out of the porch, as well as a window that opens out onto the porch.
Note that this porch is fully enclosed, with one door from the house and one to the outside, plus one window from the house and one to the outside.