Weather station that always show 20% RH

Relative Humidity Sensor. Detail in weather stations that live only about couple of years. It looks like:
Old_RH_Sensors

Size may vary. It may have different number of black lines but it always work same way and got broken same way. Special coating on sensor getting old and disappear. When it happened there is always RH=20% on weather station display. Why not RH=0%? Because this type of sensors cannot measure RH lower than 20%. Therefore, when it got broken there is ~20% RH on display.

RH Sensor must be replaced to fix the issue.

Before RH Sensor replaced
Oregon_RMR500_RH_Broken2

After RH Sensor replaced
Oregon_RMR500_RH_fixed2


Repairing Oregon Scientific RMR500
Oregon RMR500 disassemble

First RH Sensor is on the mainboard

Oregon RMR500 mainboard

Second on external indoor module
Oregon RMR500 indoor module

Third on external module
Oregon RMR500 outdoor module

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3 Comments

  1. I’ve been using RMR500 for years, worked perfectly until about two weeks ago. Now, the “main unit” readings do not update at all, only refresh once upon reset.

    Have any ideas? Did you go further with this device in your research? Is it possible to disassemble the main device without damaging it?

    1. I only know permanent 20% humidity reason. If there is no temperature changes on “Main unit” that is definitely another issue.

      I did disassemble the main unit and assemble it later . Looks good. Work perfect. The only problem is to get decorative square plastic border removed. It is attached using adhesive tape. So there is need to put some force to remove it. Using metal tools like screwdriver is bad idea since it might leave some traces on a surface.

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