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My model 450, 250, or 150 logger shows 20.7% humidity in error
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Last Updated
10th of January, 2012

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The RH sensor has two leads (wires) which are inserted into small sockets on the circuit board of the 450.  If one of the leads is not tightly in its socket, the humidity sensor will read 20.7% RH.  Temperature expansion and contraction can cause the problem to appear and then disappear.  If the RH always reads 20.7%, then check for a broken lead, or one completely separate from its socket.


Open the case, and locate the RH sensor.  It is a blue object with a grille over the white sensor within, and should be behind the openings cut in the end of the logger case.  Its leads can be pushed into their sockets using needle-nosed pliers.  This should correct the problem.

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