9.1 Troubleshooting
Symptom: Relative Humidity is reported as –9999, NAN, –40 °C, or 0%
1. Check that the sensor is wired to the correct analog input terminals as specified by the
measurement instructions.
2. Verify the range code for the single-ended measurement instruction is correct for the data
logger type.
3. Verify the red power wire is correctly wired to the 12V or SW12V terminal. The terminal the
wire is connected to will depend on the data logger program.
Connect the red wire to a 12V terminal to constantly power the sensor for troubleshooting
purposes. With the red wire connected to 12V, a voltmeter can be used to check the output
voltage for temperature and relative humidity on the yellow and blue wires respectively
(temperature °C = mV • 0.14 – 40.0; relative humidity % = mV • 0.1).
Symptom: Incorrect temperature or relative humidity
1. Verify the multiplier and offset parameters are correct for the desired units (
(p. 8)).
9.2 Maintenance
The EE181 probe requires minimal maintenance, but dust, debris, and salts on the filter cap will
degrade sensor performance. Check the metal mesh filter on the end of the sensor for debris. If
dirt or salt is engrained into the filter, it should be cleaned with distilled water or replaced. For
particularly stubborn contamination, swish the entire probe tip in isopropyl alcohol (rubbing
alcohol) and rinse off with distilled water. Make sure the filter is connected firmly with your
fingers — do not over tighten.
Check the radiation shield monthly to make sure it is free from dust and debris. To clean the
shield, remove the sensor from the shield. Dismount the shield. Brush all loose dirt off. If more
effort is needed, use warm, soapy water and a soft cloth or brush to thoroughly clean the shield.
Allow the shield to dry before remounting.
Replace filters that cannot be successfully cleaned. To replace the filter, unscrew the filter from
the probe and pull it straight away, being careful not to bend or damage the sensors. Before
putting on the replacement filter, check the alignment of the sensors with the probe, and if
necessary, carefully correct the alignment before installing the filter.
EE181 Temperature and Relative Humidity Probe
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