Campbell EE181, Instruction Manual

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Model EE181 Temperature and Relative Humidity Probe
12
temperature and relative humidity are measured, both the signal reference and
power ground are connected to ground at the datalogger. The signal
reference/power ground lead serves as the return path for 12 V. There will be a
voltage drop along this lead because the wire itself has resistance. The EE181
draws approximately 1.2 mA (worst case) when it is powered. The wire used in
the EE181 (pn 9721) has resistance of 25.67 Ω/1000 feet. Using Ohm’s law,
the voltage drop (V
d
), along the signal reference/power ground lead, is given
by Eq. (1).
𝑉𝑉
𝑑𝑑
= 𝐼𝐼 • 𝑅𝑅
= 1.2 mA • 25.67 Ω 1000 ft
⁄
(1)
= 30.804 mV 1000 ft ⁄
This voltage drop will raise the apparent temperature and relative humidity
because the difference between the signal and signal reference at the datalogger
has increased by V
d
.
9. Toubleshooting and Maintenance
All factory repairs and recalibrations require a returned materials
authorization (RMA) and completion of the “Declaration of
Hazardous Material and Decontamination” form. Refer to the
Assistance page at the beginning of this manual for more
information.
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 channels as
specified by the measurement instructions.
2. Verify the voltage range code for the single-ended measurement
instruction is correct for the datalogger type.
3. Verify the red power wire is connected to the 12V or SW12V terminal.
4. A voltmeter can be used to check the output voltage for temperature and
relative humidity on the brown and white wires respectively (temperature
°C = mV • 0.1 – 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
(Section 7.2.1 , VoltSE() Instruction
(p. 7)
) and temperature range.
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)
NOTE