Relative Humidity Calibration; Specifications - ACR Electronics SmartReader Plus Reference Manual

SmartReader Plus Data Loggers
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That is because the body readily gives off heat and moisture that is especially
noticeable at lower RH levels.
· The time taken between slinging the psychrometer and reading it can exhibit several
degrees of inaccuracy in the wet bulb reading. Air currents around the body, whether it
is slung in the shade of a building or in sunlight, not knowing how to tie the wet sock, its
condition, and the purity of water used, all contribute to error. In addition, interpolating
the data from a psychrometric chart can add another 2 to 4% to the accumulative error.
1.4.5

Relative Humidity Calibration

Each relative humidity sensor has been individually calibrated in an environmental chamber
with standards traceable to the National Institutes of Standards and Technology (NIST).
The SmartReader Plus 2 and the EH-020A probe are supplied with a calibration certificate
which provides calibration values. These calibration values must be entered and stored in the
logger during initial setup. If your RH sensor is out of calibration, you can simply replace it with
a new one.
NOTE: A straight replacement of the RH sensor will introduce an additional +2%
tolerance on the RH accuracy. Calibration of the RH channel with the new RH
sensor is recommended.
In the event that you wish to confirm the RH calibration of your sensor, you can perform your
own field test.
information on RH testing.
Interchangeable replacement RH sensors for loggers are available through your dealer. For
best accuracy, it is recommended these be calibrated together with the logger - consult your
ACR representative for price and availability of this service. Replacement EH-020A modules
which are pre-calibrated are available through your dealer.
1.4.6

Specifications

Relative Humidity Sensor & EH-020A
Type:
Range:
Accuracy:
Resolution:
Response Time:
Environmental Conditions:
Refer to Appendix B Temperature and Relative Humidity Calibrations
Capacitive thin polymer film
0 to 95% (non-condensing)
±3% RH from 10 to 90% (-20 to 40°C [-4 to 104°F])
Better than 0.04% between 25 and 60% RH at 25°C (77°F)
Adequate ventilation reduces the response time which is
approximately five minutes in still air.
The RH sensor is relatively immune to chemical
contamination but when exposed to extreme environmental
conditions, accuracy degradation could result. For long-term
stability and reliable readings, the sensor should not be
subjected to liquid immersion or exposed to high
concentrations of organic solvents, corrosive agents, sulfur
gases and strong acids or bases. Dust settling on the sensor
surface will not affect sensor performance except possibly to
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