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1.16.3
Relative Humidity Calibration
If you want to confirm the calibration of your RH sensor or EH-020A Temperature and Relative
Humidity probe, you can simply return it to your authorized sales representative or perform
your own field test using the special adjustment provisions in TrendReader software.
Recommended methods of calibration include using an accurate relative humidity test
chamber or by mixing saturated salt solutions. Both tests are performed at an ambient room
temperature of 20 to 25°C (68 to 77°F).
RH Chamber Test
If you intend to use a Relative Humidity Test Chamber for your calibration, make sure it has
been recently tested to within ±1%. The procedure to calibrate is as follows:
1.
Set up your humidity data logger with a sample rate of 20 seconds, and equation 81 on
the RH channels. Make sure you have selected Normalized Byte data units. If you are
calibrating an EH-020A module, ensure it is properly connected to the logger, and the
external RH and temperature channels are enabled.
2.
Start the test chamber at 5% RH and place your logger (SmartReader Plus 2 or 4) or
EH-020A probe into the test chamber. Wait 20 minutes.
3.
Adjust the chamber to 20% RH and wait for 20 minutes. The wait is necessary to ensure
the chamber has adequate time to settle in at the desired level.
4.
Adjust the chamber to 80% RH and wait an additional 20 minutes.
5.
Remove your logger or RH module from the test chamber and backup the recorded
information to your computer. If you are working with more than one logger, use the
serial number as the file name to help match the data with the logger when you make
calibration adjustments.
6.
Call up the graph on your computer using TrendReader. The profile you see should
reflect the test you have just performed.
7.
Zoom in on the section that relates to the 20% RH level in the test chamber. Use the
mouse to find the byte value recorded during the latter part of the test (refer to step 3).
Record this as the "b
8.
Zoom in on the section that relates to the 80% RH level in the test chamber. Again, use
the mouse to find the byte value recorded at the end of the test (refer to step 4). Record
this value as the "b
9.
Switch to the Setup window in TrendReader software.
10. Use the following equation to calculate the "Low" calibration adjustment value:
Low = (63 x b
11. For the "High" calibration adjustment value use the following equation:
High = 40 x (-107 / (b
12. Now enter the same values by revising the logger file and view the corrected graphs.
Copyright © 2010 ACR Systems Inc. All Rights Reserved.
" reading.
L
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H
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SmartReader Plus Data Logger
76
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Troubleshooting
