Tidal Engineering Synergy Series Technical Manual page 43

Vaisala HMM30C Temperature Compensation
Vaisala Relative Humidity sensors are available in temperature compensated and uncompensated versions
(HMM30C) and the Synergy Controller is compatible with both types. In addition the controller can
accommodate sensors with 0-5VDC and 4-20mA outputs.
The Synergy Controller uses the Vaisala recommended temperature compensation algorithm for the
HMM30C. The algorithm is a second order polynomial defined over four temperature ranges by the following
table of coefficients.
Where: a0, a1, b0, b1 are constants with the values as determined in the table below:
Temp Range (C)
-40...-20
-20...+15
+15...+45
+45...+180
Temp Range (C)
-40...-20
-20...+15
+15...+45
+45...+100
+100...+180
And Where:
Offset compensation:
Gain compensation:
RH Compensated = (RH Raw + A) * B
The following is a table of example temperature readings (T) and uncompensated raw relative humidity
readings (RH raw). The last column displays the compensated relative humidity reading (Vaisala RH
Corrected).
T RH a0
Raw
60 70 -1.53646
60 80 -1.53646
60 100 -1.53646
70 40 -1.53646
70 60 -1.53646
70 80 -1.53646
70 100 -1.53646
80 30 -1.53646
80 40 -1.53646
80 60 -1.53646
80 80 -1.53646
80 100 -1.53646
85 30 -1.53646
85 40 -1.53646
85 60 -1.53646
85 80 -1.53646
85 100 -1.53646
100 60 -1.53646
100 80 -1.53646
100 100 -1.53646
54 30 -1.53646
Synergy Controller Technical Manual, Revision H
Vaisala Constants
a0
-0.104980
0.469374
0.000000
-1.536460
b0
0.947370
1.050385
1.000000
0.889657
0.551922
Vaisala Temperature Compensation
a1 b0
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
0.034144 0.889657
A = a0 + b0 * T
B = b0 + b1 * T
b1 A
0.002452 0.51218
0.002452 0.51218
0.002452 0.51218
0.002452 0.85362
0.002452 0.85362
0.002452 0.85362
0.002452 0.85362
0.002452 1.19506
0.002452 1.19506
0.002452 1.19506
0.002452 1.19506
0.002452 1.19506
0.002452 1.36578
0.002452 1.36578
0.002452 1.36578
0.002452 1.36578
0.002452 1.36578
0.002452 1.87794
0.002452 1.87794
0.002452 1.87794
0.002452 0.307316
a1
-0.060009
-0.031292
0.00000
0.034144
b1
-0.008510
-0.003359
0.000000
0.002452
0.005829
B Vaisala RH
Corrected
1.036777 73.105
1.036777 83.473
1.036777 104.209
1.061297 43.358
1.061297 64.584
1.061297 85.810
1.061297 107.036
1.085817 33.872
1.085817 44.730
1.085817 66.447
1.085817 88.163
1.085817 109.879
1.098077 34.442
1.098077 45.423
1.098077 67.384
1.098077 89.346
1.098077 111.307
1.134857 70.223
1.134857 92.920
1.134857 115.617
1.022065 30.976
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