Instruction Manual VGC301 Controller
InstruTech, Inc.
Page 22
7.1
Log 1-8; Log-Linear Analog Output Equation & Table - Torr
Log-Linear 1 to 8 V analog output for selected gases - Engineering units in Torr
True Pressure
(Torr)
N
2
Ar
He
O
2
CO
2
Kr
Freon12
Freon22
D
2
Ne
CH
4
0.0001
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
0.0002
1.301
1.301
1.301
1.301
1.301
1.301
1.301
1.301
1.301
1.301
1.301
0.0005
1.699
1.699
1.699
1.699
1.699
1.477
1.699
1.699
1.699
1.699
1.699
0.0010
2.000
1.845
1.903
2.000
2.041
1.602
2.176
2.176
2.114
1.845
2.230
0.0020
2.301
2.146
2.204
2.301
2.362
2.000
2.491
2.491
2.380
2.176
2.519
0.0050
2.699
2.519
2.602
2.699
2.643
2.362
2.881
2.845
2.778
2.544
2.886
0.0100
3.000
2.820
2.908
2.987
3.041
2.681
3.167
3.130
3.083
2.851
3.185
0.0200
3.301
3.117
3.207
3.297
3.346
2.978
3.476
3.435
3.386
3.149
3.483
0.0500
3.699
3.511
3.607
3.692
3.740
3.371
3.860
3.839
3.778
3.542
3.888
0.1000
4.000
3.808
3.914
3.988
4.029
3.670
4.155
4.134
4.083
3.845
4.201
0.2000
4.301
4.100
4.217
4.288
4.322
3.960
4.439
4.418
4.398
4.149
4.498
0.5000
4.699
4.494
4.638
4.687
4.689
4.336
4.786
4.774
4.837
4.555
4.893
1.0000
5.000
4.778
4.973
4.987
4.978
4.602
5.021
5.017
5.190
4.872
5.204
2.0000
5.301
5.057
5.346
5.288
5.233
4.845
5.210
5.220
5.616
5.201
5.522
5.0000
5.699
5.389
6.130
5.697
5.524
5.107
5.389
5.418
7.391
5.719
5.877
10.0000
6.000
5.602
8.041
6.013
5.696
5.250
5.471
5.530
8.041
6.332
6.446
20.0000
6.301
5.763
8.041
6.348
5.819
5.360
5.521
5.571
8.041
7.766
7.550
50.0000
6.699
5.895
8.041
6.890
5.915
5.410
5.579
5.617
8.041
8.041
7.925
100.0000
7.000
5.946
8.041
7.320
5.966
5.438
5.670
5.691
8.041
8.041
8.041
200.0000
7.301
5.991
8.041
7.470
6.090
5.521
5.777
5.808
8.041
8.041
8.041
300.0000
7.477
6.053
8.041
7.580
6.228
5.555
5.838
5.876
8.041
8.041
8.041
400.0000
7.602
6.130
8.041
7.686
6.350
5.595
5.883
5.925
8.041
8.041
8.041
500.0000
7.699
6.207
8.041
7.781
6.458
5.624
5.918
5.964
8.041
8.041
8.041
600.0000
7.778
6.274
8.041
7.863
6.561
5.647
5.947
5.998
8.041
8.041
8.041
700.0000
7.845
6.338
8.041
7.934
6.664
5.667
5.974
6.029
8.041
8.041
8.041
760.0000
7.881
6.375
8.041
7.974
6.732
5.677
5.989
6.045
8.041
8.041
8.041
800.0000
7.903
6.400
8.041
7.999
6.774
5.685
5.998
6.057
8.041
8.041
8.041
900.0000
7.954
6.455
8.041
8.041
6.900
5.698
6.021
6.079
8.041
8.041
8.041
1000.0000
8.000
6.512
8.041
8.041
7.045
5.706
6.045
6.104
8.041
8.041
8.041
Values listed under each gas type are in volts.
The log-linear output signal and pressure are related by the following formulas:
P = 10
(V - 5)
V = log
10
(P) + 5
where P is the pressure in torr, and V is the output signal in volts.
An analog output of 10 volts indicates a faulty convection gauge or unplugged gauge cable.
The chart on the following page shows the graphical results of the table and formulas given above for nitrogen.
True pressure (N
2
) is plotted on the X-axis with a log scale. The output signal is plotted on the Y-axis on a linear
scale.
Note - when using the units of pascals and LOG 1-8 is selected , the same equation of
P = 10
(V - 5)
listed above
applies. This results in a log-linear analog output range of 1 to 10.12 Vdc for 1.30E-02 pascals to 133 kpa.