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Chapter 3: Calculating the gain resistor value
The ICA3 and ICA6 are ± 10V Strain Gauge Amplifiers.
They are supplied un-calibrated but optimized for a sensitivity of 2.5mV/V. To accommodate other sensitivities the
gain resistor 'R' as shown in Figure 2.2, can be changed according to the following formula.
N.B. a high quality component e.g. 1% 25 ppm metal film resistor should be used for optimum performance (the 'H'
versions should use 10-15 ppm metal film devices to maintain their performance). It may be necessary to use an E96
value to optimise the trim range:-
Table 3.1 ICA3 and ICA6 (±10 Volts)
Gain
=
372
(required mV/V)
e.g. 1
For 2.5 mV/V
(Factory setting):-
e.g. 2
For 0.5 mV/V
e.g. 3
For 5.0 mV/V
N.B If an output other than ± 10V is required e.g. ±5V then reduce the gain calculation in proportion i.e. for ±5
Volt
Gain
=
372
(required mV/V)
e.g.1
For 2.5 mV/V
(Factory setting):-
Mantracourt Electronics Limited ICA3 & 6 S and H Versions User Manual
R
Gain
= 149 x
R= 270 Ohms
Gain
= 744 x
R= 53.8 Ohms
Gain
= 74.4 x
R= 545 Ohms
x
5
10
Gain =
74.4x
=
40,000
Ohms
(Gain-1)
(Use preferred value 270R)
(Use preferred value 53.6R E96)
(Use preferred value 549R E96)
R =
40,000
Ohms
(Gain-1)
R = 545 Ohms
(Use preferred value 549R E96)
7
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