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Strain Gauge Sensitivity Adjustment (DSC ONLY)
Standard unit suitable for inputs up to 3m/V. Beyond this strain gauge sensitivity adjustment please consult factory.
If your strain gauge does not deliver a 2.5mV/V full scale output, you may want to adjust the sensitivity of the
electronics (hardware) and/or the software gain controls.
If you want to test with an input of more than 2.5mV/V, you will have to adjust the hardware sensitivity to avoid
saturating the input. If it is less, you can correct in software alone, but increasing sensitivity will generally improve
accuracy.
To adjust the mV/V for DSC, an extra resistor 'Rg' is fitted across the pads RG, as shown above, in
Identifying the DSC 'Rg' Resistor
Identifying Sensor End Connections
The link across TC can be cut to disconnect the internal 100R gain resistor: This is needed for lowering the
sensitivity.
The resistor is 0805 size surface mount chip.
A 0.1%, 5ppm/Deg C resistor for the high stability version & 25ppm/ Deg C for the Industrial must be used to
maintain performance.
Reducing Sensitivity
To accommodate a maximum sensor output larger than 2.5mV/V, it is necessary to reduce the electrical sensitivity
of the input circuitry.
To decrease sensitivity, the link TC is cut, and the value of the resistor fitted, in Ω, should be –
R
= (required mV/V) x 40
g
Example: For 10mV/V
R
= 10 x 40 = 400Ω
g
Increasing Sensitivity
When the full-scale output is smaller than 2.5 mV/V, it may be desired to increase sensitivity. However, it is often
possible instead to compensate partly or entirely in software, by increasing a software gain control CGAI or SGAI
To increase sensitivity, TC is left in place, so that the fitted Rg appears in parallel (this gives better temperature
stability). Its value should then be
RG = 1 / (( 0.025 / rqd m V/V ) – 0.01)
Two effects should be noted
1. The purpose of increasing sensitivity is to reduce reading noise, which governs the effective resolution. Using
software gain alone obviously gives reduced performance.
2. The sensitivity should, however, not be set greater than typically 1mV/V: Beyond this, input noise usually
dominates and no extra benefit can be achieved.
67
Micron Meters
RGG
TC
DCell & DSC User Manual
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