HBM MGCplus - Page 141

Measuring
Adapting to the transducer
MGCplus A0534-30.0 HBM: public 141
The resistance of the SG changes due to strain. Since this change lies in
the mΩ and μΩ range, a "Wheatstone bridge" must be used with great
accuracy.

1

2

3

4
U
A
U
B
ML10B
ML30B
ML55B
U
A
U
B
+
k
4
 @
U
A
U
B
+ relativechangeoftheexcitationvoltage
 = 







Total strain
k = strain gage sensitivity (gage factor)
U
B
= Bridge excitation voltage
U
A
= bridge output voltage

Fig. 7.1 Wheatstone bridge
You can use the MGCplus measuring system to measure the strain of one
SG or the total strain of multiple SGs. The table below summarizes the pos
sible bridge circuits and the necessary device configuration:
Bridge type Number of
active strain
gages
Total strain Connection board Amplifier
e
Quarter bridge circuit
1  AP14 ML10B, ML30B,
ML55B
1)
e
1
Half bridge circuit
e
2
2  = 



AP01i, AP03i,
AP14
ML10B, ML55B
1)
ML30B (only with AP14)
e
1
e
2
e
4
e
3
Full bridge circuit
4  = 







AP01i, AP03i,
AP14
ML10B, ML30B,
ML55B
1)
, ML38B
2
)
1)
For the combination of ML55B with AP14, a one-time zero calibration must always be performed after setting up the measurement chain.
2)
Only in combination with AP01i and AP03i