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294 Properties of the Modules

6.7.1.1 Full bridge

A full bridge has four resistors, which can be four

correspondingly configured strain gauges or one

complete sensor which is a full sensor internally.

The full bridge has five terminals to connect. Two leads

+VB(C) and -VB(D) serve supply purposes, two other leads

+in (A) and -in(B) capture the differential voltage. The

fifth lead sense(F) is the Sense lead for the lower supply

terminal, which is used to determine the single-sided

voltage drop along the supply line.

Assuming that the other supply cable +VB(C) has the

same impedance and thus produces the same voltage

drop, no 6th lead is needed. The Sense lead makes it

possible to infer the measurement bridge's true supply

voltage, in order to obtain a very exact measurement

value in mV/V.

Please note that the maximum allowed voltage drop along a cable may not exceed approx. 0.5 V. This

determines the maximum possible cable length.

If the cable is so short and its cross section so large that the voltage drop along the supply lead is

negligible. In this case the bridge can be connected at four terminals by omitting the Sense line.

6.7.1.2 Half bridge

A half bridge may consist of two strain gauges in a circuit

or a sensor internally configured as a half bridge, or a

potentiometer sensor. The half bridge has 4 terminals to

connect. For information on the effect and use of the

Sense lead sense (F), see the description of the full bridge.

The amplifier internally completes the full bridge itself, so

that the differential amplifier is working with a genuine

full bridge .

Note

It is important that the measurement signal of the half

bridge is connected to +IN (A). The IN (B) access leads to

implausible measured values and influences the

neighbor channels.

294

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