Adam Equipment WBZ Series Service Manual page 8

A method to check the basic function and integrity of a load cell can be done using a
ohmmeter and voltmeter with up to a 10volt power supply.
Before the load cell is connected to the power supply use the ohmmeter to measure the
resistance between the wires. Typical resistance values are:
+E to -E
+S to -S
+E to +S or any other combination similar approximately 270 ohms.
If the load cell has Sense connections in addition they are connected to the excitation
internal to the load cell.
Connect the load cell +E and -E to a power supply, typically 10 volts. Never use more
than 12 volts as it may damage the load cell.
Measure the voltage between +S and -S.
With no load the voltage should be approximate 0mv ±3mv.
With a mass on the load cell the output voltage should increase. The amount by which it
increases will be dependent upon the sensitivity of the load cell, capacity of the load cell,
the excitation voltage and the amount of mass placed on the load cell. Most load cells
have a sensitivity of either 2mv/V or 3mv/V.
The expected change to the output is:
Vout = (2mv/V) * Vext * Mass
capacity of load cell
For example a 2mv/V load cell of 30Kg capacity with 20Kg placed on it. Vext is 5 volts
would give a output of approximately:
© Adam Equipment Company 2008
410 ohms ±30 ohms
350 ohms ± 2 ohms
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