Basic load cell resistance checks
Unfortunately there is no standard wiring colour code for load cells so you will need to know from data
supplied with the cell which wires are the excitation wires and which wires are the signal wires (see section
2.6 for colour code examples). If you do not have this information then as shown in the diagram above in
addition to the 4 resistance elements which make up the Wheatstone bridge there are commonly one or two
resistors in the excitation lines. This means that the resistance across the excitation wires is usually the
highest resistance measured across any two wires. The resistances also vary between manufacturers and
load cell types, input and output resistance values are often provided in the data supplied with the load cell.
To test the cell obtain a meter capable of measuring Ohms, measure across each pair of wires in turn
and record the results (space provided in the table which follows). The load cell must be completely
disconnected from the monitor and at no load when these tests are made.
The table which follows gives measurements taken with a sample 350Ωload cell with one resistor in its
Ex+ line i.e. these readings show lowest values between signal lines and Ex-. For a load cell with two
resistors in its excitation lines (one in Ex+ and one in Ex-) you would expect the Ex+ and Ex- to S+ and SPage
measured values to be roughly the same. In a typical load cell the S+ to S- should be close to the specified
output resistance of the cell i.e within an one or two Ohms, other values are nominal.