TROUBLESHOOTING LOAD CELLS

If it is suspected that a load cell is bad it will usually be possible to identify the bad load cell

Compression load cell.

Compression load cell.

using a digital multi-meter to measure six different resistance valves on the load cell. Before measuring the load cell resistance values, check all connections in the junction box, the plug and the receptacle, to insure there are no loose or shorted wires.
NOTE: A digital multi-meter with an ohms scale will be required to make the measurements.
Step 1: Open the load cell junction box and disconnect all the load cell wires from the terminal strip.
Step 2: Fill in the resistance values for each load cell.
Step 3: If the bad load cell has not been identified in steps one and two, continue with the following procedure:
Reconnect ONE of the load cells to the terminal strip observing the color codes. Fill in the reading shown on the digital read.
Disconnect the first load cell and repeat step A for each load cell. It will usually be obvious by looking at the readings you have recorded in the table which load cell is bad.
1. White to Green (- signal to + signal: output resistance): This value should be 350 ± 1.
2. Red to Black (+ excitation to – excitation: input resistance): This value may vary from one load cell to another as a result of the compensating resistors in the excitation legs of the load cell. Normal values range from 375 to 435.
3. Red to Green (+ excitation to + signal) and Red to White (+ excitation to – signal): It is important that these two readings be the same within one ohm. These values may vary from one load cell to another as a result of the compensating resistors in the excitation leg of the load cell. Normal values range from 280 to 310.
4. Black to Green (- excitation to + signal) and Black to White (- excitation to – signal): It is important that these two readings be the same within one ohm. These values may vary from one load cell to another as a result of the compensating resistors in the excitation leg of the load cell. Normal values range from 280 to 310.