Introduction: Troubleshooting Load Cell Bridge Circuit and Wiring Connections
Damages in wire connection are one of the most common faults of a load cell. Troubleshooting load cell bridge circuit is the basic checkings before contacting support or sending it for service.
The following steps are suitable for troubleshooting strain gage based four wire load cell. please refer the data sheet to find the type of your load cell or contact vendor.
See the image of single point load cell - SreeKa make, which is a strain gage based four wire load cell sensor.
Required Tools and materials
- Multimeter
- Load cell (which has to be trouble shooted)
- Data sheet or user manual of the load cell
Step 1: Four Wire Load Cell
please see the reference four-wire load cell bridge circuit. check the link for troubleshooting load cell bridge circuit of six-wire
Step 2: Setting Up Multimeter
Set the multimeter to resistance mode as shown in the image and verify it by shorting the probes. Multimeter should read somewhere around 0.03 ohms.
Step 3: Input Impedance Checking
Check Excitation +Ve to Excitation –Ve
From the datasheet of this load cell, input impedance should be 350 Ω ± 1%. The measured value is within specified value. If measured value is 353.5 ohms, recorded it and load cell has to be sent for service
Step 4: Output Impedance Checking
Check Output +Ve to Output –Ve
As per the datasheet, for this load cell, input impedance should be 350 Ω ± 1%. The measured value is within specified value. If measured value is 353.5 ohms, recorded it and load cell has to be sent for service
Step 5: Checking Insulation Failure Between Signal Wire to Ground
Check short between signal wires to the ground wire by connecting the multimeter probes as shown in the image. The multimeter should indicate a higher value of somewhere above 5000 MΩ or OL. If the measurement is in few ohms then there is a short in the signal wire to ground wire which may cause load cell to malfunction.
Do this checking between each signal wire to ground wire
Step 6: Checking Insulation Failure Between Signal Wires to Load Cell Body
Check short between signal wires to the ground wire by connecting the multimeter probes as shown in the image. The multimeter should indicate a higher value of somewhere above 5000 MΩ or OL. If the measurement is in few ohms, then there is a short in the signal wire to load cell body, which may cause load cell to malfunction.
Do this checking between each signal wire to body
