Introduction: Troubleshooting Load Cell Bridge Circuit and Wiring Connections

Picture of 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

  1. Multimeter
  2. Load cell (which has to be trouble shooted)
  3. Data sheet or user manual of the load cell

Step 1: Four Wire Load Cell

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Comments

DIY Hacks and How Tos (author)2016-10-16

Nice. It is always important to be able to fix your electronics.

Yes. the fault could be in electronics also. in this instruction I covered only for troubleshooting load cell.