Load cells are essential for precision in measurement applications, but problems can occur, affecting performance. This troubleshooting guide provides a systematic approach to diagnose and resolve common issues, ensuring your load cell operates efficiently. 

Follow instructions below to identify and repair potential issue with the load cell. It is recommended that the malfunctioning load cell is removed from the application assembly prior to diagnosing the failing condition. Perform the initial check described next to the condition experienced in application. If condition is confirmed, perform the actions listed to identify potential root cause. If condition of load cell is found to have improved, continue to the Application Troubleshooting section.

Identify the Issue 

What problem are you experiencing with the load cell?

Common Issues and Actions

Zero Balance is Out of Specification

Potential Root Causes: 

Excessive load causing plastic deformation. 

Physical damage to thin-film strain gauges. 

Exposure to high temperatures. 

Check: 

Measure voltage output between -OUT and +OUT using a 10V supply at +EXC and -EXC leads. 

Measure resistance across input (+EXC, -EXC) and output (+OUT, -OUT) leads. 

Inspect thin-film surfaces under 5X magnification for scratches, nicks, or discoloration. 

Solution: 

If zero balance stabilizes with exercise, recalibrate and use with the new zero balance. 

Replace the load cell if deformation, discoloration, or encapsulant damage is present. 

Unstable Zero Balance

Potential Root Causes: 

Excessive load causing structural damage. 

Vibration or instability in the assembly. 

Grounding issues or intermittent electrical connections. 

Check: 

Measure resistance across input and output leads. 

Inspect cable continuity by moving the cable and monitoring output changes. 

Ensure assembly stability and proper grounding. 

Solution: 

Stabilize the assembly to eliminate vibrations. 

Repair or replace cables with continuity issues. 

Replace the load cell if damage persists. 

Zero Balance Measures Volts Instead of Millivolts

Potential Root Causes: 

Improper wiring of the load cell. 

Open, shorted, or intermittent connections. 

Check: 

Verify that load cell wiring matches system schematics. 

Measure resistance across input and output leads to identify open or short circuits. 

Solution: 

Correct the wiring and ensure proper connections. 

Replace the load cell if resistance deviates significantly from specifications. 

Output Does Not Change with Load

Potential Root Causes: 

Physical damage to strain gauges. 

Excessive pre-load restricting movement. 

Improper wiring or assembly interference. 

Check: 

Ensure proper clearance and freedom of movement for the load cell. 

Verify wiring accuracy and inspect cable continuity. 

Examine the assembly for adequate deflection under load. 

Solution: 

Adjust the assembly to prevent interference. 

Replace damaged load cells or repair wiring as necessary. 

Output at Full Scale is Out of Specification

Potential Root Causes: 

Excessive pre-load causing early overload stop. 

Assembly instability or inadequate mechanical support. 

Check: 

Ensure adequate clearance between the load cell and adjacent components. 

Verify that the assembly is stable and does not obstruct full deflection. 

Solution: 

Adjust assembly to allow full movement. 

Provide adequate mechanical support to the load cell. 

Non-Linear Performance

Potential Root Causes: 

Plastic deformation due to excessive load. 

Misalignment or load sharing with extended assemblies. 

Check: 

Measure voltage output consistency between -OUT and +OUT using a 10V supply at +EXC and -EXC. 

Inspect the assembly for alignment and support. 

Solution: 

Replace the load cell if non-linear performance persists. 

Realign the assembly to ensure proper load distribution. 

Application Troubleshooting Checklist 

If the load cell itself meets specifications, focus on the application setup: 

ZERO BALANCE IS OUT OF SPECIFICATION

Potential Root Cause

A pre-load is being applied from the extended assembly.

CHECK

Check assembly for interference of components.

Ensure weight of assembly is account for in load cell output.

Ensure torque applied at bolts/screws does not exceed SMD’s recommended torque

UNSTABLE ZERO BALANCE

Potential Root Cause

The extended assembly is unstable or vibrating. 

Electrical noise is being introduced into the output via grounding issues.

Intermittent, open, or shorted connection at lead outs.

CHECK

Ensure the extended assembly is stable and adequately secured.

Ensure the load cell is properly grounded.

Perform continuity check on the load cell cable for open or short circuits. Check cable integrity from sensor by moving
the cable and monitoring output.

ZERO BALANCE MEASURES VOLTS INSTEAD OF MILLIVOLTS

Potential Root Cause

Improper wiring of the load cell to the system.

Intermittent, open, or shorted connection at lead outs.

CHECK

Ensuring load cell wiring schematic matches expected input of the system.

Perform continuity check on the load cell cable for open or short circuits. Check cable integrity from sensor by moving
the cable and monitoring output.

Measure resistance across input leads (+EXC and -EXC) and output leads (+OUT and -OUT) for open or short circuit.

OUTPUT DOES NOT CHANGE WITH LOAD

Potential Root Cause

An excessive pre-load is being applied causing the load cell to prematurely hit the overload stop

Improper wiring of the load cell to the system

Intermittent, open, or shorted connection at lead outs.

Extended assembly is fixed and does not allow the load cell to deflect with load.

CHECK

Ensure there is adequate clearance between the load cell and the next assembly including space below and to the side of
the sensor.

Ensure that the fixturing does not excessively deflect under load.

Ensuring load cell wiring schematic matches expected input of the system.

Perform continuity check on the load cell cable for open or short circuits. Check cable integrity from sensor by moving
the cable and monitoring output.

Ensure extended assembly is free to move when loaded.

OUTPUT AT FULL SCALE IS OUT OF SPECIFICATION

Potential Root Cause

An excessive pre-load is being applied causing the load cell to prematurely hit the overload stop

Load cell is load sharing with the extended assembly.

Load cell is inadequately supported causing the mechanical ground to deflect under load.

Extended assembly does not allow the load cell to fully deflect with the full scale load applied.

CHECK

Ensure there is adequate clearance between the load cell and the next assembly including space below and to the side of
the sensor.

Ensure the extended assembly does not contact anything during the full range of motion of the load cell.

Ensure extended assembly provides adequate support during loading.

OUTPUT AT FULL SCALE IS OUT OF SPECIFICATION

Potential Root Cause

An excessive pre-load is being applied causing the load cell to prematurely hit the overload stop

Load cell is load sharing with the extended assembly.

Load cell is inadequately supported causing the mechanical ground to deflect under load.

Extended assembly does not allow the load cell to fully deflect with the full scale load applied.

CHECK

Ensure there is adequate clearance between the load cell and the next assembly including space below and to the side of
the sensor.

Ensure the extended assembly does not contact anything during the full range of motion of the load cell.

Ensure extended assembly provides adequate support during loading.

For expert support or to return a load cell for analysis, contact Strain Measurement Devices at [email protected]. Proper maintenance and troubleshooting can extend the life of your load cells and ensure consistent, accurate performance.