Load Cell Wiring & Troubleshooting Flashcards

What condition is indicated when the output of a load cell under no load reads a large positive mV value that cannot be zeroed by the indicator?

Answer: Overload or permanent mechanical damage to the cell

A large, unzeroed offset beyond the indicator's zero-tracking range suggests the load cell has been overloaded and the strain gauges have been permanently deformed.

In a 4-20 mA transmitter-style load cell system, what reading on a current loop meter indicates an open-circuit fault in the loop wiring?

Answer: 0 mA

An open circuit in a 4-20 mA loop causes current flow to stop completely, reading 0 mA, which is below the live-zero of 4 mA.

What is the recommended grounding practice for the cable shield when using a load cell with a digital weight indicator?

Answer: Ground the shield at the indicator end only

Grounding the shield only at the indicator (instrument) end prevents ground loop formation while still providing EMI protection.

When performing a deadweight test on a scale with load cells, a technician notices the reading is stable but 2% low across all weights. The most likely cause is:

Answer: Incorrect span calibration or wrong sensitivity entered

A consistent percentage error across all weights is a span (gain) problem, caused by incorrect calibration or an incorrect mV/V sensitivity value.

What does the specification 'IP68' on a load cell indicate regarding its suitability for wiring in washdown environments?

Answer: It is sealed against continuous immersion in water

IP68 means the load cell is dust-tight and protected against continuous immersion in water, making it suitable for washdown and submersible applications.

A technician replaces one load cell in a 4-cell platform but the corner that was repaired now reads high. The most appropriate corrective action is:

Answer: Adjust the trim potentiometer for that cell in the junction box

Corner errors after a single cell replacement are corrected by trimming that cell's contribution via the junction box potentiometer.

Which fault causes a load cell system to exhibit high noise (fluctuating digits) only when heavy machinery nearby is running?

Answer: Inadequate EMI shielding or poor shield grounding

Electromagnetic interference from nearby motors or machinery couples into unshielded or poorly grounded signal cables, causing noise correlated with equipment operation.