Load Cell Wiring & Troubleshooting Flashcards
7 cards from real CST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Load Cell Wiring & Troubleshooting flashcards as text
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.