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 is the purpose of the 'creep' specification on a load cell datasheet?
Answer: It describes output change under constant load over time
Creep is the change in load cell output occurring with time while under a constant load, expressed as a percentage of rated output.
A four-wire load cell reads correctly at low loads but becomes increasingly non-linear at higher loads. Which cause should the technician investigate first?
Answer: Mechanical binding or side loading on the load cell
Non-linearity that increases with load often indicates mechanical binding, off-axis loading, or structural interference affecting the cell's freedom of movement.
What is the function of a 'summing card' (summing junction board) in a multi-load-cell installation?
Answer: Electrically combines the outputs of multiple load cells into a single signal for the indicator
A summing junction board connects multiple load cells in parallel and provides trim adjustment potentiometers to equalize their contributions before sending a single summed signal to the indicator.
Which test is used to verify that a load cell's insulation has not been compromised by moisture or cable damage?
Answer: Insulation resistance (IR) test with a megohmmeter
An insulation resistance (IR) test applies a DC voltage (typically 50–100 V) between the conductors and the cable shield/ground to check for insulation breakdown caused by moisture or damage.
What should a technician do before disconnecting load cell wiring in an active weighing system?
Answer: Power down the indicator and lock out/tag out the system
Lockout/tagout (LOTO) procedures must be followed before disconnecting any wiring to prevent unexpected energization and ensure technician safety.
When a load cell output drifts slowly upward over 30 minutes with no change in applied load, which environmental factor is most likely the cause?
Answer: Thermal effects — the load cell or structure is gradually heating up
Slow, unidirectional drift over minutes under constant load is a classic symptom of thermal expansion in the load cell or mounting structure as temperature stabilizes.
What is the correct procedure for verifying load cell rated output (sensitivity) in the field without a calibration standard?
Answer: Apply certified deadweights equal to rated capacity and measure the mV output with a precision meter
Applying certified deadweights equal to the rated capacity and measuring the resulting mV output directly verifies the load cell's actual sensitivity against its datasheet specification.