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
Which symptom most strongly suggests moisture ingress into a load cell or junction box?
Answer: Erratic, drifting zero with no applied load
Moisture causes leakage currents across the bridge circuits, producing an unstable, drifting zero reading.
What is the purpose of a shielded cable in load cell wiring?
Answer: To reduce electromagnetic interference (EMI) on the signal lines
Shielding surrounds the signal conductors and is grounded at one end to divert induced EMI noise away from the load cell output.
During troubleshooting, a technician finds that shorting the signal wires together causes the indicator to read exactly zero. What does this confirm?
Answer: The indicator and its wiring back to the junction point are functioning correctly
Shorting the signal inputs confirms the indicator circuit reads zero when given a true zero-differential input, isolating the fault to the load cell side.
What value should the input resistance (signal+ to signal−) of a healthy 350 Ω load cell measure?
Answer: Approximately 350 Ω
For a 350 Ω load cell, the signal bridge output resistance (input resistance) is nominally 350 Ω when measured across the signal terminals with excitation disconnected.
Which load cell specification directly describes the maximum combined error from non-linearity, hysteresis, and repeatability?
Answer: Combined error or accuracy class
Combined error (accuracy class) is the single specification that encompasses non-linearity, hysteresis, and repeatability as a percentage of rated output.
A technician suspects a load cell cable has a wire-to-shield short. Which test will confirm this?
Answer: Measure resistance from each conductor to the shield with the cell disconnected
Measuring resistance from each conductor to the shield with the load cell disconnected directly reveals any wire-to-shield fault.
What is the effect of connecting the cable shield at both ends (indicator and load cell) in a noisy industrial environment?
Answer: Creates a ground loop that can introduce noise and hum
Grounding a shield at both ends allows circulating ground loop currents induced by potential differences to flow through the shield and couple noise onto signal wires.