Electrical Systems & Mechanical Components 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 Electrical Systems & Mechanical Components flashcards as text
What is the purpose of a junction (summing) box in a multi-load-cell platform scale?
Answer: To parallel-connect load cells and trim outputs for equal contribution
A summing box connects multiple load cells in parallel and uses trim resistors to balance each cell's contribution to the total signal.
A technician measures zero balance on a new load cell and finds it is -0.3 mV/V. This indicates:
Answer: A normal condition within typical ±1% rated output tolerance
Zero balance offsets of ±1% of rated output are standard and are corrected by the indicator's zero calibration function.
Which mechanical symptom most likely indicates worn or damaged check rods on a vehicle scale?
Answer: Lateral movement of the deck when a vehicle drives on at an angle
Check rods (or stay rods) prevent lateral and longitudinal deck movement; wear allows the deck to shift sideways under off-axis loading.
When using an ohmmeter to check a load cell, a technician measures 0 Ω between the signal+ and signal− terminals. This most likely indicates:
Answer: A short circuit within the load cell bridge
Signal terminals should show the bridge output resistance (typically 350 Ω or higher); 0 Ω indicates a short across the output arms of the bridge.
Electrostatic discharge (ESD) protection in a weighing instrument is most effectively achieved by:
Answer: Properly bonding the instrument chassis to earth ground
Bonding the chassis to earth ground provides a low-impedance path for static charges to dissipate safely before reaching sensitive electronics.
A flexure-type load cell is preferred over a bending beam type in applications requiring:
Answer: High side-load rejection and minimal off-center sensitivity
Flexure load cells use guided flexure elements that inherently reject side loads and horizontal forces, making them suitable for precision platform scales.
What effect does a broken solder joint on one arm of a Wheatstone bridge have on scale output?
Answer: Reduced but non-zero sensitivity and a large zero offset
An open arm in the bridge creates an unbalanced circuit that still produces some output, but with degraded sensitivity and a large offset error.
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