CST CST Environmental Factors & Scale Performance 2 — Questions and Answers
Question 1: How does floor vibration from nearby machinery affect a platform scale's weight reading?
- It has no effect because modern digital filters eliminate all vibration
- It causes fluctuating weight readings that prevent the indicator from settling on a stable value (Correct answer)
- It permanently overloads and damages the load cells over time
- It only affects analog pointer scales, not digital indicators
Correct answer: It causes fluctuating weight readings that prevent the indicator from settling on a stable value
Floor vibration introduces dynamic forces on the load cell that cause the weight display to fluctuate continuously, preventing the indicator from achieving a stable, accurate reading.
Question 2: What device is used to isolate a floor scale from building vibration?
- A surge protector connected to the indicator power supply
- Vibration isolation pads or anti-vibration mounts placed under the scale feet (Correct answer)
- A Faraday cage installed around the load cell junction box
- A temperature controller mounted in the indicator enclosure
Correct answer: Vibration isolation pads or anti-vibration mounts placed under the scale feet
Anti-vibration isolation pads or mounts absorb and dampen mechanical vibrations from the floor, preventing them from transferring through the scale structure to the load cells.
Question 3: What is the purpose of the 'digital filter' or 'vibration filter' setting in a scale indicator?
- To filter electrical noise from the AC power supply line only
- To average multiple weight readings over a time period to reduce vibration-induced display fluctuation (Correct answer)
- To block unauthorized access to calibration menu settings
- To filter and format the data output sent to a connected printer
Correct answer: To average multiple weight readings over a time period to reduce vibration-induced display fluctuation
A digital filter averages multiple weight readings over a selectable time period, smoothing out vibration-induced fluctuations to provide a stable displayed weight reading.
Question 4: What mechanical feature protects load cells from permanent damage caused by sudden shock loading or overload impacts?
- The tare function, which zeros out shock forces
- Mechanical overload stops or bumpers that limit platform travel and deflection (Correct answer)
- The vibration filter setting in the scale indicator
- A fuse in the load cell excitation circuit
Correct answer: Mechanical overload stops or bumpers that limit platform travel and deflection
Mechanical overload stops physically limit how far the scale platform can deflect under load, preventing the load cells from experiencing forces beyond their safe overload rating.
Question 5: What maintenance procedure most effectively minimizes vibration-related inaccuracy in a floor scale installation?
- Setting the vibration filter to its maximum value permanently
- Periodically checking and tightening all mounting hardware, check rods, and leveling feet (Correct answer)
- Replacing all load cells on an annual preventive maintenance schedule
- Reducing the scale's rated capacity to lower the required division size
Correct answer: Periodically checking and tightening all mounting hardware, check rods, and leveling feet
Loose mounting hardware and leveling feet allow the scale platform to shift and rock under load, introducing mechanical movement noise that mimics vibration and produces inaccurate readings.
Question 6: Which NTEP certificate of conformance requirement indicates that a scale type has been tested and approved for use in dynamic weighing environments?
- Class I laboratory balance approval only
- Specific NTEP CoC listing approving the model for the intended dynamic or in-motion weighing application (Correct answer)
- Any NTEP approval covers both static and dynamic use automatically
- Class II precious metals scale approval
Correct answer: Specific NTEP CoC listing approving the model for the intended dynamic or in-motion weighing application
NTEP Certificates of Conformance are application-specific; a scale intended for dynamic or in-motion weighing must have an NTEP CoC that specifically covers that use, as static approval does not transfer.
CST CST Environmental Factors & Scale Performance 2
How does floor vibration from nearby machinery affect a platform scale's weight reading?