Analog & Digital Scale Technology Flashcards

When performing a shift (off-center load) test on a platform scale, test weights are placed:

Answer: At multiple off-center positions across the platform surface

A shift test places a standard test load at multiple off-center positions sequentially to verify the scale reads the same regardless of load placement.

The excitation voltage supplied to a strain gauge load cell by the digital indicator is typically:

Answer: 5 to 15 V DC

Digital indicators supply 5–15 V DC excitation to load cells; this powers the Wheatstone bridge and determines the full-scale output signal.

What does 'NTEP Certificate of Conformance' signify for a commercial scale?

Answer: The scale type has been evaluated and found to meet NIST Handbook 44 requirements

An NTEP Certificate of Conformance (CC) means the scale design has been tested and approved as conforming to NIST Handbook 44 for legal-for-trade use in the US.

Which component in an analog spring scale directly converts the applied force into pointer deflection?

Answer: Helical or flat return spring

The helical or flat spring is the primary sensing element that deflects proportionally to the applied weight, driving the pointer across the graduated dial.

A legal-for-trade digital scale must have its calibration parameters protected against unauthorized changes by:

Answer: A calibration security seal or software security access event log

NIST Handbook 44 requires that calibration parameters be secured by a physical seal or an audit trail event log so any changes are detectable.

In a multi-load-cell platform scale, junction boxes are used primarily to:

Answer: Sum and trim individual load cell signals before sending a single output to the indicator

Junction boxes parallel-connect multiple load cells and include trimming potentiometers to equalize individual cell outputs, providing a single summed signal to the indicator.

What effect does a decrease in ambient temperature have on the output of a standard (uncompensated) strain gauge load cell?

Answer: Zero shift and span change due to changes in gauge resistance and elastic modulus

Temperature changes alter both the resistance of strain gauges and the elastic modulus of the flexure, causing zero shift and span error in uncompensated load cells.