Calibration Techniques & Procedures Flashcards

A pressure transmitter calibrated at sea level is relocated to an installation at 5,000 feet elevation. For a gauge pressure transmitter, this change will:

Answer: Shift the zero reading because gauge pressure references local atmospheric pressure

Gauge pressure is measured relative to local atmospheric pressure; at higher elevation, lower atmospheric pressure causes the zero point to shift, requiring re-zeroing at the new location.

During calibration, a technician applies 50% of input range and observes a reading 2% of full scale higher than expected consistently across three trials. This error is best classified as:

Answer: Systematic error (bias) at mid-scale

A consistent, repeatable offset at the same input point across multiple trials indicates a systematic bias rather than random scatter or hysteresis.

The primary reason calibration procedures specify a stabilization period after changing the input to the unit under test is to:

Answer: Allow transient responses to decay so the instrument reaches steady-state before reading

Instruments have response time constants; reading before steady-state is reached introduces a dynamic error that is not representative of the instrument's static accuracy.

When calibrating a torque wrench, the applied reference torque is usually generated by hanging calibrated weights at a known distance from the drive axis. The formula used is:

Answer: T = F × d (where F = weight force, d = moment arm length)

Torque equals force multiplied by the perpendicular distance (moment arm) from the axis of rotation; T = F × d is the fundamental torque equation.

A calibration technician must calibrate a volumetric flask. The gravimetric method determines volume by:

Answer: Weighing a known mass of water delivered by the flask and dividing by water density at that temperature

The gravimetric method uses the relationship V = m / ρ, where mass is measured precisely and water density at the measured temperature is obtained from tables to calculate true volume.

Which of the following actions would invalidate an instrument's calibration status and require recalibration before further use?

Answer: Dropping the instrument or subjecting it to mechanical shock

Mechanical shock can alter the physical characteristics of sensors, springs, or electronic components, introducing unknown errors that cannot be corrected without recalibration.

In a calibration procedure that requires 'overlapping range points,' the purpose is to:

Answer: Verify consistency at points that fall within the uncertainty intervals of adjacent calibration points

Overlapping points detect non-linearities or inconsistencies between segments of the calibration curve that would be missed if each point were measured only once in a strict sequence.