Simplified Measurement Verification Practice Test

Zero drift is the change in the zero reading of an instrument over time, which creates a constant bias in all measurements. If the baseline or zero reference shifts, every measurement moves away from the true value, reducing accuracy even though the input hasn’t changed. This is different from random noise, which causes quick, non-persistent fluctuations around the current zero, and from span or gain drift, which changes the scale of the readings rather than just the baseline. It’s also not about how tightly repeated measurements cluster at high or full-scale values—that concerns precision at the upper end, not the zero baseline. In practice, monitoring zero stability and recalibrating helps keep measurements accurate as conditions vary.