Analog units: ±2.0% of full scale
Digital units: ±2.0% of reading, ±1 least significant digit
(Limited to accuracy of calibration standard)

Less than ±2.0% of full scale (24 hours)

The zero and span drift specifications assume that the analyzer is equilibrated, and is at constant temperature, with a properly maintained sensor. "Drift" is defined as an undesired change in output over a period of time, which change is unrelated to input, operating conditions, or load.