The reliability of a leak test depends largely on the measuring instrument. The wrong range or low resolution can hide a small but significant pressure drop.
Measurement range
The instrument must safely cover the test pressure without operating continuously near the limit of its scale.
Resolution
Adequate resolution is required to check for small changes. A gauge that is too "coarse" may show stable pressure while a small change is occurring.
Accuracy
The accuracy of the instrument must be suitable for the test's acceptance criteria.
Calibration
The instrument must be within its valid calibration or verification period, depending on the facility's procedure.
Digital or analog
Both types can be suitable, provided they have the correct range, accuracy, and documented status.
