Since the supply air at the same time the test medium is more or less all testers respond to variations in pressure in the compressed air supply. This can for example be caused by large pneumatic cylinders are moved during the test phase. This can lead to larger scatter of test results.
May also prevent dirt, moisture or oil get into the test circuit. Where this can not be guaranteed, must be given to appropriate countermeasures.
Need to eliminate all these influences some rules:
Contamination can also come from the specimen. Should this danger exist, must also be created here by appropriate counter-measures (test air filter, exhausting box etc.) remedy.