Primary piston flow meter calibration

Primary piston meter calibration involves verifying the accuracy of the timing mechanism and the piston displacement volume against traceable reference standards. Although these instruments derive their measurement from primary dimensional standards, all instruments drift over time and require periodic recalibration to confirm their continued accuracy. UKAS calibration provides a traceable certificate that can be used to support occupational hygiene sampling programmes and regulatory monitoring.

While primary piston meters are reference-grade instruments derived from dimensional standards, their performance can be affected by wear, contamination, temperature changes and mechanical factors over time. UKAS calibration confirms the instrument’s current accuracy and provides documented evidence of traceability, which is required for most occupational hygiene and environmental monitoring programmes, including HSE COSHH assessments and asbestos monitoring.

Yes, primary piston meters such as the MesaLabs Bios Defender (DryCal) are widely used to calibrate lower-accuracy flow meters including rotameters and personal sampling pumps. For this use to be valid, the piston meter itself must hold a current UKAS calibration certificate, establishing the traceability of all downstream calibrations. Without a valid UKAS certificate for the DryCal, the traceability chain is broken.

Most occupational hygiene and environmental monitoring standards recommend annual calibration, with some protocols requiring pre- and post-campaign calibration for critical sampling programmes. The Health and Safety Executive (HSE) guidance on air sampling and the MDHS series of methods specify that sampling equipment must be calibrated at appropriate intervals. Annual UKAS calibration is the standard approach for maintaining compliance.

A well-maintained primary piston meter in calibration is typically accurate to within ±0.5–1% of reading. UKAS calibration determines the actual deviation from the true flow rate at each calibrated point and states the measurement uncertainty. This information is provided on the calibration certificate and should be used when assessing whether the instrument meets the accuracy requirements of your sampling programme.