Pressure Gauge Calibration

Harwood maintains a pressure standards laboratory with both primary and secondary standards for pressure gauge calibration services to 200,000 PSIG. Instruments are calibrated against either Harwood’s controlled clearance free piston gauges (Primary Standard) or Manganin® cell (Secondary Standard).


We also maintain a secondary standard for calibrating dynamic pressure gauges with an upsurging pressure of up to 150,000 psi.

Primary Standard – Controlled Clearance Deadweight Testers

Manganin Cell Pressure Gauge Calibration Harwood uses it’s own DWT-1000 controlled clearance free piston gauge for most calibrations. For low pressure ranges we also maintain two DWT-100s. The uncertainty of the primary measurement is ±0.02% of the reading (±40 psi at 200,000 psi).


Masses are checked triennially against the Harwood mass standards that are themselves re-certified every 4 years by Rice Lake Weighing Systems. The pistons are re-certified by a qualified meteorology laboratory whose standards are traceable to NIST.

Secondary Pressure Standard – Manganin® Cell

The total uncertainty of the Secondary Standard is ±100 PSIG. Harwood Manganin® cells are manufactured with carefully temperature-seasoned manganin wire and are pressure-seasoned to 300,000 psi. The cells have an active pressure-measuring coil with a resistance of 120 Ω ± 0.1 Ω. The remainder of the full bridge circuit is made up of precision wire wound ± 0.01% resistors. The pressure sensitivity of the wire is 1.65 x 10-7 ohms per ohm per psi.

Dynamic Gauge Calibrations

Harwood’s positive step pressure generator was designed to accurately calibrate dynamic gauges used in high pressure applications and is NIST traceable. Pressure ranges from 0-5,000 psi to 0-150,000 psi, with a surge time of approximately 0.2 milliseconds. The accuracy of this secondary standard device is ± 0.4 % of full scale.


For a quick quote or additional information on our pressure calibration services and capabilities, please contact Harwood Engineering Company directly.