Pressure calibrators

Pressure calibrators are portable or bench instruments dedicated to the periodic calibration of pressure gauges, pressure transmitters, pressure switches, safety switches and other pressure measuring devices. They combine a controlled pressure source (manual pump, semi-automatic, or automatic with a compressor and regulator) and a high-accuracy reference transducer that measures the pressure actually generated, to be compared with the reading of the device under calibration. They are used in accredited calibration laboratories, in test centers, in companies with in-house calibration requirements, in specialized workshops and in sector technical services.

Portable calibrators

Portable calibrators combine in a single instrument: a manual or motorized pressure generation pump (typical ranges from −1 bar vacuum to 700 bar pressure); a fine regulator for stabilizing the pressure value; a high-accuracy reference transducer (typical class 0.025–0.1% F.S.); a digital display with comparison functions and percentage error calculation; an auxiliary input for the device under calibration (connection for reading the output signal of the gauge or transmitter); automatic certificate functions that generate formal reports. They are compact and battery powered, ideal for on-site service where taking the instruments back to the laboratory is impractical.

Deadweight testers

Deadweight pressure testers are the absolute primary reference for calibration: a piston of calibrated area in a cylinder loaded with certified masses generates a pressure that can be calculated exactly as F/A. They are instruments of the highest accuracy (classes 0.008–0.025% of the generated value), used in legal metrology laboratories and in high-class ISO 17025 laboratories. The pressure is set by selecting the appropriate masses from the kit supplied. They cover ranges from a few mbar to 1000 bar and beyond, with specific models for hydraulic pressure (with oil) and pneumatic pressure (with air or nitrogen).

Automatic bench calibrators

Automatic bench calibrators use internal compressors and electronic regulators to generate and hold the required pressure automatically, with dedicated software that runs standardized calibration procedures (5–10 points across the range, an ascending and descending cycle, statistics, report printing). They are used in calibration laboratories with high workloads, where productivity is essential. Typical accuracies are 0.01–0.05% F.S., with extended ranges (vacuum, pneumatic up to 100 bar, hydraulic up to 1000–2000 bar). Integration with document management software guarantees full traceability and the generation of ISO 17025 certificates.

Applications

Typical use is in: ISO 17025 accredited calibration laboratories (providing services to external customers); in-house industrial metrology departments (for the periodic calibration of plant gauges); maintenance of pressure equipment (boilers, exchangers, tanks – calibration of safety valves and of mandatory gauges); the pharmaceutical industry (calibration of gauges on CIP/SIP lines and in autoclaves); oil & gas (calibration of process instrumentation on site); aerospace (testing of pneumatic and hydraulic components); R&D in the instrumentation sector.

Reference standards

The calibration of pressure transducers follows ISO/IEC 17025 for laboratories, EN 837-1 for Bourdon gauges and OIML R109 for legal metrology. Typical procedures involve: conditioning the device; calibration at 5 points distributed across the range with ascending and descending cycles; calculation of linearity, hysteresis and overall error; issue of a certificate with the expanded uncertainty (k = 2, 95% confidence). Traceability to national primary standards (in Italy INRIM and Accredia) must be documented.

Selection criteria

The choice of calibrator depends on: the pressure range required (vacuum, low, medium or high pressure); the accuracy required (the class of the calibrator must be at least 4× better than the class of the instruments to be calibrated); the method of generation (manual for portability, automatic for productivity); the working fluid (air or gas for pneumatics, oil for hydraulics); the software for managing and generating ISO 17025 certificates; integration with company databases and LIMS; and the support and periodic calibration service for the calibrator itself.