| Clean, dry air | Manual hand pump with fine adjustment and volume control | Vacuum to approximately 40 bar (600 psi), depending on design | About 0.05% to 0.25% of reading or full scale for complete systems | Portable, self-contained, low operating cost, and clean for pneumatic instruments | Manual effort; pressure stability depends on operator technique and leakage control | Field calibration of pressure transmitters, switches, gauges, and low-to-medium pressure sensors |
| Clean, dry air | Pneumatic comparator using a regulated external air supply | Typically from low pressure to approximately 100 bar (1,500 psi) | Often about 0.025% to 0.1% of full scale when paired with a suitable reference | Fast pressure generation, good repeatability, and reduced operator effort | Requires a clean, dry, stable supply and suitable filtration | Workshop calibration, production-line testing, and repeated instrument verification |
| Clean, dry air | Motorized or electrically driven pneumatic pump | Commonly vacuum to 20–70 bar (300–1,000 psi), depending on pump configuration | About 0.01% to 0.05% of full scale with a high-quality reference sensor | Rapid generation, automated test sequences, and reduced fatigue during multiple-point calibration | Needs electrical power; pump noise, heat, and pulsation may require filtering or stabilization | Automated test benches, high-throughput maintenance, and multi-point calibration routines |
| Nitrogen or other dry inert gas | Gas regulator, precision pressure controller, or gas booster | From low pressure to several hundred bar; equipment-specific | Approximately 0.01% to 0.1% of full scale, depending on the controller and reference | Very dry, clean, and chemically inert; suitable where moisture or oxygen is undesirable | Gas cylinders require handling, storage, and ventilation controls; operating cost is higher than ambient air | Moisture-sensitive devices, oxygen-sensitive processes, and high-accuracy laboratory calibration |
| Hydraulic oil or other compatible liquid | Hand-operated or motorized hydraulic pump with fine adjustment | Typically 0 to 700 bar (0 to 10,000 psi); higher ranges are possible with specialized equipment | About 0.01% to 0.05% of full scale for complete calibration systems | Liquid has low compressibility, enabling high pressure and stable readings | Potential contamination, cleanup requirements, temperature effects, and incompatibility with some sensors | High-pressure gauges, transmitters, safety valves, and industrial hydraulic equipment |
| Distilled or deionized water | Water-operated hand pump or hydraulic pressure controller | Usually low to medium hydraulic pressure; commonly up to approximately 700 bar | Often about 0.02% to 0.1% of full scale, depending on system design | Low contamination risk for compatible equipment and easier disposal than oil | Can promote corrosion, may freeze, and is unsuitable for devices that must remain completely dry | Water-compatible pressure instruments and applications requiring a low-residue medium |
| Air or inert gas | Pressure controller with closed-loop electronic regulation | Commonly vacuum to 20–100 bar; range depends on the control module | Approximately 0.005% to 0.025% of full scale in laboratory-grade systems | Excellent repeatability, programmable setpoints, automatic stabilization, and data logging | Higher acquisition cost; requires power, configuration, and periodic verification | Calibration laboratories, automated production testing, and digitally documented procedures |