Control compressed gas precisely
It’s the smart approach to calibration

Ralston Instruments offers more ways to control compressed gas than anyone in the industry.

Pressure Control Illustration

Compressed Gas

Use onboard nitrogen or any compressed gas gas source

Reference Gauge Compatibility

Connect to standard digital or analog gauges using Ralston gauge adapters

Soft Seated Valves

Soft seated valves make filling and bleeding pressure very easy and controlled

Volume Control

Control pressure precisely using pressure balanced volume control (available on QTVC and NPAK models)

Controlling compressed gas for precise calibration at any pressure level


-30 in Hg to 0
(-584 mmHg to 0)


  • Vacuum gauge calibration

  • Absolute pressure measurement

Pressure Media:

  • Vacuum (supplied from vacuum pump)


Low Pressure

0 to 100 psi
(0 to 7 bar)


  • Calibrating pressure gauges

  • Pressure transmitter calibration

  • Airspeed indicator calibration

Pressure Media:

  • Compressed gas


Medium Pressure

100 psi to 300 psi
(7 bar to 20 bar)


  • Static pressure transmitter calibration

  • Pressure gauge calibration

  • Float piston gauges

Pressure Media:

  • Compressed gas


High Pressure

300 psi to 5,000 psi
(20 bar to 350 bar)


  • Safety relief valve testing

  • Pressure gauge calibration

  • Deadweight replacement

Pressure Media:

  • Compressed Gas


Using Volume Control to Optimize Pressure Calibration

Elements of Volume Control Illustration
Fine Adjust Piston
Fill Valve
Vent Valve
Balance Valve

Benefits of Volume Control VS Pressure Regulation

A traditional pressure regulator and needle valves work by filling and bleeding the pressure which wastes a great deal of compressed gas. Because pressure regulators are designed to work with flowing gas or liquid they work very poorly when there is no flow.

A compressed gas control device actually changes the volume of a closed system to control the pressure. This approach makes it more accurate and easier to use. The pressure balanced design of the QTVC and NPAK models provide higher precision due to smoother operation and larger piston diameter.

Fine Control Over Compressed Gas

Regardless of the process being controlled, Ralston Instruments makes a compressed gas control device to serve the purpose. Made in America using the highest grade parts, our manifolds are the most economical way of performing static pressure calibrations in the shop or in the field. Select a single manifold or opt for the convenience of a fully integrated calibration kit – either way, our units adapt to your needs.

See All Calibration Models

Precision and Stability at Any Pressure

For the ultimate in accuracy with a wide pressure range, Ralston Volume Controllers provide highly stable pressure control from vacuum to 3000 psi. Coupled with nitrogen or other compressed gas to control pressure, our Volume Controllers regulate pressure precisely without time consuming pumping. Ralston Volume Controllers are the next generation of calibration instruments.

See All Volume Controllers

Integrated Pressure Source and Volume Controller

When you need to perform pressure calibration in remote locations, a Ralston Intruments Nitropak is your best option. This fully integrated calibration kit contains everything you need — from a compressed gas cylinder, pressure regulator, hoses, adapters all contained in an extremely rugged carrying case with rigid foam that keeps instruments securely in place. Set up takes seconds and precise pressure control is easy to achieve despite difficult or remote working conditions.

See All Nitropak Options