The Ashcroft AVC series is a precision mechanical pressure controller that generates and adjusts pneumatic pressure in closed systems with laboratory-grade resolution — without requiring a compressed gas cylinder, external pump, or electronic pressure controller. The operating principle is elegantly simple: a precision-machined piston inside a honed cylinder is advanced or retracted by a fine-thread leadscrew driven by the adjustment knob. Each rotation of the knob displaces the piston by a known distance; this displacement changes the volume of the closed gas space proportionally; and in a closed pneumatic system of fixed volume, Boyle's Law (P₁V₁ = P₂V₂) converts the volume change into a predictable, repeatable pressure change. There are no electronics to calibrate, no compressed gas bottles to replace, and no pumps that pulsate.

Why is the AVC series used in place of a deadweight tester?

Deadweight testers provide NIST-traceable pressure by loading calibrated weights on a piston of known area — they are the gold standard for pressure calibration but are heavy (a full weight set for 3,000 psi can weigh over 50 kg), not portable, and require a clean, vibration-free laboratory environment. The AVC provides a practical alternative for field calibration and test benches where portability and speed matter: it generates pressure from vacuum to 3,000 psi without weights, adjusts pressure continuously (not in discrete weight increments), and can be used in any orientation. For applications that do not require the ±0.015% of reading accuracy of a laboratory deadweight tester, the AVC's fine resolution (0.00025 psi on the AVC-1000) enables setting a test pressure with more than sufficient precision for calibrating industrial pressure switches, transmitters, and gauges. It is frequently used as the pressure source paired with a precision digital reference gauge to create a portable calibration station.

How does the integral balance valve work?

The balance valve connects the high-pressure side of the piston to the low-pressure (reference) side. Opening the balance valve equalizes pressure on both sides of the piston, removing the differential force that makes the adjustment knob hard to turn at high pressures. The operator opens the balance valve, adjusts the knob to the approximate position, closes the valve, and then makes the final fine adjustment — the balanced piston moves with fingertip effort regardless of system pressure. The same valve also functions as a safety relief: if the system pressure exceeds the set range, the balance valve opens automatically, venting excess pressure to the low-pressure side and preventing over-pressurization damage to the device under test.