Ashcroft® precision-pressure volume controllers provide a quick-and-easy method for precisely setting a pressure in a closed pneumatic system. They are ideal for use with Ashcroft® Test Gauges for the calibration of other pressure-measurement and control devices.
The AVC unit consists of a volume chamber with an internal piston assembly. The piston seals across the diameter of the chamber. Once the AVC unit is connected to pneumatic system, the volume of the chamber becomes part of the volume of system. The pressure-adjust knob at the front of the unit repositions the piston within the chamber through interaction with a precision-machined lead screw. Piston movement within the chamber increases or decreases the volume of the system, depending on the direction of movement. In a closed system where gas cannot leak out upon compression or be drawn in upon expansion, this volume change results in a change in the internal pressure. Increasing the volume by moving the piston toward the front of the AVC unit will decrease the pressure. Conversely, decreasing the volume by moving the piston toward the rear of the unit will increase the pressure. The pressure change generated by a given amount of piston travel is proportional to the change in volume as compared to the total system volume.
AVC units are available for pressures up to 3,000 psi. The AVC-1000 can be used to set pressures from vacuum through 1,000 psi while the AVC-3000 can be used for pressures from vacuum through 3,000 psi.
An integral balance valve provides a means for equalizing pressure on both sides of the piston prior to making the final adjustments when setting the pressure. This minimizes the resistance encountered when repositioning the piston and assures ease of pressure setting, even at 3,000 psi. The balance valve also serves as a pressure-relief valve, assuring that the differential pressure across the piston does not reach unsafe levels.
AVC units can also be used without a compressed air source for the generation of moderate levels of positive pressure and vacuum. The high resolution of the AVC, combined with the ability to generate pressure and vacuum, make it an ideal tool for low-pressure (below 1 psi) calibration and test as well as higher pressure calibration and test activities.
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