Digital Valve Division

The Digital Valve is a unique Mass Flow Control System (MFCS) designed for fast and simultaneous metering and control of fluids. The MFCS consists of a Digital Valve (DV) and a Digital Valve Control Unit (DVCU).

A Digital Valve (DV) is an array of parallel arranged flow restrictors - typically sonic nozzles or orifices - each of which operates in an on/off state (flow, no-flow).  With this arrangement the flow rate can be changed by adjusting the combination of opened / closed elements. Each active element allows fluid to flow between the common inlet and outlet chambers (plenums).  Since the pressure drop between the plenums is the same for all elements, an active element will flow at a rate proportional to the restrictor area.  This results in flow to be "digitized" since each flow restrictor area is a precise fraction of the total flow.

The Digital Valve Control Unit (DVCU) calculates and controls mass flow of a known gas through a Digital Valve (DV). The mass flow calculation is based on sonic flow, using valve inlet pressure and valve inlet temperature.  Mass flow control is achieved by selecting an appropriate combination of valve elements to produce the specified flow rate.  The calculation and control cycle is adjustable, with a minimum cycle time of 100 ms.  An electronics package provides the interface between the sensors, Digital Valve and control computer.  The control program runs on a standard Windows based computer.  The interface between the computer and the electronics packages is via an RS-485 link or an Ethernet link.

Specifications:

  • Speed of response: 100 - 250 ms (depending on appl.)
  • Range / Resolution: 4095 : 1 standard
  • Overshoot / Hysteresis: None
  • Fail safe: Open or closed
  • Accuracy: +/- 0.5% standard
  • Repeatability: +/- 0.25%
  • Body Material: 316L SS
  • Valve Seat Material: Fluid compatible material
  • Pressure Capacity: 5000 psi


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