Mass Flow Controllers & Meters


MCW – Whisper Series : Low Pressure Drop Gas Mass Flow Controller

Responsive gas flow control with minimal system impact


Order Directly from Alicat


Alicat “Whisper” Series mass flow controllers with low pressure drop are ideal for controlling mass and volumetric flow rates when there is little available system pressure. Low pressure drop minimizes system impact, enabling flow control at near-atmospheric pressures and shortening system response times. We’ll use your application parameters to customize your valve and PID tuning to ensure that it delivers fast and stable control while maintaining low pressure drop.

  • Versatile. Control pressure while monitoring flow rates, select another gas calibration on the fly or define your own gas composition with COMPOSER™.
  • Connected. Easy integration into your digital industrial network with EtherNet/IP, EtherCAT, DeviceNet, Profibus, Modbus (RTU and TCP/IP) or serial communications options.
  • Durable. Backed by annual recalibrations and our limited lifetime warranty, an Alicat instrument will keep your process running smoothly, even in challenging environments, for years to come.


  • Available ranges: max 0-1000 slpm, min 0-0.5 sccm/0-500 sμlm
  • Steady state control range: 0.01% – 100% of full scale.
  • Standard accuracy calibration, NIST-traceable: +/- (0.8% of the reading + 0.2% of the full-scale range)
  • Optional high-accuracy calibration, NIST-traceable: +/- (0.4% of the reading + 0.2% of the full-scale range)
  • Repeatability: 0.2% of the full-scale range
  • Typical control response time constant: 50-100 ms (as low as 25 ms with PID tuning)
  • No warm-up time required

Operating Conditions

  • Compatible gases: 98 pre-loaded selectable gas calibrations; additional mixtures definable with COMPOSER
  • Operating temperature: -10°C to +60°C
  • Max internal pressure (static): 45 psig (60 psia)
  • Proof pressure: 175 psig (190 psia)
  • STP/NTP: user-selectable (defaults to 25°C & 1 atm STP/0°C & 1 atm NTP)

In the box

Model Variations

  • Standard configuration, max 160 psia (MC)
  • High pressure, 160-320 psia (MCQ)

Valve Options 

Your mass flow controller may be customized with one of the following valving options to ensure optimal performance under your expected process conditions.

  • MCW – small proportional control valve for flow ranges of 2 slpm and below
  • MCPW – small proportional control valve with the largest orifice (not available for corrosive configurations)
  • MCHW – hammerhead configuration, which pairs two small valves working side-by-side as one valve
  • MCRW – nearly frictionless large Rolamite proportional valve for flow rates of 5 slpm and above

Build Options

  • Communications protocols (analog, RS-232, RS-485, DeviceNet, EtherCAT, EtherNet/IP, Modbus RTU or TCP/IP, PROFIBUS)
  • Displays (monochrome or color, integrated or panel-mount)
  • Process connections (NPT, SAE, AN, BSPP/G, welded compression or VCR/VCO fittings)
  • Elastomers (Viton, FFKM, EPDM, Silicone)

Performance Options

Alicat’s MCW series uses small proportional valves for control at lower flow rates and is suitable for use with non-corrosive gases.


Alicat’s MCPW series offers the largest orifice in a small valve format and is suitable for use with non-corrosive gases.


Alicat’s MCHW series pairs two small valves working side-by-side as one and is suitable for use with non-corrosive gases.


Alicat’s MCRW series uses nearly frictionless Rolamite valves and a variety of orifice patterns for control at higher flow rates and is suitable for use with non-corrosive gases.


Even Faster Leak Testing

For leak checking smaller test volumes, such as valves or sensors, a single MCW “Whisper” mass flow controller that is set to control for pressure will maintain a constant pressure at the device under test while providing accurate mass and volumetric flow readings in real time. Configured this way, the Whisper serves the functions of both a pressure controller and a mass flow meter in one device.

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