So little system impact it can run on just a whisper

Low pressure drop minimizes system impact, enabling flow measurement and control at near-atmospheric pressures, perfect for aerospace and environmental gas analysis applications. Reduced pressure drop also means more process fluids go into your process and not into your measurement devices.
Brochure Specs Manual


Making You Faster

  • Low pressure drop enables faster stabilization for leak testing applications.
  • All flow data visible on one screen (mass flow, volumetric flow, absolute pressure, temperature).
  • No warm-up required: ready to operate in one second.
  • 5-ms speed of response for meters, 50-100 ms for controllers.
  • Accessible PID control valve tuning for best speed and stability.
  • Control mass flow, volumetric flow or absolute pressure with one device.
  • Numerous user-selectable engineering units.
  • Includes COMPOSER™ gas composition firmware.
Alicat MW Whisper series mass flow meter

Alicat MW Whisper series mass flow meter, shown with optional color display

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MW Low Pressure Drop Flow Meters

Alicat MW Whisper series mass flow
  • Alicat MW-Series Part Numbers
Monitor both mass and volumetric flow rates with no influence on the process being measured. Low pressure drop makes even volumetric flow monitoring easy and accurate. Max range: 0-500 slpm.
MW Specs Go to Meter page.

MCW/MCRW Low Pressure Drop Flow Controllers

Alicat MCRW high-flow Whisper series mass flow controller
  • Alicat MCW-Series Part Numbers
Control flows at near-atmospheric inlet pressures or wherever system pressure cannot be lost. Max range: 0-500 slpm.
MCW Specs Go to Controller page.

MCDW/MCRDW Low Pressure Drop Bidirectional Flow Controllers

Alicat high-flow bidirectional mass flow controller with low pressure drop
  • Alicat MCDW-Series Part Numbers
Simulate breathing processes with bidirectional volumetric and mass flow control and minimal pressure drop. Max range: -500 to +500 slpm.
MCD standard Specs Go to MCD page.

MWB Low Pressure Drop Portable Flow Calibrators

Alicat portable mass flow calibrator with optional color display
  • Alicat MWB-Series Part Numbers
Verify the outputs of gas chromatographs and other gas analyzers with no impact on their measurement processes. Low pressure drop allows precision calibration of volumetric flow instruments such as ambient air sampling and monitoring systems. Max range: 0-500 slpm.
MWB Specs Go to Portables page.

Common Instrument Options

  • High-accuracy calibration, permits use of the meter as a secondary transfer standard.
  • Bidirectional flow calibration, enables full-scale readings in both flow directions.
  • Downstream valve, optimizes control in vacuum conditions or backpressure applications.
  • Integrated flow totalizer, provides cumulative readings of total quantity flowed over time.
  • CSA Class 1 Division 2 (ATEX Zone 2) Area Classification, permits operation in hazardous environments.
  • 9-pin or 15-pin D-sub connectors, configured to match any existing pinout.
  • Modbus-RTU, available over RS-232 or RS-485. PROFIBUS also available.
  • Backlit color display, shines in low lighting environments.

View other available instrument options here.


Download MW Meter SpecsMCW Controller SpecsMWB Portable Calibrator Specs


  • Standard accuracy (NIST-traceable): +/- (0.8% of the reading + 0.2% of the full-scale range)
  • Optional high-accuracy calibration: +/- (0.4% of the reading + 0.2% of the full-scale range)
  • Accuracy specs apply to preloaded and COMPOSER™ gas calibrations.

Speed of Response

  • Typical flow reading response time constant: 5 ms (may be up to 10 ms under very low flow conditions)
  • Standard control response time constant: 50 ms (MCW/MCDW series)
  • High-flow control response time constant: 100 ms (MCRW/MCRDW series)



  • Whisper meter and controller ranges: any full-scale range from 0-0.5 sccm to 0-500 slpm
  • Standard linear range: 0.5-100% of full scale, 200:1 turndown


  • Maximum line pressure: 50 psig
  • Pressure drop: 0.06-0.69 psi at full scale, depending upon flow range


  • Standard communications: RS-232 digital and 0-5 volt analog
  • Optional analog communications: 1-5v, 0-10v, 4-20 mA; secondary outputs also available
  • Optional communications protocols: RS-485, Modbus RTU (over RS-232 or RS-485), PROFIBUS
  • Standard connector: 8-pin mini-DIN
  • Optional connector: 9-pin or 15-pin D-sub connectors, configured to match any existing pinout


  • Simultaneous real-time readings of setpoint, mass flow, volumetric flow, absolute pressure and temperature
  • Standard display: 2.1″ monochrome LCD digital display with touch pad interface
  • Optional 2.1″ backlit color TFT digital display with touch pad interface


  • Limited lifetime warranty
  • Controller unaffected by bumps, humidity or changes in orientation

Gas Select™ 5.0 Gas List for Alicat Mass Flow Meters and Controllers

All Alicat Scientific mass flow meters and mass flow controllers come standard with NIST Ref Prop 9 gas properties data for up to 130 preloaded gas calibrations. Users may switch between selected gases on the fly without any need for recalibration of the mass flow meter or controller. All Gas Select™ calibrations retain the instrument's specified NIST-traceable calibration accuracy. (See individual specifications sheets for details.)
Pure GasesBioreactor Gas MixesPure Corrosives
• Acetylene (C2H2)
• Air
• Argon (Ar)
• i-Butane (i-C4H10)
• n-Butane (n-C4H10)
• Carbon dioxide (CO2)
• Carbon monoxide (CO)
• Deuterium (D2)
• Ethane (C2H6)
• Ethylene/Ethene (C2H4)
• Helium (He)
• Hydrogen (H2)
• Krypton (Kr)
• Methane (CH4)
• Neon (Ne)
• Nitrogen (N2)
• Nitrous Oxide (N2O)
• Oxygen (O2)
• Propane (C3H8)
• Sulfur Hexafluoride (SF6)
• Xenon (Xe)
• 5% CH4 95% CO2
• 10% CH4 90% CO2
• 15% CH4 85% CO2
• 20% CH4 80% CO2
• 25% CH4 75% CO2
• 30% CH4 70% CO2
• 35% CH4 65% CO2
• 40% CH4 60% CO2
• 45% CH4 55% CO2
• 50% CH4 50% CO2
• 55% CH4 45% CO2
• 60% CH4 40% CO2
• 65% CH4 35% CO2
• 70% CH4 30% CO2
• 75% CH4 25% CO2
• 80% CH4 20% CO2
• 85% CH4 15% CO2
• 90% CH4 10% CO2
• 95% CH4 5% CO2
*These gases require MS/MCS-Series instruments.
• Ammonia (NH3)
• Butylene (1-Butene)
• Cis-Butene (cis-2-Butene)
• Iso-Butene
• Trans-Butene
• Carbonyl Sulfide (COS)
• Chlorine (Cl2)
• Dimethylether (CH3OCH3)
• Hydrogen Sulfide (H2S)
• Nitrogen Trifluoride (NF3)
• Nitric Oxide (NO)
• Propylene (C3H6)
• Silane (SiH4)
• Sulfur Dioxide (SO2)
Breathing GasesFuel Gas MixesRefrigerants
• EAN-32 (32% O2+68% N2)
• EAN-36 (36% O2+64% N2)
• EAN-40 (40% O2+60% N2)
• EA-40 (40% O2+60% Air)
• EA-60 (60% O2+40% Air)
• EA-80 (80% O2+20% Air)
• Heliox-20 (20% O2+80% He)
• Heliox-21 (21% O2+79% He)
• Heliox-30 (30% O2+70% He)
• Heliox-40 (40% O2+60% He)
• Heliox-50 (50% O2+50% He)
• Heliox-60 (60% O2+40% He)
• Heliox-80 (80% O2+20% He)
• Heliox-99 (99% O2+1% He)
• Metabolic Exhalant (16% O2+78.04% N2+5% CO2+0.96% Ar)
Coal Gas 50% H2+35% CH4+10% CO+5% C2H4
Endothermic Gas 75% H2+25% N2
HHO 66.67% H2+33.33% O2
LPG HD-5 96.1% C3H8+1.5% C2H6+0.4% C3H6+1.9% n-C4H10
LPG HD-10 85% C3H8+10% C3H6+ 5% n-C4H10
Nat Gas 93% CH4+3% C2H6+1% C3H8+2% N2+1% CO2
Nat Gas 95% CH4+3% C2H6+1% N2+ 1% CO2
Nat Gas 95.2% CH4+2.5% C2H6+0.2% C3H8+0.1% C4H10+1.3% N2+0.7% CO2
Syn Gas 40% H2+29% CO+20% CO2+11% CH4
Syn Gas 64% H2+28% CO+1% CO2+7% CH4
Syn Gas 70% H2+4% CO+25% CO2+1% CH4
Syn Gas 83% H2+14% CO+3% CH4
*These gases require MS/MCS-Series instruments.
• R-11 Trichlorofluoromethane (CCl3F)
• R-14 Tetrafluoromethane (CF4)
• R-22 Difluoromonochloromethane (CHClF2)
• R-23 Trifluoromethane (CHF3)
• R-32 Difluoromethane (CH2F2)
• R-115 Chloropentafluoroethane (C2ClF5)
• R-116 Hexafluoroethane (C2F6)
• R-124 Chlorotetrafluoroethane (C2HClF4)
• R-125 Pentafluoroethane (C2HF5)
• R-134A Tetrafluoroethane (CH2FCF3)
• R-142B Chlorodifluoroethane (CH3CClF2)
• R-143A Trifluoroethane (C2H3F3)
• R-152A Difluoroethane (C2H4F2)
• RC-318 Octafluorocyclobutane (C4F8)
• R-404A (44% R-125+4% R-134A+52% R-143A)
• R-407C (22% R-32+25% R-125+52% R-134A)
• R-410A (50% R-32+50% R-125)
• R-507A (50% R-125+50% R-143A)
Chromatography GasesOxygen Concentrator Gas Mixes
• P-5 (5% CH4+95% Ar)
• P-10 (10% CH4+90% Ar)
• 89% O2+7% N2+4% Ar
• 93% O2+3% N2+4% Ar
• 95% O2+1% N2+4% Ar
Welding GasesStack/Flue Gas MixesLaser Gas Mixes
• C-2 (2% CO2+98% Ar)
• C-8 (8% CO2+92% Ar)
• C-10 (10% CO2+90% Ar)
• C-15 (15% CO2+85% Ar)
• C-20 (20% CO2+80% Ar)
• C-25 (25% CO2+75% Ar)
• C-50 (50% CO2+50% Ar)
• C-75 (75% CO2+25% Ar)
• He-25 (25% He+75% Ar)
• He-50 (50% He+50% Ar)
• He-75 (75% He+25% Ar)
• He-90 (90% He+10% Ar)
• A1025 (90% He+7.5% Ar+2.5% CO2)
• Stargon CS (90% Ar+8% CO2+2% O2)
• 2.5% O2+10.8% CO2+85.7% N2+1% Ar
• 2.9% O2+14% CO2+82.1% N2+1% Ar
• 3.7% O2+15% CO2+80.3% N2+1% Ar
• 7% O2+12% CO2+80% N2+1% Ar
• 10% O2+9.5% CO2+79.5% N2+1% Ar
• 13% O2+7% CO2+79% N2+1% Ar
• 4.5% CO2+13.5% N2+82% He
• 6% CO2+14% N2+80% He
• 7% CO2+14% N2+79% He
• 9% CO2+15% N2+76% He
• 9.4% CO2+19.25% N2+71.35% He
• 9% Ne+91% He

Ask Alicat: What Is Pressure Drop?

Pressure drop is the amount of line pressure that is permanently lost as gas passes through an instrument in a gas line. Alicat Scientific demonstrates the importance of pressure drop for gas flow processes and shows how you can greatly reduce pressure drop by using its Whisper Series of mass flow instruments.

Ask Alicat: How fast is an Alicat mass flow controller?

Flow stability and accuracy depend on fast control response, and Alicat is the fastest. This video demonstrates 0 to 100% setpoint changes with settling times of less than 30 ms and control T/C of only 7.4 ms.

Ask Alicat: What is the fastest way to validate flow rates?

Alicat Scientific’s rechargeable mass flow meters deliver laboratory-class accuracy in a handheld instrument that lasts 18 hours on a single charge.

The Fastest Flow Controller Company in the World

How can Alicat claim to be the fastest flow controller company in the world? This video introduces you to some of the many ways that Alicat mass flow and pressure instruments can make you more efficient, saving you time and money.

Ask Alicat: How tough is an Alicat flow meter? (Drop Test)

We drop an Alicat portable mass flow meter onto unforgiving concrete from increasing heights to test the toughness of this product. After each drop, we compare its measurement to the pre-test baseline.

Alicat Turndown Ratio for Mass Flow

Alicat demonstrates an incredible 5000:1 turndown ratio, commanding a 5 slpm (5000 sccm) mass flow controller to control down to 1 sccm!

Ask Alicat: How do you control flow in TWO directions?

Alicat Scientific introduces the world’s first bidirectional flow and pressure controller: the dual-valve MCD. Control mass flow, volumetric flow and pressure in both directions with stand-alone control and 30 on-board gas calibrations over a 200:1 turndown range. Or control pressure or flow into a closed process, and vent the volume with no need for additional bleed valves or continuous outgassing. The MCD is the single most versatile flow controller in the world.


Whisper low pressure drop mass flow meter

Alicat MW-Series “Whisper” low pressure drop mass flow meter, shown with optional color display

Alicat MCRW high-flow "Whisper" series mass flow controller, shown with downstream valve

Alicat MCRW high-flow “Whisper” series mass flow controller, shown with downstream valve

Alicat portable mass flow calibrator with optional backlit color display

Alicat Whisper-series portable flow calibrator, shown with optional backlit color display.

Alicat's new rechargeable portable mass flow meter

Alicat Whisper-series portable flow calibrator, shown with standard monochrome display.

In the Box

Compatible Accessories:

Calibration of an Air Sampling Canister

Rapidly calibrate across multiple ranges and gases without carrying a computer. NIST-traceable high-accuracy calibration makes your portable a transfer standard. “Whisper” low pressure drop enables non-intrusive volumetric flow calibration.
See the full app note here.

Calibration of an air sampling canister using an Alicat Whisper portable flow calibrator

Calibration of an air sampling canister using an Alicat Whisper portable flow calibrator

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.
See the full app note here.

Easy mass air flow leak testing setup, including a single Alicat "Whisper" mass flow controller, set up for absolute pressure control

Easy mass air flow leak testing setup, including a single Alicat “Whisper” mass flow controller, set up for absolute pressure control