Parker | Porter

Frequently Asked Questions

Parker mass flow products reflect over three decades of experience in the design and manufacture of precision instruments for the measurement and control of gas flow. They incorporate design principles that are simple and straightforward, yet flexible enough to operate under a wide variety of process parameters. Parker's Mass Flow Controllers are accurate, reliable, cost effective solutions to your mass flow application needs.


01. What are the advantages of a digital MFM/MFC when compared to an analog MFM/MFC?

Digital Series 500 MFM's & Series 600 MFC's offer ± 0.8% of reading plus ± 0.2% full scale accuracy & linearity with ± 0.2% of rate repeatability. A majority of the analog Series 100 MFM's or Series 200 MFC's have ±1% full scale accuracy & linearity with ± 0.2% full scale repeatability.

Digital MFM's/MFC's allow a user to store in memory as many as eight (8) calibration curves. If using our Series 100 MFM's or Series 200 MFC's, the correction for any additional gases must be done manually or programmed in the secondary electronics.

Digital control circuitry reduces 'dead time' when ramping from zero flow conditions. LED operation indicators confirm proper operation of the digital control circuitry.

Digital MFM's/MFC's have many parameter settings for signal processing, controlling, etc.

02. What output signals are available?

The digital series MFM's/MFC's offer Modbus, 0-5 Vdc, 0-10 Vdc & 4-20 mAdc (sourcing) output signals. The analog series MFM's/MFC's offer 0-5 Vdc, 0-10 Vdc, 1-5 Vdc, 4-20 mAdc (sourcing) & 4-20 mAdc (sinking) output signals.

03. How do I build a complete model?

First, determine whether a MFM or MFC is required for the application. Define the gas, flow range & desired type of output signal, allowing the basic model to be selected. To complete the model number, define the type of PC board electrical connector (if not already defined by the type of output signal), elastomer material, process fitting size & type & any special features.

04. What are your lead times?

Our 'typical' lead time is 3-4 weeks after receipt of order. Often times, this can be improved. Tell us your required in-house date & we will do whatever we can to accommodate your request.

05. What information, in addition to the model number, is required to place an order?

Define the gas type, operating temperature, upstream (supply) pressure, downstream (outlet) pressure (downstream pressure required for MFC's only), calibration standard & are any additional accessories (e.g. interconnecting cable assemblies, secondary electronics, etc.) required.

06. What is a 'calibration standard'?

Calibration standard is the standard reference temperature used when expressing a gas volume or a volumetric flow rate & must be defined because gas volume varies with the temperature & pressure of the gas. The calibration standard temperature should not be confused with the process operating temperature.

Common calibration standards are 0°C (32°F), 20°C (68°F), 21.1°C (70°F) & 25°C (77°F). Lesser known calibration standards are 15°C (59°F) & 15.6°C (60°F).

The standard pressure is 14.7 PSIA & does not require definition. Although less common standard pressure values exist (e.g. 100 kPa, 101.325 kPa, 14.503 PSIA, 14.696 PSIA, 14.73 PSIA), 14.7 PSIA is employed as the standard pressure at Parker Instrument.

07. What accessories (e.g. power supply, cables, secondary electronics package, etc.) are required & available?

A basic MFM/MFC system consists of a MFM/MFC, power supply, digital indicator/totalizer/batch counter, a setpoint signal source (required for MFC's only) & an interconnecting cable assembly. Multi-channel secondary electronics packages incorporating a power supply, a digital indicator & command potentiometers (setpoint signal sources) are available as an option to supplying the required components individually. Other more sophisticated secondary electronics packages (e.g. programmable logic controllers, etc.) may also be coupled with a MFM/MFC. Various types & lengths of interconnecting cable assemblies are available.

08. Is my MFM/MFC capable of operating on multiple gases?

Yes, however there are limitations. Sizing a MFM involves the thermodynamic properties of the process gas. To correct from the gas for which the unit was originally calibrated to another gas involves a simple mathematical correction. This is the only sizing required for a MFM. Using our Digital Series 500 MFM's or Series 600 MFC's allows a user to store in memory as many as eight (8) calibration curves. If using our Series 100 MFM's or Series 200 MFC's, the correction for the second gas must be done manually or programmed in the secondary electronics.

Sizing a MFC is more involved & involves two (2) sizings. The first sizing involves the flow meter portion of the MFC as explained above for a MFM. The second sizing is for the control valve, which contains a fixed orifice, an orifice of a fixed size. The orifice size is calculated based on gas density, flow range, inlet pressure & outlet pressure. Changing any one of these four parameters will affect your orifice size, & possibly, affect the control valve's operation. Without actually trying the second gas at the desired operating parameters, it is often difficult to predict how an MFC will control a second gas.

09. Are your MFM's/MFC's compatible with customer-supplied secondary electronics?

Compare the MFM/MFC specifications with those of the secondary electronics to determine compatibility. If using an MFC, confirm the power supply's current rating is sufficient to power the MFC. The most commonly encountered problem is not connecting the commons. The circuit common & valve common should be connected at the common of the power supply.

10. What is the lowest flow range available in an MFC at an elevated pressure?

The gas type, inlet pressure & outlet pressure all determine the lowest obtainable flow range. It is best to contact the factory to have the application sized.

01. What is a Rotameter?

A Variable Area Flow Meter is a flow measuring device that operates on the principle of allowing fluid flow to pass around a float housed in a tapered tube. As flow force increases (normally from higher flow rates), the float moves up the tapered tube to allow for more flow area around the float. The measured flow rate then corresponds to the location of the float within the tube.

02. What are the correction formulas for changes in Temperature, Pressure, and or Specific Gravity in a Variable Area Flow Meter? Are these formula found on line in the Web site?

See attached Formula factor sheets (not on line at this time)

03. What is meant by +/- 5% Full Scale Accuracy (FSA) ?

The full scale of a flow Meter would be the maximum flow range indicated on the scale of a specific tube and float combination.

Example: A flow meter with an advertized accuracy of +/- 5% FSA and a maximum flow range of 1000 sccm Air would have a accuracy of +/- 50 sccm Air at any point of flow between 100% to 10% of the maximum flow.

04. What are your lead times?

Our 'typical' lead time is 3-4 weeks after receipt of order. Often times, this can be improved. Tell us your required in-house date & we will do whatever we can to accommodate your request.

05. Why don't we stock preassembled flow meters for immediate shipment?

High number of parts variations economically prohibits the stocking of completed flow meters.

01. Do we supply a self relieving regulator?

No, Parker mechanical regulators are Non-Relieving.

02. Do we offer pressure gauges for our regulators?


03. Can these regulators be used in vacuum applications?

These regulators do not control properly when used in a vacuum application.

04. Can end fittings be supplied in sizes larger than 1/8" NPT or compression fittings?

No. There is not enough surface area available for NPT ports that are larger than 1/8" NPT.

01. Customers have asked if we can supply the VCD-1000 with elastomers other than Viton or Fairprene?

No. The valve seat is available in Viton only.

02. Why do needle valves develop leaks at shut-off and will not close completely no matter how hard the knob is tightened down?

Excessive force used to achieve positive shut-off can deform or score the sealing surface in the valve. Parker Standard Cartridge Valves are available with the exclusive Torque Guard Stop Mechanism. The Torque Guard eliminates stem damage caused by over tightening of the valve at shut-off.

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