The High-Precision Positive Displacement Flow Meter NKGF Series is a compact positive displacement (PD) flow meter designed for accurate measurement of low and ultra-low liquid flow.

The High-Precision Micro Gear Flow Meter uses precision-machined elliptical gears installed inside a precision measuring chamber. As liquid passes through the measuring chamber, the pressure difference between the inlet and outlet causes the gears to rotate. The rotating gears repeatedly displace a defined volume of liquid, allowing the flow volume to be determined from gear rotation.

The flow meter provides a minimum detectable flow rate of 0.5 mL/min, with specified accuracy options of ±0.5% FS or ±0.2% FS, depending on the selected model and configuration.

A white PTFE (Polytetrafluoroethylene) material configuration is available for applications requiring a PTFE material option.

The flow meter is intended primarily for clean liquid measurement and is suitable for a range of low-flow applications including chemical dosing, precision dispensing, lubrication, hydraulic oil monitoring, ink and coating systems, and OEM fluid control equipment.

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Key Features

• Positive displacement volumetric measurement principle
• Minimum detectable flow rate of 0.5 mL/min
• Accuracy options of ±0.5% FS or ±0.2% FS
• Designed for low and ultra-low liquid flow measurement
• Suitable for liquid viscosities of 2–200 mPa·s
• Higher-viscosity applications available upon request
• Precision-machined elliptical gear measuring mechanism
• White PTFE material configuration available
• Pulse or 4–20 mA output for applicable electronic versions
• 24 VDC power supply for applicable remote and intelligent display models
• High-temperature configuration up to 200°C with Heat Sink
• Optional insulated jacket
• Ex ia IIC T5 explosion-proof configuration available for applicable models

Note: Performance, pressure, temperature, output, material, and explosion-proof specifications depend on the selected model and configuration. Please confirm the final specification before ordering.

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Technical Specifications

Measurement Performance

Important Specification Note

The 0.5 mL/min value represents the specified minimum detectable flow rate. It should not be interpreted as the complete flow measurement range.

The available accuracy is specified as ±0.5% FS or ±0.2% FS, depending on the applicable model and configuration. Actual measurement performance should be evaluated under the specified operating conditions.

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Fluid Specifications

The flow meter is designed for clean liquids.

The applicable viscosity and temperature limits depend on the selected product configuration and the actual operating conditions.

For liquids outside the standard viscosity range, the application should be evaluated before selection.

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Operating Pressure

The following pressure specifications are retained from the supplied product data:

Important Note for PTFE Configuration

The pressure values above correspond to the listed Cast Iron, Stainless Steel, and Cast Steel configurations.

They should not be automatically applied to the white PTFE configuration.

For the white PTFE version, the applicable maximum pressure must be confirmed according to the specific model, construction, operating temperature, and actual application.

This distinction is important because material selection and operating temperature can affect the allowable pressure of the complete flow meter assembly.

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Material Configuration

The flow meter is available in different material configurations according to the selected product version.

Available configurations in the supplied product specification include:

• White PTFE
• Cast Iron
• Stainless Steel
• Cast Steel

White PTFE Configuration

The white PTFE configuration is designed for applications requiring a PTFE material option.

PTFE is widely used where chemical compatibility and non-metallic material construction are important considerations.

However, material compatibility should always be evaluated against the actual liquid, temperature, pressure, and wetted components before ordering.

The use of PTFE does not by itself define the pressure or temperature rating of the complete flow meter. These values must be confirmed for the specific configuration.

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Output and Power Supply

Applicable remote and intelligent display versions support electrical signal output.

These electrical specifications apply to the corresponding electronic versions and should not be assumed to apply to every mechanical configuration.

Pulse Output

Pulse output can be used by an external control or acquisition system for flow monitoring and calculation.

4–20 mA Output

The 4–20 mA output can be integrated with compatible industrial control, monitoring, and data acquisition systems.

The wiring and electrical connection should follow the specifications of the selected model.

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Explosion-Proof Configuration

An explosion-proof configuration is available with the following specified rating:

Ex ia IIC T5

This specification applies to the applicable product configuration.

The actual explosion-proof applicability must be confirmed according to the selected model, certification documentation, hazardous-area classification, and installation requirements.

Important: The product page should not describe the complete product series as ATEX, IECEx, FM, CSA, or otherwise certified unless the corresponding certification has been obtained for the specific model.

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High-Temperature Configuration

The standard fluid temperature specification is:

-20°C to +80°C

A high-temperature configuration is available:

Up to 200°C with Heat Sink

The 200°C value applies to the applicable high-temperature configuration and should not be interpreted as the standard operating temperature of every model.

For high-temperature applications, the actual:

• Fluid temperature
• Ambient temperature
• Operating pressure
• Material configuration
• Heat-sink configuration

should be confirmed before product selection.

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Operating Principle

Positive Displacement Measurement

The High-Precision Micro Gear Flow Meter uses a pair of precision-machined elliptical gears inside a measuring chamber.

When liquid enters the chamber, the pressure difference between the inlet and outlet causes the gears to rotate.

During rotation, the gears repeatedly trap and displace a defined volume of liquid.

The basic measurement relationship is:

Measured Volume = Number of Gear Rotations × Calibrated Displacement Volume

By detecting the rotation of the gears, the flow meter can determine the amount of liquid passing through the measuring chamber.

This is the fundamental operating principle of a positive displacement flow meter.

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Why Use a Positive Displacement Micro Gear Flow Meter?

Direct Volumetric Measurement

The flow meter measures liquid through repeated displacement of a defined volume rather than relying solely on fluid velocity.

This makes the positive displacement principle suitable for applications requiring volumetric measurement of relatively small liquid flows.

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Suitable for Low-Flow Applications

The specified minimum detectable flow rate is:

0.5 mL/min

This makes the product suitable for applications where low liquid flow measurement is required.

The actual applicable flow range should be confirmed according to the selected model because 0.5 mL/min is the minimum detectable flow specification, not a complete model flow range.

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Performance Across Different Viscosities

The specified standard viscosity range is:

2–200 mPa·s

Positive displacement flow meters can be suitable for a range of liquid viscosities because measurement is based on volumetric displacement.

However, actual measurement performance is influenced by operating conditions, including:

• Flow rate
• Fluid viscosity
• Pressure
• Temperature
• Internal clearances
• Calibration conditions

Therefore, the flow meter should be selected according to the actual fluid and operating conditions rather than assuming that viscosity has no effect on measurement performance.

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Suitable Media

The flow meter is designed for clean liquids.

Depending on material compatibility and the selected configuration, typical applications may include:

• Hydraulic oil
• Lubricating oil
• Compatible fuels
• Process chemicals
• Ink
• Coatings
• Resins
• Adhesives
• Other compatible clean liquids

The above list describes potential application media rather than a universal compatibility statement.

For a specific liquid, the compatibility of the complete wetted construction should be confirmed before ordering.

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Media Not Recommended

Liquids Containing Solid Particles

The flow meter is designed for clean liquids and is not recommended for liquids containing solid particles.

Solid particles may enter the precision measuring chamber and interfere with gear rotation, potentially affecting measurement performance or causing mechanical damage.

Where required, suitable filtration should be considered based on the actual application.

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Gas Measurement

The product is designed for liquid measurement.

The standard micro gear flow meter is not intended for gas measurement.

Gas applications require a flow meter specifically designed for compressible fluids.

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High-Viscosity Liquid Measurement

The specified viscosity range is:

2–200 mPa·s

Higher-viscosity applications can be evaluated upon request.

For a positive displacement flow meter, fluid viscosity can affect internal leakage within the measuring chamber. Under suitable operating conditions, increased viscosity can reduce leakage, but this does not mean that measurement accuracy is independent of viscosity.

For this reason, customers should provide the actual viscosity and flow range when requesting model selection.

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Product Configuration Options

The High-Precision Micro Gear Flow Meter can be configured according to application requirements.

Accuracy

• ±0.5% FS
• ±0.2% FS

Material

• White PTFE
• Cast Iron
• Stainless Steel
• Cast Steel

Output

Applicable electronic versions:

• Pulse
• 4–20 mA

Power Supply

Applicable electronic versions:

• 24 VDC

Temperature

• Standard: -20°C to +80°C
• High-temperature configuration: up to 200°C with Heat Sink

Explosion-Proof Option

• Ex ia IIC T5

Optional Configuration

• Insulated Jacket

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Typical Applications

The High-Precision Micro Gear Flow Meter is designed for low-flow liquid measurement applications where positive displacement measurement is appropriate.

Chemical Dosing

For monitoring low-volume flow in chemical dosing and process equipment, subject to material compatibility.

Laboratory Equipment

For clean-liquid measurement in laboratory and analytical equipment.

Precision Dispensing

For applications requiring controlled and repeatable delivery of small liquid volumes.

Lubrication Systems

For monitoring compatible lubricating liquids in precision lubrication equipment.

Hydraulic Oil Monitoring

For monitoring compatible hydraulic oils and other clean oil-based liquids.

Fuel Measurement

For compatible liquid fuels within the specified operating conditions and material compatibility limits.

Ink and Coating Systems

For compatible clean inks, coatings, and similar process liquids.

Resin and Adhesive Metering

For compatible resins, adhesives, and other liquid materials within the specified viscosity and temperature range.

OEM Fluid Control Equipment

The compact gear-based measuring structure and optional electronic outputs make the flow meter suitable for integration into OEM equipment.

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Selection Guide

To select the appropriate micro gear flow meter, customers should provide the following information:

Providing complete operating conditions helps ensure that the selected model is suitable for the actual application.

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Technical Specification Summary

Specification note: The values above represent the available specifications supplied for the product. Not all specifications necessarily apply to every configuration. Final pressure, temperature, accuracy, output, material, and explosion-proof specifications should be confirmed against the selected model and applicable product documentation.

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Frequently Asked Questions

What is the minimum detectable flow rate?

The specified minimum detectable flow rate is:

0.5 mL/min.

This value should not be interpreted as the complete flow range. The applicable flow range depends on the specific model.

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What accuracy is available?

The specified accuracy options are:

• ±0.5% FS
• ±0.2% FS

The applicable accuracy depends on the selected model and configuration. Actual performance should be evaluated under the specified operating conditions.

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What liquids can the flow meter measure?

The product is designed for clean liquid measurement.

The standard viscosity range is:

2–200 mPa·s

Higher-viscosity applications can be evaluated upon request.

The actual liquid must also be compatible with the wetted materials of the selected configuration.

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Can the flow meter measure high-viscosity liquids?

Yes, applications with higher viscosity can be evaluated.

The standard specified viscosity range is 2–200 mPa·s, and higher-viscosity applications are available upon request.

Actual performance depends on the flow rate, pressure, temperature, viscosity, and selected model.

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Can the flow meter measure gas?

No. The standard product is designed for liquid measurement and is not intended for gas measurement.

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Can it measure liquids containing particles?

It is designed for clean liquids and is not recommended for liquids containing solid particles because particles may interfere with the precision gear mechanism.

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What is the standard operating temperature?

The specified standard fluid temperature range is:

-20°C to +80°C.

A high-temperature configuration is available for temperatures up to:

200°C with Heat Sink.

The 200°C specification applies to the applicable high-temperature configuration.

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What is the maximum operating pressure?

The supplied specifications are:

• Cast Iron: 1.6 MPa
• Stainless Steel: 1.6 MPa
• Cast Steel: 2.5 MPa or 6.4 MPa

These values should not be automatically applied to the white PTFE configuration.

The pressure rating of the PTFE version must be confirmed according to the specific model and construction.

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Is a white PTFE version available?

Yes.

A white PTFE configuration is available.

For specific applications, the compatibility of PTFE and all other wetted components with the actual liquid should be confirmed before ordering.

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Does the flow meter support 4–20 mA output?

Yes, applicable remote and intelligent display versions support 4–20 mA output.

The specified power supply for these versions is 24 VDC.

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Is an explosion-proof version available?

An Ex ia IIC T5 configuration is specified as available for applicable models.

The exact certification and installation suitability should be confirmed against the product’s certification documentation and the requirements of the intended hazardous area.

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Important Technical Notes

For accurate product selection, the following points should be considered:

1. 0.5 mL/min is the specified minimum detectable flow rate, not the complete flow range.
2. ±0.2% FS is an available accuracy specification and should be confirmed for the selected model.
3. The 1.6 MPa, 2.5 MPa, and 6.4 MPa pressure values correspond to the specified metal material configurations and should not be applied to PTFE without confirmation.
4. The 200°C temperature specification applies to the applicable high-temperature configuration with Heat Sink.
5. 24 VDC and 4–20 mA/Pulse output apply to the corresponding electronic versions.
6. The standard product is intended for clean liquids, not gas or particle-containing liquids.
7. Ex ia IIC T5 should be confirmed against the actual certification documentation for the selected model.
8. Actual measurement performance depends on the complete operating conditions and selected configuration.

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Conclusion

The High-Precision Micro Gear Flow Meter uses a positive displacement measuring principle and precision elliptical gears to measure the volume of clean liquids passing through the measuring chamber.

With a specified minimum detectable flow rate of 0.5 mL/min and available accuracy specifications of ±0.5% FS or ±0.2% FS, the meter is designed for low-flow liquid measurement applications.

The product supports a standard fluid viscosity range of 2–200 mPa·s, with higher-viscosity applications available upon request. The standard fluid temperature range is -20°C to +80°C, while an applicable high-temperature configuration can support temperatures up to 200°C with Heat Sink.

A white PTFE configuration is available, providing a PTFE material option for applications where this material is required. Other specified material configurations include Cast Iron, Stainless Steel, and Cast Steel, with their respective pressure ratings defined separately.

Applicable electronic versions support 24 VDC, Pulse, and 4–20 mA configurations, while an Ex ia IIC T5 explosion-proof option is available for applicable models.

The flow meter is suitable for applications such as chemical dosing, precision dispensing, laboratory equipment, lubrication systems, hydraulic oil monitoring, fuel measurement, ink and coating systems, resin and adhesive metering, and OEM fluid control equipment, provided that the actual fluid and operating conditions are compatible with the selected configuration.

For model selection, please provide the actual flow range, liquid viscosity, temperature, operating pressure, medium, required accuracy, material, and output requirements.