• Flow Rate of ±0.1 to 40ft/sec in most applications
  • Any pipe ID from 1/2 to 180in
  • ±2% of scale accuracy
    • Requires solids or bubbles of at least 100 microns
    • 75ppm concentration
  • ±0.1%, Linearity ±0.5% of full scale repeatability
  • Large, backlit LCD display
  • 12-Digit totalizer
  • Reverse flow measurement
  • Isolated 4-20mA (1000 ohm)
  • 2 programmable control relays (upgradeable to 6)
  • Automatic sensitivity adjustment
  • Built-in 5-key calibrator
  • 2 million point data logger optional
    • USB output to flash memory

What's in the Box

  • SE4-A clamp-on, single head ultrasonic sensor
  • Shielded coaxial pair sensor cable
  • Silicone sensor compound kit
  • Sensor mounting clamp for 0.6 to 32in OD pipes
  • Installation and operation manual
  • NIST certificate


The Greyline Instruments DFM 5.1 Doppler flow meter is a simple, non-contact meter designed for applications that would defeat regular contacting flow meters. Because the sensor is mounted on the outside of the pipe, it is unaffected by abrasives or harsh chemicals making it ideal for wastewater, slurries, sludge, chemicals, viscous liquids and abrasives. There is no obstruction to flow and no pressure drop. The DFM 5.1 is recommended for full pipes and any fluid that contains solids or bubbles.

The Greyline DFM 5.1 works with PVC, carbon steel, stainless steel, cast iron, fiberglass, and lined pipes-- essentially any pipe material that conducts ultrasound. The non-intrusive, clamp-on ultrasonic sensor fits any pipe with an inside diameter from 1/2 to 180 inches. Installation is easy and doesn't require the system be shut down. No contact is made with the moving fluid and no pipe cutting or drilling is required. There is no fouling or scale build-up on the sensor.

The DFM 5.1 Doppler flow meter includes an isolated 4-20mA to transmit flow to remote displays, recorders or controllers. The two programmable relays (upgradeable to six) can be used for flow control, pump protection or flow proportionate pulse. Calibration is easy with the built-in 5-key calibrator. Display and totalize flow in your choice of engineering units (gallons, liters etc.). The standard sensor is rated non-incendive for Class I, Division 2 hazardous locations and the DFM 5.1 can be equipped with optional Intrinsic Safety Barriers for sensor installation in Class I, Division I hazardous locations. A built-in 2 million point Data Logger with USB output to Flash Drives is also available.


This product can be used in the following applications:

Here's how some of our customers use this product...

Construction Site De-watering

The Background: Our customer is a large construction company currently working on a project in which groundwater has seeped into areas that have been excavated. The customer needs to monitor the amount of water they pump out of those areas.

The Problem: The water has a lot of suspended solids. Also, the customer does not need a long term solution, only something until the seepage is mitigated.

The Solution: Since power is available on site, the water contains sufficient suspended solids, and there was straight, full pipe available for installation, we recommended the Greyline Instruments DFM 5.1 doppler meter with onboard data-logger.

Measuring Spent Grain Flow

The Background: Our customer is a brewery that wants to monitor the flow of their spent grain discharge line.

The Problem: The spent grain line is water with high solid content making it a prime candidate for a Doppler style ultrasonic flow meter with clamp-on technology, though the customer is accustomed to measuring in mass units.

The Solution: We recommended the Greyline Instruments DFM 5.1 Doppler Flow Meter paired with a Define Instruments LD-PRC Panel Meter. Though the DFM 5.1 will only provide velocity measurement, by assuming a constant density of the spent grain, the 4 and 20mA scaling points of the LC-PRC can easily be manipulated to output a pound per minute mass flow rate.

In this particular application, the DFM 5.1 Doppler flow meter will output a 4-20mA signal that equates to 0-100 GPM (gallons per minute). The customer has provided a spent grain density of 7.753 lb/gal (pounds per gallon) so the 20mA programming in the LD-PRC is set to 775.3 lb/min (100 gal/min x 7.753 lb/gal = 775.3 lb/min).

Mining Slurry

The Background: Our customer is a mining company that needs to measure the amount of ore slurry transported through an 8-inch pipeline.

The Problem: The ore slurry contains about 75% solids which would quickly destroy any inline flow meter.

The Solution: We recommended the Greyline Instruments DFM 5.1 flow meter, a clamp-on ultrasonic flow meter that has no parts which obstruct the flow. The reliable Doppler technology has been proven to work very well even on extremely noisy, high solid content, lines.