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Model: 600-9

Thermal Instrument was a pioneer of in-line flow meters. The unique design means the flow and temperature sensor are protected from passing fluids at all times. 

How do our Flow Meters Work?

Our In-line Thermal Mass Flow Meter Model 600-9 employs a unique design where the RTD sensors are mounted to the outer circumference of a pipe or tube in order to keep the sensors from coming into contact with the fluid passing through the instrument. 

This unique design allows for a fully unobstructed flow path and negligible pressure drop to your process application.


Our flow measurement instruments use two RTD sensors: one is self-heated and measures the flow and the other one measures the media temperature. The temperature sensor measures the heat of the media passing by and instantly corrects for changes in temperature. It then sets the temperature of the flow sensor to a precise temperature above that of the passing media.

Meter Accuracy

The accuracy of the flow measurement is based on the fact that all media conduct heats off the sensor in direct proportion to the mass flow rate. The higher the velocity in flow, the more heat is conducted away and therefore creating a repeatable relationship. Accurate flow readings can be measured on a process line as small as 1/16″ (1.59mm) in diameter; there’s no limit on maximum size.

There are two components that make up a Thermal Instrument inline mass flow meter: a flow element with a bridge controller and a signal transmitter. We offer our transmitter in both an integral and remote mount configuration allowing for a variety of installation options. Operational Flow display, Totalized Flow, Pulse Output, and Temperature outputs are available options. Our unique in-line design of our thermal mass flow meters offers no obstruction to the actual flow path allowing for excellent flow profiles and in turn, accurate and repeatable results.

Process Connection & Material Options

Spools are available with flanged, threaded, sanitary, VCR, VCO, Swagelok® or other constructions suitable to your system. Our Thermal Mass Flow Meters are manufactured using 316 SS as a standard, but corrosion resistant materials such as Hastelloy C, Monel, Inconel, Tantalum, and Carpenter 20 are also available.  In addition, our Thermal Mass Flow Meters are available in a variety of protective coatings including Carbide, Fluorocarbon, Teflon, and Sulfinert.

Sanitary & Ultrapure Options for Gas and Liquid Flow Measurement

These Thermal Instrument inline models are constructed of 316L, low sulfur stainless steel down to 10-15 RA finish and offer “CIP/SIP” clean-in-place design.  These models provide sanitary measurement options for our clients in the Food & Beverage, Pharmaceutical, and Semi-conductor industries to name a few. We offer a variety of cleaning options with avaliable certificates if necessary. They are available with our standard Tri-Clamp process connection, but also can be manufactured with VCR, VCO, or even tube end construction to meet a variety of process connection configurations. They also provide highly reliable service in flow switch applications with field adjustable Form C relay switch points.

These units are available with both integral and remote transmitter styles for outputting flow rates and temperature. 

Dimensional Drawing

Inline Flow Meter Specification Chart

Inline Flow Meter Ultra-High Purity (UHP) Sizing Chart

Inline Flow Meter Gas Sizing Chart

Inline Flow Meter Liquid Sizing Chart

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