Intek 111D - Manual (Page 4)

- 2 -
MAN114 REV C.wpd
1.2 DESCRIPTION OF OPERATION
Rheotherm flow meters are available with various nonintrusive and intrusive transducer designs, but
they all use the same thermal sensing technique. Two temperature sensors are used — one is in thermal
equilibrium with the fluid and provides a fluid temperature reference, while the second temperature
sensor is located near a heater so that its temperature is slightly above that of the fluid. In tube style
transducers, the temperature sensors and heater are attached to the outside of the flow tube, whereas the
probe transducers have the sensors and heater located in the probe(s) that are inserted into the stream.
The amount of heat removed from the heated sensor by the stream is related to fluid velocity. Hence,
the measured temperature differential between the reference sensor and heated sensor is a function of
flow rate. Intek, Inc. is licensed to use this patented and trademarked flow measurement technique.
Nonintrusive tube transducer Example of Example of
probe probe with
with NPT fitting flange for mounting
1.3 PRECAUTIONS
1. Use proper input power — Check the label on the electronics for the input power
requirements.
2. Use reasonable care in handling the transducer. Do not try to disassemble the transducers;
there are no removable parts.
Tube (TU, TUL, TUS, etc.) — excessive twisting or bending can damage the sensor. The flow
tubes are thin-walled tubing.
Probes (NPT/2I, NPT/I, BF/2I, BF/I, etc.) — take care not to bend the probes or damage the
tips. Do not try to remove or turn the conduit junction box.
3. All tube sensors under ¼” should be supported by the sensor shell, not the tube stubs. Tube
sensors using junction boxes or sensors without junction boxes can be supported with the pipe
clamps or some other appropriate means. Tube sensors with junction box can be supported
using the brackets machined into the junction box.