Fox Thermal FT3 - Page 17

Welcome
Thank you for purchasing the model FT3 thermal gas mass ow meter from Fox Thermal. The FT3 is
one of the most technically advanced ow meters in the world. Extensive engineering eort has been
invested to deliver advanced features, accurate measurement performance and outstanding reliability.
This instruction manual contains the electrical and mechanical installation instructions as well as
details for programming, maintaining and troubleshooting the meter. This manual is divided into the
following sections: Introduction, Installation, Wiring, Operation, Communications,
Data Logger, Maintenance, Appendix, Denitions, and Index.
Theory of Operation
The model FT3 is an innovative thermal mass gas ow meter and temperature transmitter. It is
microprocessor-based and eld programmable. The FT3 thermal sensor operates on the law that
gases absorb heat. A heated sensor placed in an air or gas stream transfers heat in proportion
to the stream’s mass velocity. There are two sensor elements. One sensor element detects the
gas temperature and a second element is maintained at a constant temperature above the gas
temperature. The energy transferred from the heated element is proportional to the mass ow
velocity. The FT3 ow meter maintains accurate ow measurement over a large temperature and
pressure range.
Mass Flow
The model FT3 measures mass ow; an advantage over other ow meters which measure volumetric
ow rate. Volumetric ow is incomplete because temperature and pressure are unknown and must be
measured separately. For example, the mass ow of a gas depends on its temperature and pressure.
As temperature and pressure changes, the gas volume changes but not its mass. Therefore a device
measuring mass ow is independent of temperature and pressure changes. The model FT3 provides
a direct measurement of gas ow in mass units (kg/hr, lb/hr), standard units (SCFM, SLPM) or normal
units (NM3/hr, NLPM) with no additional temperature or pressure measurements required.
Calibration Validation
Fox Thermal has developed a method to validate the calibration of the ow meter in the eld. This
method is called Calibration Validation and it is made up of two distinct tests: CAL-V™ and Zero CAL-
CHECK™. The goal of Calibration Validation is to provide operators with the ability to verify that the
meter is capturing accurate data at scheduled recalibration times - or at any time - instead of sending
the meter back to the factory for recalibration.
By performing CAL-V™ in the eld, operators can verify that the meter is running accurately by testing
the functionality of the sensor and its associated signal processing circuitry. This test can be done
in the pipe and in normal processing conditions. The second test, Zero CAL-CHECK™, ensures the
eectiveness and sensibility of the sensor at a "no ow" condition.
Flow Calibration
Every Fox Thermal ow meter is set to the customer's conguration at the factory using an App ID
which is generated by the on-line congurator. The App ID species the gas type, ow range, serial
communication and other settings in the meter. If these settings match the nal customer application,
Model FT3
Introduction | 17
Introduction