Omega 3200ST - Manual (Page 5)

M-4271/0707, pg. 5 of 26
sensor design. This proven design minimizes zero drift while maintaining
fast response and linear outputs with virtually no maintenance.
The FMA 3200/3400 Series
utilizes thermal flow sensing
technology. A portion of the
gas flowing through the unit is
redirected into a small sensor
tube. This tube has two coils
on the outside. The first coil
introduces a small amount of
heat into the gas stream. As
the gas passes through the
tube heat is transferred from
one coil to the other. The flow
rate is proportional to the
amount of heat transfer. Smart
electronics analyze the amount
of temperature change in the
second coil and provide a
linearized analog output. A patented system insures that the zero remains
stable and the sensor is extremely repeatable.
Flow in the FMA 3200/3400 Series is controlled by a proportional solenoid
valve with active servo electronics. The flow measurement signal is
analyzed by micro-processor controlled electronics and compared to a set-
point. Adjustments are then made to the valve in order to achieve the
required flow rate. The set point can be either externally input via a 0-
5VDC signal or in the case of the FMA 3400/3400ST Series it can be input
manually on the unit.
The output of the thermal mass flow sensor is directly related to the
specific heat characteristic of the gas being measured. A sensor is
calibrated for one gas but may be used with other gases by applying a
correction factor to the output. The calibration gas for each specific flow
controller is detailed on the product label.
B. Installation
Caution: Do not exceed the pressure, temperature or power
operating ranges detailed in the SPECIFICATIONS section of this
manual. Omega Engineering shall not be liable for any damage
or injury caused by incorrect operation of their products.
1. General Considerations
It is recommended that a safety shut-off valve be installed upstream
(before) of the controller.
All wetted parts should be checked for compatibility with the gas to be
used. If there are any incompatibilities eg. highly corrosive gas, then the