Series 810 Instruction Manual
Chapter 1 Introduction
Figure 1-4. Sensor Temperature Distribution
The RTD coils are legs of a bridge circuit with an output voltage in
direct proportion to the difference in the coils' resistance; the result is
the temperature difference (OT), Figure 1-4. Two other parameters,
heat input (H) and coefficient of specific heat (Cp) are both constant.
The resulting output is nearly linear over the transducer's normal
operating range (Figure 1-5).
Figure 1-5. Linear Range of the Transducer's Output Signal
For mass flow
controllers
, once the gas flows through the
monitoring section, it is then controlled by the built-in servo-control
valve. All models of the Mass-Trak utilize Sierra's proprietary high-
efficiency Fast-Trak Electromagnetic Valve. The normally closed
Fast-Trak valve is similar to an on/off solenoid valve, except that the
current to the valve coil, and hence the magnetic field, is modulated
so that the ferromagnetic valve armature, or valve plug, assumes the
exact height above the valve's orifice required to maintain the
valve's command flow. The result is nearly infinite resolution.
IM-81
1-5
