Sierra C100L-L-DD-LE-5-OV1-SV1-PV1C-V1-S1, Инструкция по эксплуатации

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Sierra Instruction Manual MaxTrak 180
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Figure 2. Flow Measuring Principle
Figure 3. Sensor Temperature Distribution
Figures 2 and 3 show the mass flow through the sensor tube as inversely proportional to the temperature difference of
the coils. The 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 (∆T). Two other parameters, heat input (H) and coefficient of
specific heat (Cp) are both constant. Through careful design and attention to these parameters, this output signal is
made linear over the transducer’s normal operating range (Figure 4). As a result, the measured flow through the
sensor tube is directly proportional to the gas flow in the main body.
Figure 4. Linear Range of the Transducer's Output Signal
In the MaxTrak mass flow controllers, the gas which flows through the monitoring section is precisely regulated
by the built-in electro-magnetic valve. The normally closed 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 (set point). The result is excellent resolution.