Chapter 3 Operation
Series 810 Instruction Manual
below).
Note: If no setpoint command is present on a
controller when powered-up and the valve is not switched
off, the valve may drift wide open.
(The valve will open
momentarily when power is first applied).
2.
Apply power to your Mass-Trak using Sierra's power supply or your
own input power. When power is first applied, the output signal will
remain at a high level until the sensor reaches its normal operating
temperature range. This requires approximately 20 seconds, after which
time (assuming no gas flow is present) the signal and display will drop
to 0 VDC (or 4 mA). Allow at least 15 minutes of additional warm-up
time before performing any other performance checks or adjustments.
3.
Perform an initial zero output check (required for first-time start-ups
only). Make certain there is no gas flowing through the instrument.
Confirm that the display reads zero + 1.5% of full-scale and that the
output signal is less than + 0.075 VDC or + 0.24 mA (this is maximum
allowable within the accuracy specification of the transducer). If the
reading exceeds these limits, you may adjust the zero potentiometer
(located on the front panel—see Figure 1-1 in Chapter 1). Turning the
potentiometer screw clockwise increases the zero.
4.
Open the gas supply. Mass-Trak will begin monitoring the gas mass
flow rate
5.
Adjust the controller set point to the desired flow rate. The effective
control range of the unit is 10% to 100% of the calibrated full scale flow
range. Below 2%, the control valve will automatically shut off the flow
unless this function is disabled (see below).
Mass Flow Controller Features
Setpoint Adjustment
The setpoint input signal is a direct linear representation of 0-100% of the
mass flow full-scale value. A 0 VDC (or 4 mA) set point will regulate the
flow to 0% and a 5.00 VDC (20 mA) set point will adjust the flow to 100%
of the instrument's calibrated range.
The setpoint signal may be applied externally or internally. If you wish to
use the internal setpoint potentiometer, it may be accessed through the front
panel. Turning the potentiometer clockwise increases the setpoint. Either
0-5 VDC (0-10 VDC optional) or 4-20 mA external setpoint commands are
available through the D-connector. See Appendix C for wiring details.
When the command (setpoint) signal is applied, the flow controller will
respond to changes in the setpoint within six seconds to ±2% of full scale of
the selected flow rate.
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IM-81
