Brooks Instrument SLA5840 - Manual (Page 22)

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Brooks ® Model SLA5840
Section 3 Operation Installation and Operation Manual
X-PR-SLA5800-RT-eng
Part Number: 541B120AAG
August, 2009
E. Mode Select Pin
Connector Pin 13, on the15 pin D-Connector allows selection of one of ten
calibrations stored in the device. This pin is designed to accept pull-down
resistors referenced to signal common (Pin 10).
Table 3-1 shows typical resistor values required for selecting calibrations 1
through 10. Note, these resistor values should be within ± 1% tolerance.
The default condition is with no resistor connected which activates
Calibration #1.
When the calibration select pin changes state, the device performs any
required processing to change the calibration, then returns to normal
operation. If the device determines that the selected calibration is not valid,
(where applicable) the valve is driven to the closed state and the flow
signal is set to zero. Typical time required to change calibrations is
approximately 1.0 second.
NOTE: It is recommended to change calibration curve selection during no-flow
conditions.
F. Zeroing the MFC (Self-zero)
It may be desirable to re-zero the flow sensor if it is operated at its
temperature extremes or if it is positioned in an attitude other than that
specified on the customer order.
Note: Before zeroing the instrument, zero pressure differential MUST be established
across the device. If there is pressure across the instrument during the zero process,
any detected flow through the sensor will be misinterpreted as the zero flow reading.
This will result in calibration inaccuracy during normal operation.
Once zero differential pressure is established and verified, press the recessed,
momentary push-button (self-zero button) located on the side of the device
(See Figure 3-1) to start the self-zero function. The zeroing process requires
approximately 10 mseconds.
Once zero differential pressure is established and verified, press the
recessed, momentary push-button (Self-zero button) located on the side of
the device (See Fig. 3-1) to start the Self-zero function.
The zero process requires approximately 200 msec. During this time, the
device will set its output signal to 0.0 Vdc.