Omega FMA1800A, Руководство пользователя, Страница: 13 / 36

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5. OPERATING INSTRUCTIONS
5.1 Preparation and Warm Up
It is assumed that the Mass Flow Meter has been correctly installed and thor-
oughly leak tested as described in section 2. Make sure the flow source is OFF.
Apply power to the unit by plugging the power supply line into the DC power
jack (or 9-pin 'D' connector) on the side of the meter. Allow the Mass Flow
Meter to warm-up for a minimum of 15 minutes.
SUPPLYING DC POWER TO THE POWER JACK AND THE “D” CONNECTOR AT
THE SAME TIME WILL DAMAGE THE METER. DC POWER JACK POLARITY
IS CENTER POSITIVE.
During initial powering of the FMA1700A/1800A transducer, the flow output sig-
nal will be indicating a higher than usual output. This is indication that the
FMA1700A/1800A transducer has not yet attained it's minimum operating tem-
perature. This condition will automatically cancel within a few minutes and the
transducer should eventually zero. If after the 15 minutes warm-up period, the
display still indicates a reading of less than ± 3.0 % of F.S., readjust the ZERO
potentiometer [R34] through the access hole. Before zero adjustment it is good
practice to temporarily disconnect the gas source, to ensure that no see page or
leak occurs in to the meter.
5.2 Flow Signal Output Readings
Initiate a controlled gas flow after warm up. The flow signal output can be viewed
either on the LCD display, remote panel meter, digital multimeter, or other display
device.
If an LCD display has been supplied with the FMA1700A/1800A, the observed
reading is in direct engineering units (0 to 100% indication is optional).
Analog output flow signals of 0 to 5 VDC and 4 to 20 mA are attained at the appro-
priate pins of the 9-pin “D” connector (see Figure 2.a) on the side of the
FMA1700A/1800A transducer.
Meter signal output is linearly proportional to the mass molecular flow rate of the
gas being metered. By default calibration is done against 0 to 5 VDC output sig-
nal. If 4-20 mA output signal is used for flow indication on the FMA1700A/1800A,
which was calibrated against 0 to 5 VDC, the total uncertainty of the reading may
be in the range of +2.5% of full scale. Optional calibration for 4-20 mA output sig-
nal is available upon request at time of order. The full scale range and gas for
which your meter has been calibrated are shown on the flow transducers front
label.
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ADJUSTING ZERO READING MORE THAN ± 3.0% F.S. FROM THE FACTORY
SETTINGS MAY AFFECT DEVICE CALIBRATION ACCURACY. IF SUCH
ADJUSTMENT IS REQUIRED IT IS RECOMMENDED TO PERFORM METER
RECALIBRATION TO PRESERVE DEVICE ACCURACY.
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