Setra System Model 470 - Manual (Page 32)

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7.4 Span Calibration
To perform the span calibration on the 470, it is necessary to apply both the zero and the full
scale pressures, as described in the following procedure. This procedure can be aborted at any
point by setting the program enable switch to “OFF” and transmitting C, to execute the CLEAR
function.
1. Use the CONVERT function (see Section 4.2) so that the 470 reports data in units of
pressure in response to an interrogation. (i.e., the transducer should not be reporting in
units of altitude.)
2. Place the transducer and the pressure standard in a stable temperature environment for
at least two hours before calibration.
3. Set the program enable switch to “ON” (Section 7.2).
4. Transmit SF, for SETUP FULL SCALE. The 470 responds “APPLY”, followed by the
pressure required for zero calibration, and repeats this response until Step 7 is reached.
5. If the 470 responds “NO CAL”, the program enable switch in Step 3 is not set. Transmit
C, for CLEAR and restart the procedure.
6. Apply the indicated zero pressure from a high accuracy standard.
7. When the pressure is stable, transmit S, for SETUP.
8. The 470 takes data and responds “APPLY”, followed by the pressure required for full
scale calibration, and repeats this response until Step 10 is reached.
9. Apply the indicated full scale pressure from a high accuracy standard.
10. When the pressure is stable, transmit S, for SETUP.
11. The transducer takes data, adjusts its zero and span calibrations. If there is a large
difference between the current data and the previous calibration, the transducer reports
“UNABLE”. If this occurs, first set the program enable switch to “OFF”, and transmit C,
for CLEAR. Next, verify that the correct pressure is applied and that the calibration
standard is of sufficient accuracy. If the problem persists, contact Setra for assistance.
12. The 470 responds “PROTEC”. Set the program enable switch to “OFF”
(Section 7.2). Transmit C, for CLEAR to resume normal operation.