Setra System Model 470 - Manual (Page 31)

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7.3 Zero Calibration
This procedure for recalibrating the zero point of the transducer 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 SZ, for SETUP ZERO.
5. If the 470 responds “NO CAL”, the program enable switch in Step 3 is not set. Transmit
C, for CLEAR, and restart this procedure.
6. The transducer responds “APPLY”, followed by the pressure required for zero calibration,
and continuously repeats this response until Step 8 is reached.
7. Apply the indicated pressure from a high accuracy standard.
8. When the pressure is stable, transmit S, for SETUP.
9. The transducer takes data and adjusts its zero calibration. If the new zero data indicates
that 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.
10. The 470 responds “PROTEC”. Set the program enable switch to “OFF”
(Section 7.2). Transmit C, for CLEAR, to resume normal operation.