Setra System Model 470 - Manual (Page 30)

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SECTION SEVEN
Calibration
7.1 Calibration
The zero and span of the Setra 470 Digital Pressure Transducer may be calibrated using the
procedures in Section 7.2 - 7.4. A high accuracy primary pressure standard is recommended as
the calibration source, since the high accuracy of the Setra 470 is adversely affected if the
calibration pressure is not of greater accuracy.
The calibration procedure requires the same pressures, in the same engineering units (usually
PSI), as were originally calibrated at the factory.
During calibration, note that the transducer reports a prompt message, not the actual pressure
applied, and cannot be used to monitor the pressure being applied during the calibration proce-
dure.
7.2 Calibration and Program Enable
The calibration data and coefficients for the 470 are stored internally in a nonvolatile memory.
This memory is protected from accidental erasure or disruption by a switch* on the digital elec-
tronics board. When the switch is set to “OFF”, the nonvolatile memory cannot be written over
deliberately or accidentally.
The 470 internal firmware checks the switch and requires it to be “ON” in order to execute any
calibration procedures, and requires it to be “OFF” for normal operation.
1. Locate the enable switch. It is located behind the round access hole in the transducer
case directly to the right of the communications port.
2. Immediately before beginning any calibration programming functions, the switch must be
set to “ON”. The procedures which require this refer you to this section of the manual.
a) If the enable switch is set to “ON’ before the power is applied to the 470, after its
internal power-up sequence it responds “PROTEC” rather than with its normal verify
message. If this occurs, remove power from the unit, set the switch to “OFF”, and
reapply power. Only set the switch to “ON” immediately before the calibration procedure
is executed.
b) If you transmit the command for a function which requires the enable switch, before
setting the switch to “ON”, the 470 will respond “NO CAL”. This is an indication that the
switch is in the “OFF” position.
To continue the procedure, set the switch to “ON” and transmit S, and resume.
*Note: Switch may be a dip switch or a header (pins) which can be temporarily con-
nected.