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Copyright 1996 Baker Hughes Company.
20 | ADTS 403/405 Calibration Manual–English
Chapter 5. Calibration using IEEE 488 SCPI
the calculations. The required table of values depends on the control channel to be calibrated
and, for the pitot channel, the range of the sensor fitted.
Each calibration pressure has an associated residual error correction value stored in the ADTS.
This procedure is invalid if alternative calibration pressures (> ± 2 mbar of the given values) are
used because the residual corrections would no longer apply to the expected span point. If any
of the pressure points are missed, then the corresponding residual must be set to an assumed
value of zero.
The number of calibration points used is referred to as NUMPTS, a maximum of 12
points are
listed in the tables, this is so that all of the residual coefficients used in the ADTS 403/405 may
be calculated. The first calibration point is always zero, it is not necessary to apply it. The residual
error for this calibration point will be automatically set to zero as the error, at this point, is best
corrected by offset adjustment.
5.2 Defining Elements for a Program
5.2.1 Terms, Variables and Constants
The following terms, variables and constants are used in this section:
The elements to be used in the program are found or calculated in the following:
Table 5 - 1: Calibration Pressure Ranges
Port
Pressure Range Sensor Nominal Full Scale
Table of Applied
Pressures
inHg mbar inHg mbar
Static 40 1355 38.7 1310 Table 5 - 3
Pitot 850 knots 80 2700 77.4 2620 Table 5 - 4
Pitot 1000 knots 103 3500 101.9 3450 Table 5 - 5
Table 5 - 2: Terms, Variables and Constants
Item Description
STANDARD_PRESSURE Pressure measured or applied by the calibration standard (e.g., dead
weight)
STANDARD_PRESSURE(n) Array of standard pressures, indexed by n, in mbar.
AVE403/405(n)
Array of average pressures read from ADTS 403/405, in mbar.
OLDSLOPE Existing slope (span) value.
OLDOFFSET Existing offset (zero) value, in mbar.
R(0) to R(11) Residual values in PPM FS.
NUMPTS Number of calibration points (Max = 11).
MAXPTS Maximum number of points, set to 11.
PTSUSED Actual number of calibration pressures applied.
MAXSLOPE Maximum allowable slope change in % of reading (specified by user).
MAXOFFSET Maximum allowable offset change in mbar (specified by user).
FS Sensor full-scale taken from Table 5 - 1.
M Change in slope.
C Change in offset.