DH Instruments PPC3 - Overview; Calibration of Quartz Reference Pressure Transducers (Q-Rpts); Principle

5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 121 © 2002-2007 DH Instruments, a Fluke Company
5
5
.
.
M
M
A
A
I
I
N
N
T
T
E
E
N
N
A
A
N
N
C
C
E
E
,
,
A
A
D
D
J
J
U
U
S
S
T
T
M
M
E
E
N
N
T
T
S
S
A
A
N
N
D
D
C
C
A
A
L
L
I
I
B
B
R
R
A
A
T
T
I
I
O
O
N
N
5.1 OVERVIEW
PPC3 was designed for maintenance free operation. No maintenance is required other than:
• Regular rezeroing of quartz reference pressure transducers (Q-RPT), if present (see Section 3.5.1).
• Periodic calibration of Q-RPTs, if present (see Section 5.2).
• Adjustment of the on-board barometer and/or utility sensor, if present (see Sections 5.3, 5.4).
• Automated adjustment of pressure controlling parameters, as needed (see Section 5.5).
This section provides information on maintenance, adjustment and calibration procedures, and recommended
overhaul procedures.
PPC3 is a sophisticated pressure setting and measuring instrument with advanced on-board features
and functions. Before assuming that unexpected behavior is caused by a system defect or breakdown,
use this manual and other training facilities to become thoroughly familiar with PPC3 operation. For
rapid assistance in specific situations use the troubleshooting guide in Chapter 6.
PPC3 is covered by a limited one (1) year warranty. Unauthorized service or repair during the warranty
period is undertaken at the owner’s risk and may cause damage that is not covered under warranty
and/or may void the warranty.
5.2 CALIBRATION OF QUARTZ REFERENCE PRESSURE
TRANSDUCERS (Q-RPTS)
5.2.1 PRINCIPLE
PPC3 may be equipped with one or two quartz reference pressure transducers (Q-RPTs)
that are the source of low uncertainty pressure measurement for the system.
To calibrate a Q-RPT, pressures from a standard are applied to the Q-RPT at ascending and
descending points over the range. The recommended pressure sequence for a calibration
varies depending on whether the Q-RPT is of Standard or Premium class (see Section 1.2.2.1).
The pressure defined by the standard and the corresponding Q-RPT readings are recorded
at each point. After all of the pressures have been applied and recorded, adjustments are
made to fit the Q-RPT pressure readings to the standard. Fitting the readings means
performing a linear regression to arrive at the lowest value of the residuals of errors of the
Q-RPT relative to the standard. The Q-RPT output is adjusted by user settable coefficients:
PA (an adder or offset) and PM (a multiplier or span adjustment) (see Section 5.2.1.1).
The calibration process is performed independently on each Q-RPT to arrive at its optimal fit.