PPC4™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company
Page 186
reference with greater measurement uncertainty may be used but PPC4 measurement
uncertainty may be degraded proportionally from published specifications.
•
If the Q-RPT is an Axxx (absolute) type and will be used in the absolute and/or
negative gauge measurement modes, the reference must be able to apply absolute
pressures:
Absolute pressures may be achieved either by operation relative to an
evacuated bell jar or, for higher pressures, by addition of atmospheric pressure measured
by a high accuracy barometer.
Axxx (absolute) Q-RPTs that will not be used in
absolute of negative gauge measurement modes (as is very often the case for
higher pressure Q-RPTs) do not require the application of absolute pressure for
calibration and may be calibrated using a gauge pressure reference.
Caution
Axxx (absolute) Q-RPTs calibrated in gauge measurement mode by
applying gauge reference pressure values should be used in gauge mode
only (see Sections 3.2.11, 7.2.5).
•
Able to supply the recommended sequence of pressure points in the range to
be calibrated:
See Section 7.2.4 for information on the recommended calibration point
sequence for various Q-RPT types and classes.
7.2.3
Set-up and Preparation
To set-up and prepare the PPC4 for calibration of an internal Q-RPT:
Set the PPC4 on a stable surface near the calibration standard at a height as close as
possible to the calibration standard’s reference height. Consider the connections that
may need to be made to the rear panel and access to the front panel display and keypad.
Connect a pressure supply greater than the maximum pressure to be applied during the
calibration to the PPC4 rear panel
SUPPLY
port (1/8 in. NPT F). (See Section 2.3.4)
If the calibration will include pressures under atmospheric pressure, connect a vacuum
pump to the PPC4 rear panel
EXHAUST
port (1/4 in. NPT F). There will be a constant
bleed of gas through the
EXHAUST
port so the vacuum pump should be self-venting or
disconnected when OFF (see Section 2.3.5).
Connect the calibration standard output to the PPC4 rear panel
TEST(+)
port (1/8 in. NPT F).
Caution
DO NOT apply pressure to the TEST(+) port without having a pressure
supply greater than the applied pressure connected to the SUPPLY port.
Do not cause sudden external pressure changes. Damage to internal PPC4
components could result. Unless the piston gauge used to calibrate the
PPC4 has automated pressure control, it is highly recommended that the
PPC4 direct pressure control keys (see Section 3.2.1) be used to slew and
adjust pressure during the calibration. This will minimize the risk of
accidental overpressure of the PPC4 Q-RPTs.
7.2.4
Recommended Calibration Point Sequence
Calibration adjustments to PPC4 Q-RPTs are made by adjusting calibration coefficients,
PA and PM (see Section 7.2.1.1). To adjust these coefficients to optimum values giving the
best results over the Q-RPTs complete operating range, specific calibration point sequences
are recommended. The recommended point sequence depends upon whether the Q-RPT
being calibrated is a Premium, Standard or Full Scale Standard Class (see Section 1.2.2.1).
The class of the PPC4 Q-RPTs is indicated on the model number on the product label and on
the rear panel Q-RPT model (
<p>
for premium,
<s>
for standard and
<f>
for full scale
standard - for example A7Ms or A7Mp).
Summary of Contents for PPC4
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