DH Instruments PPC4, Operation And Maintenance Manual

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3. OPERATING PRINCIPLES
Page 53 © 2009 DH Instruments, a Fluke Company
operation as an external device to a PPC4, the TEST (-) valve is normally closed.
It is only opened when PPC4 is controlling with coarse pressure control.
Allows the TEST (-) vent valve to be set to be permanently open, permanently
closed or to operate in its default automated condition. It also allows the current
status of the valve to be viewed.
Note
•
The normal setting for the TEST (-) vent valve is Auto in
which PPC4 automatically controls the valve based on
current PPC4 operation. Manual settings should only be
selected by advanced users.
•
When the active Q-RPT is an external RPM4 Q-RPT, the
TEST (-) Vent operation applies to the RPM4 Q-RPT
module. The TEST (-) Vent settings made from the PPC4,
apply only as long as the RPM4 is a PPC4 external device.
When the RPM4 power is cycled, the RPM4 TEST (-) Vent
will return to its original state.
•
The TEST (-) Vent function setting always applies to the
active Q-RPT module, whether the module is internal to
PPC4 or in an external RPM4 (see the RPM4 Operation and
Maintenance Manual).

Caution
If the PPC4 detects a condition in which it determines there
could be a risk of overpressure to the RPT by opening the TEST
(-) Vent valve when a Manual Open is requested, a message
indicating a DP overpressure risk is displayed. If this message
is displayed, return to normal operation, vent the PPC4 and try
again.

OPERATION
For Basic Interface, see Section 4.5.7.5.
For Advanced Interface, see Section 5.7.12.5.
3.2.28 Calibration

PURPOSE
To calibrate the PPC4 utility sensor, Hi and/or Lo Q-RPTs and adjust the on-board barometer.
This function is considered part of PPC4 maintenance and is therefore covered in the
maintenance section of this manual (see Sections 7.2, 7.3 and 7.4).

OPERATION
See Sections 7.2, 7.3 and 7.4.
3.2.29 Measurement Uncertainty

PURPOSE
PPC4 has the ability to configure, calculate and display the uncertainty in pressure for each
controlled pressure target. The uncertainty value is available locally with the Advanced
Interface and is also available remotely in the response to the PRR command for all PPC4
models (see Section 6.5.4, PRR Command). Uncertainty can be defined with or without
control components (delivered or measured pressure uncertainty). Uncertainty components
are explained below and default values are given in Table 13.