PPC2+™ Operation and Maintenance Manual
©2001 DH Instruments, Inc.
Page 56
3 . 4 S P E C I A L M E N U K E Y
The [SPECIAL] menu key accesses a menu of functions that are less commonly used or not normally
used in regular operation.
Press the [SPECIAL] menu key to access the SPECIAL menu.
The display is:
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9ZO\K^SYXKXN7KSX^OXKXMO7KX_KV
3.4.1 AUTOZ
m
PURPOSE
To change the offset (zero) of the Lo and Hi reference pressure transducers relative to a
reference value in order to compensate for RPT zero drift between full recalibrations.
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=OM^SYXS^S]\OMYWWOXNON^RK^+_^YDLO\_X^RO`KV_OYPD900=/>_ZNK^ONK^
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PRINCIPLE
How AutoZ Works
The main component of the change over time of the PPC2+ RPTs is zero drift or offset,
independent of span. Rezeroing PPC2+ RPTs relative to a more stable reference
between recalibrations allows higher measurement accuracy specifications to be
maintained with less frequent full calibrations. The PPC2+ autozero function (AutoZ)
provides full on-board support for the rezeroing process to simplify its application by
the user.
The autozeroing function uses four parameters:
1. ZSTD: The value of the autozero pressure as indicated by the reference
autozero device.
For
absolute RPTs in absolute measurement mode
, the autozero pressure is always
atmospheric pressure and the ZSTD value can be supplied either a) by manual entry;
b)
automatically from a DHI
RPM connected to the PPC2+ COM2 port or;
c) automatically from a Lo absolute RPT if one is available.
For
gauge RPTs or absolute RPTs in gauge measurement mode
, the autozero
pressure is always zero (atmospheric pressure) which is supplied by definition when
the RPT is vented to atmosphere.
4Internal
Содержание PPC2+
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