Fluke RPM4 manual AutoZ in gauge measurement mode with a Gxxx or BGxxx Q-RPT, AutoZ ON/OFF

RPM4™ OPERATION AND MAINTENANCE MANUAL

AutoZ in gauge measurement mode with a Gxxx or BGxxx Q-RPT

Q-RPTs with the designation Gxxx or BGxxx are intrinsically gauge. They have an atmospheric (TEST(-)) reference port and measure gauge pressure (difference from atmosphere).

In gauge measurement mode the value of Pstd,0 is always zero gauge pressure. Zero gauge pressure, by definition, is applied to the Q-RPT when it is vented to atmosphere.

When using a Gxxx Q-RPT in gauge measurement mode, with AutoZ ON, gauge pressure is calculated as:

Pgauge = Pu - Poffset,G

In gauge measurement modes, AutoZ is run when initiated by the operator pressing [AutoZ] when the RPM4 is vented. This assures the regular automated updating of the Poffset,G value.

AutoZ in differential measurement mode

RPM4s with two Q-RPTs of the same type (Axxx, Gxxx, BGxxx) support differential measurement mode (see Section 3.3.3.1) in which the measured pressure is the difference between the pressure measured by the Hi Q-RPT and the Lo Q-RPT (Hi – Lo).

In differential measurement mode, the purpose of AutoZ is to compensate for the offset between the Hi and Lo Q-RPT indications at the “line pressure” at which the differential pressure is being measured. The value of Pstd,0 is the pressure indicated by the Lo Q-RPT at the time of AutoZ.

When using an RPM4 with two Q-RPTs in differential measurement mode, with AutoZ ON, differential pressure is calculated as:

Pdifferential = PHi - PLo - Poffset,D

In differential measurement mode, AutoZ is run when initiated by the operator pressing [AutoZ] when both Q-RPTs of the RPM4 are connected to a common pressure..

AutoZ ON/OFF

The AutoZ function can be turned ON and OFF, separately for gauge, absolute and differential measurement modes. Table 7 summarizes the effect of AutoZ ON and OFF.

Table 7. AutoZ ON and OFF

Q-RPT	MEASUREMENT	AutoZ	Poffset	ΔPatm	AutoZ
					ROUTINE
TYPE	MODE	STATUS	APPLIED	APPLIED
					RUNS
		ON	YES		When initiated
	Absolute			Not Applicable	by operator
Axxx		OFF	NO		Not available
	Gauge or	ON	YES	YES	When initiated
	negative gauge				by operator
		OFF		NO
Gxxx	Gauge or	ON	YES		When initiated
or					by operator
BGxxx	negative gauge			Not Applicable
		OFF	NO		Not available
Any, Hi Q-RPT		ON	YES		When initiated
	Differential			Not Applicable	by operator
in dual Q-RPT
RPM4		OFF	NO		Not available

Recommendations for the Use of the AutoZ Function

The AutoZ function provides a powerful and easy to use tool for improving the stability over time of RPM4 Q-RPTs and maximizing the recalibration interval by compensating for change in zero between full recalibrations. In differential measurement mode, it minimizes the uncertainty in the differential pressure due to the offset between the Hi and Lo Q-RPTs at the

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