Table 11. Autoz On And Off - Fluke RPM4-AD Operation And Maintenance Manual

Reference pressure monitor, air data version

Table of Contents

When gauge or negative gauge mode is first activated, the value of P

from the absolute pressure reading to achieve gauge pressure is standard atmosphere of

101.325 kPa.

This can cause a large zero error when gauge mode is activated if

atmospheric pressure is significantly different from standard atmospheric pressure.

When gauge mode is activated, always press [AutoZ] to run AutoZ and obtain an actual

value of P

offset.G

AutoZ in differential measurement mode

RPM4-AD supports differential measurement mode (see Section 3.2.6) in which the

measured pressure is the difference between the pressure measured by the Hi Q-RPT (Pt)

and the Lo Q-RPT (Ps) (Hi – Lo, Pt – Ps).

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. In differential measurement mode, when the active unit of

measure is an airspeed unit, the line pressure is altitude. The value of P

measured by the Lo Q-RPT at the time of AutoZ.

In differential measurement mode, with AutoZ ON, differential pressure is calculated as:

In differential measurement mode, AutoZ is run when initiated by the operator pressing

[AutoZ].

RPM4-AD's differential mode AutoZ function connects both RPTs together

internally to the TEST (Ps) port to be sure they are exposed to the same pressure.

AutoZ ON/OFF

The AutoZ function can be turned ON and OFF, separately for gauge, absolute and

differential measurement modes and for each Q-RPT. Table 11 summarizes the effect of

AutoZ ON and OFF.

MEASUREMENT

MODE

Absolute

Gauge or

negative gauge

Differential

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-AD Q-RPTs and maximizing the recalibration interval by compensating for zero

drift between full recalibrations.

uncertainty in the differential pressure due to the offset between the Hi and Lo Q-RPTs at the

"line pressure" (altitude in air data measurement). The following simple recommendations

will help assure that you use the AutoZ feature to best advantage.

•

In gauge and differential measurement mode: Always leave AutoZ ON when operating.

•

In absolute measurement mode: Always leave AutoZ ON when operating if the AutoZ

routine has been run regularly using a valid atmospheric reference.

= P

- P

differential