A20M-AF Reference Pressure Monitor with High Pressure Mounting System Operation and Maintenance Manual

3. OPERATION

3.3.3 [MODE]

 PURPOSE

To set the measurement mode (absolute, gauge) for the active range.

To select the unit of measure, use [UNIT] (see Section 3.3.2).

 PRINCIPLE

RPM4 A70M/A20M-AF supports simple, one-step switching between two measurement

modes:

Absolute Measures pressure relative to vacuum (zero is hard vacuum). Range is

from zero absolute to full scale.

Gauge Measures pressure relative to atmosphere (zero is ambient pressure).

Range is from zero gauge to full scale, full scale must be greater than zero.

The RPM4 A70M/A20M-AF Q-RPTs measure pressure relative to a sealed vacuum reference

and are intrinsically absolute. Gauge mode is accomplished by offsetting of atmospheric

pressure with dynamic compensation for atmospheric pressure changes between offsets

using an on-board barometer (see Section 3.2.2). Access to absolute operation can be

turned OFF (see Section 5.3.5).

When changing modes for a range, if the full scale of the range is 100 psi (700 kPa) or greater,

the full scale is the same in both absolute and gauge modes. If the full scale is less than 100 psi,

the gauge mode full scale is 14.5 psi (100 kPa) lower than the absolute mode full scale.

Measurement mode selection is range specific.

 OPERATION

To change the active measurement mode for a range,

press [MODE] from the MAIN RUN screen while the

range is active. The display is:

Measurement mode:

1absolute 2gauge

Select the desired measurement mode and operation returns to the main run screen with the

selected measurement mode active. If absolute measurement mode has been turned OFF in

calibration (see Section 5.3.5), absolute mode is not available.

Certain RPM4 settings, including AutoZ ON/OFF (see Section 3.5.1) are range AND

measurement mode specific. See Table 2 for a listing of settings and what they are specific to.

Absolute mode capability can be turned OFF in the calibration function (see Section 5.3.5).

When absolute mode is turned OFF, only gauge mode can be activated. <Gauge mode only, other

modes OFF> is displayed when [MODE] is pressed.

3.3.4 [AUTORANGE]

 PURPOSE

To automatically set up RPM4 to optimize its measurement characteristics and features for a

specific, user defined pressure range of operation.