Molbloc-S Operation - Fluke MOLBOX RFM Operation And Maintenance Manual

If the new tare is > 10 000 Pa, the new tare cannot be activated.
Pressing [ENTER] or [ESCAPE] returns to the tare screen.
molbox RFM needs service or a grossly incorrect adjustment has been made to
one or both of the RPTs.
Microrange differential pressure RPT zero drift test (if microrange
option present): When attempting to activate a new tare, molbox RFM checks
the zero offset value of the microrange RPT. If the new tare is > 999 Pa, the new
tare cannot be activated. Press [ENTER] or [ESCAPE] to go back to the tare
screen. It is likely that molbox RFM needs service or a grossly incorrect
adjustment has been made to the differential RPT.
If a caution message appears or a tare cannot be activated during the taring
process, repeat the taring process. If the caution persists, the calibration
of the RPT(s) should be verified. If the tare still cannot be activated, the
RPT(s) should be recalibrated and molbox RFM may require other service.
3.4.4.1.2

molbloc-S Operation

PURPOSE
To check the molbox RFM RPT absolute pressure readings by comparing them
at a common molbloc-S upstream absolute pressure.
PRINCIPAL
When measuring the flow through molbloc-S, the critical pressure measured by
molbox RFM is the molbloc upstream pressure. The downstream pressure is
only monitored to be sure that critical flow conditions exist (see Section 3.1.2). To
reduce the uncertainty on the upstream pressure measurement, molbox RFM
employs internal valving to direct the upstream pressure to both RPTs, and the
average of the two readings is used as the measured molbloc upstream
pressure. To take advantage of this RPT averaging, the molbox RFM must be in
either BPR OFF or Auto BPR mode (see Section 3.6.9).
molbox RFM dynamically tares the two RPT readings when they are connected
together, so the user can view the "live" average pressure that is calculated
and to allow smooth pressure and flow measurements during valve transitions
in the Auto BPR mode (see Section 3.6.9). RPT taring in molbloc-S operation
occurs automatically when needed and does not need to be initiated or
performed by the user.
The molbloc-S TARE function is available to allow the user to conveniently verify
that the two RPT measurements agree within an acceptable tolerance when a
common pressure is applied to them. When the TARE function is selected, the
molbox RFM internal valves operate to connect both Q-RPTs the active channel
UPSTREAM pressure port (see Figure 6). The RPT readings and the difference
between the two RPT readings (tare value) is displayed for evaluation by the user.
A message is also displayed to indicate to the user whether the tare value is
acceptable, or indicates a need for pressure verification or calibration of the RPTs.
There is no need for the customer to save a new tare value during molbloc-S operation.
As during molbloc-L operation, the molbloc-S tare value is the difference
between the two transducer readings (hi - lo). In BPR modes where the tare
value is dynamically calculated and applied, the upstream RPT is corrected by
(- tare value/2) and the downstream RPT is corrected by (+ tare value/2).
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3. OPERATION
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