7Micro - Fluke MOLBOX RFM Operation And Maintenance Manual

The molbox RFM RS232 test can fail for three reasons:
1. The RS232 cable being used is incorrect (see Section 4.2.1.1 for
information on the correct cable).
2. COM1 and COM2 do NOT have the same serial communications settings
and therefore cannot communicate together (see Section 3.6.6.1 to set
the COM ports).
3. COM1 or COM2 is defective.
The reason for failed communications is almost always a cable or incorrect
RS232 interface settings. Be sure that these are correct before concluding
that a COM port is defective.
3.6.7 <7MICRO>
PURPOSE
To turn ON and OFF manual operation of the OPTIONAL MICRORANGE FLOW
MEASUREMENT function.
See also Sections 3.1.5 and 3.4.7 for additional information on the optional microrange
measurement option.
Manual microrange is intended for special uses of the microrange option as explained in
PRINCIPLE of this section. Normal use of the microrange is in automatic operation using
the MICRO function (see Section 3.4.7).
PRINCIPLE
The molbox RFM microrange option (if present) improves molbox RFM flow measurements
below 10 % FS of the measurement range. See Section 1.2.4.1.1 for a complete description of
microrange principles. The differences between automatic microrange and manual microrange
are that in manual microrange:
The differential pressure value used to calculate flow is either 100 % difference between the
upstream and downstream absolute RPTs (P1 - P2) or 100 % readings from the microrange
differential RPT. No special transitioning from one method to the other is applied.
The current source of the differential pressure measurement used to calculate flow is indicated
by the microrange option designator character in the main run screen (<d> when the source is
the microrange differential RPT; <a> flashing when the source is the difference between the
upstream and downstream absolute RPTs).
Pressing [SPECIAL] and selecting <7micro> allows manual microrange to be turned ON and
OFF. With manual microrange OFF, the microrange option differential pressure RPT
measurements are not used at all (unless automatic microrange is ON, see Section 3.4.7).
With manual microrange option ON, the differential pressure value used to calculate mass
flow is either the difference between the upstream and downstream RPTs if differential
pressure is > 12.5 kPa (1.8 psi) or the microrange differential RPT if differential pressure is <
12.5 kPa (1.8 psi).
The microrange option can also be operated in automatic mode (see Section 3.4.7).
Page 89 © 1998-2007 DH Instruments, a Fluke Company
3. OPERATION