Specifications

molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
© 1998-2007 DH Instruments, a Fluke Company Page 56
To edit the current P
offset
values, press [TARE], <4AutoZ>, <3edit>. The display is:
1. Edit field for the value of P
offset
of the upstream
(1, Hi) RPT.
2. Edit field for the value of P
offset
of the upstream
(1, Hi) RPT.
Poffset:18.7 Pa UP1
Poffset:-3.5 Pa DN2
Edit the P
offset
value(s) as desired and press [ENT] to activate the new value(s).
Press [ESC] to abandon changes.
The value of P
offset
is always displayed and entered in Pascal (Pa).
3.4.4.4.2 Run AutoZ
Run AutoZ is the function by which the current RPT reading is compared to a
reference, P
std,0
, at atmospheric pressure to determine a new value of P
offset
.
The value of P
offset
is then used by AutoZ to automatically correct the RPT for
possible change in zero over time (see Section 3.4.4.4, PRINCIPLE).
To access run AutoZ, press [TARE], <4AutoZ>, <4run>. The display is:
1. Selection of source of P
std,0
reference to which
to AutoZ.
AutoZ by:
1Entry 2COM2
Selecting <1Entry> allows the value of P
std,0
to be entered from the front panel keypad.
Selecting <2COM> allows the value of P
std,0
to be read automatically from a DHI
RPMx connected to molbox RFM’s COM2 communications port.
When AutoZ is run, the molbox RFM internal valves are actuated to connect both
molbox RPTs to the Hi port on the molbox RFM rear panel (see Figure 21 in
Section 5.2.4.1). Be sure the Hi port is fully open to atmosphere when running
AutoZ. Note that the molbox RFM quick connectors and molbox to molbloc
pressure lines are self sealing and therefore DO NOT open to atmosphere
unless a quick connector stem is inserted. Use a quick connector stem (DHI P/N
101889, equivalent to Swagelok SS-QM2-S-200) supplied with the molbox RFM
accessories to open the port to atmosphere.
Allow the molbox RFM to stabilize at atmospheric pressure and ambient
temperature for 10 to 15 minutes before running AutoZ.
If running AutoZ results in a value of P
offset
that is greater than ± 0.025 % FS of
the span of the RPT that is being AutoZeroed, the RPT and/or the reference
used as the source of Pstd,0 may be out of tolerance or the AutoZ process may
have been faulty. Before activating a new P
offset
greater than ± 0.025 % FS of
the active RPT, check to be sure that both the RPT and the reference were in
good working order, properly vented to stable atmospheric pressure, at the
same height, and reading in the same pressure units when AutoZ was run.