Fluke molbox RFM Data sheet
™
molbox RFM
Reference Flow Monitor
Technical Data
Features
• Compact presentation
• Covers the flow range of 1 sccm to
100 slm with molbloc-L, and up to
5000 slm with molbloc-S
• Select from 20 different gases with
molbloc-L and 10 with molbloc-S
• Accredited measurement uncertainty
of ± 0.5 % of reading with 100:1
rangeability
• Internal valving for on-board purge,
leak test and tare support
• Includes advanced measurement
functions such as totalize, average,
hi/lo and deviation
• Complete front panel control and
RS232 and IEEE-488 remote
communications
• Measures mass and volume flow with
user setable reference pressure and
temperature conditions
molbox RFM is a support unit
for making mass flow measurements using molbloc-L
laminar and molbloc-S sonic
flow elements.
molbloc flow elements are
connected to molbox RFM with
two pressure connections and
one data line. molbox RFM reads
calibration data off the molbloc
EEPROM and measures molbloc
upstream and downstream
pressure with its built-in high
accuracy Reference Pressure
Transducers (RPTs). An ohmic
measurement system reads
the resistance of the molbloc
platinum resistance thermometers from which molbloc
temperature is calculated. Using
the molbloc calibration data,
pressures, temperature and gas
properties stored in molbox RFM
memory, the flow rate of the gas
flowing through the molbloc is
calculated. For molbloc-L flow
elements, a microrange option
is available to increase flow
measurement resolution and
accuracy under 10 % FS of the
flow range.
molbox RFM and molbloc flow
elements are useful in a variety
of measurement, test and calibration applications in which
highly accurate measurement of
low gas flows where maximum
accuracy is the most notable
specification is needed. molbox
RFM is specifically designed for
applications in which a highly
compact presentation, great
rangeability and reduced cost
are the primary considerations.
A second model, molbox1, is
available for applications in
which lowest possible uncertainty is the top priority.
To configure your mass flow
calibration system, see the
pages that follow to select the
molbloc and pressure dependent calibrations to best cover
your flow ranges and pressure
conditions. molstic mounting
systems and COMPASS® for
molbox calibration software
are available to complete the
system (see molstic and
COMPASS product brochures).
Flow measurement specications
molbox RFM measures the flow through molbloc flow elements. The flow range, usable
operating pressure, and differential pressure for molbloc-L, or the flow range and absolute
pressure range for molbloc-S, depend on the molbloc element used and the calibration
options. For molbloc-L ranges up to 3E4, the resolution and accuracy under 10 % FS are
improved by the microrange option. For the 1E5-L molbloc, the microrange option is
necessary to achieve the specification.
molbox RFM
molbloc-L (ranges 1E1-L thru 3E4-L) molbloc-S (all ranges)
Measurement
update rate
Range 0 to molbloc full scale depending on gas and molbloc pressure
Resolution 0.01 % FS ± 0.01 % of reading
Linearity ± 0.23 % of reading from 10 % to 100 % FS,
Repeatability ± 0.1% of reading from 10 % to 100 % FS,
1
Precision
Predicted stability
(one year)
Measurement
uncertainty
3
1 second 1 second
dependent calibration type (see molbloc-L tables)
± 0.023 % FS under 10 % FS
± 0.01% FS under 10 % FS
± 0.25 % of reading from 10 % to 100 % FS,
± 0.025 % FS under 10 % FS
2
± 0.15 % of reading from 10 % to 100 % FS,
± 0.015 % FS under 10 % FS
± 0.5 % of reading from 10 % to 100 % FS,
± 0.05 % FS under 10 % FS
The flow related to 20 kPa to 200 kPa absolute (3 psia to 30 psia)
or 50 kPa to 500 kPa absolute (7 psia to 70 psia) upstream
(see molbloc-S table)
± 0.25 % of reading
± 0.1 % of reading
± 0.3 % of reading
± 0.2 % of reading
± 0.5 % of reading from 50 kPa to 500 kPa, ± 0.5 % of the flow @
50 kPa from 20 kPa to 50 kPa
molbox RFM with Microrange option
molbloc-L (ranges 1E1-L thru 3E4-L) molbloc-L (ranges 1E5 only)
Measurement
update rate
Range 0 to molbloc full scale depending on gas and molbloc pressure
Resolution 0.01 % FS, 0.001 % FS under 10 % FS 0.01 % FS
Linearity ± 0.23 % of reading from 1 % to 100 % FS,
Repeatability ± 0.1 % of reading from 1 % to 100 % FS,
1
Precision
Predicted stability
(one year)
Measurement
uncertainty
1
Precision: Combined linearity, hysteresis, repeatabil ity.
2
Predicted S tabi lity: Max imum change in zero and span over one year for typical molbox R FM
and molbloc used under typical condit ions. A s sta bility ca n only be predicted, stabilit y for a
specific mol box RFM should be es tabl ished from experience.
3
Measu rement Uncertainty: Ma ximum dev iation of the mol box R FM flow i ndic ation f rom the
true value of t he flow through the mol bloc including precision, sta bil ity and DHI calibration
standard u ncer tainty. Meas urement uncerta inty specificat ions for molblocs are valid only
for gases with which the molbloc has been ca librated. All molbloc s are c ali brated for N2.
Cali brations with other gases are optiona l. DHI calibrat ion capabil ity is not mai ntai ned at
all times for all ga ses on a ll molbloc des ignations . Check for avai labilit y before ordering.
3
1 second 1 second
dependent calibration type (see molbloc-L tables)
± 0.0023 % FS under 1 % FS
± 0.001 % FS under 1 % FS
± 0.25 % of reading from 1 % to 100 % FS,
± 0.0025 % FS under 1% FS
2
± 0.15 % of reading from 1 % to 100 % FS,
± 0.0015 % FS under 1 % FS
± 0.5 % of reading from 1 % to 100 % FS,
± 0.005 % FS under 1 % FS
molbloc-S (all ranges)
Specifications are the same as a molbox RFM
without Microrange. The Microrange transducer is disabled whenever the molbox RFM is
connected to a molbloc-S.
0 to molbloc full scale depending on gas and molbloc pressure
dependent calibration type (see molbloc-L tables)
± 0.25 % of reading from 5 % to 100 % FS,
± 0.0125 % FS under 5 % FS
± 0.2 % of reading from 5 % to 100 % FS,
± 0.01 % FS under 5% FS
± 0.32 % of reading from 5 % to 100 % FS,
± 0.016 % FS under 5 % FS
± 0.2 % of reading from 5 % to 100 % FS,
± 0.01 % FS under 5 % FS
± 0.5 % of reading from 5 % to 100 % FS,
± 0.025 % FS under 5 % FS
2 Fluke Corporation molbox RFM™ Reference flow monitor
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