Meriam Laminar Flow
Elements (LFEs) are
excellent for measuring
low gas flow rates from
0.2 SCCM up to 2250 SCFM.
They are inherently
accurate and repeatable
and are calibrated
traceable to NIST in our
ISO 17025 certified Flow
Lab. Flow turndown is
20:1 or better and the
differential pressure
generated is nearly
linear to flow. This
combination makes an LFE
a great choice for gas
flow measurement and
flow control
applications.
Meriam LFE
Performance
Standard LFE calibration
accuracy is ± 0.72% of
Reading (not % of Full
Scale) traceable to the
National Institute of
Standards and Technology
(NIST). Rigid
construction and lack of
any moving parts make
the LFE calibration
stable. Only physical
damage or particulate
deposition in the
element will cause a
calibration shift.
Meriam LFE
Utility
LFEs can be used to
measure flow rate for a
variety of gases and
applications. Standard
models are available to
measure as little as 0.2
SCCM (5.9 E-06 SCFM) to
as much as 2250 SCFM of
air flow at standard
conditions. Custom
models for up to 15,000
SCFM of air are
available. Stainless
steel or aluminum
materials make LFEs
compatible with most
gases. Flow rate of gas
mixtures can also be
measured when the
percentages of component
gases and mixture
properties are known.
The Meriam LFE Matrix
The LFE matrix can be
made from individual SS
tubes or windings of SS
foil. These tubes are
long enough, relative to
their inside diameter,
to cause laminar flow to
occur inside each tube.
The result is a near
linear relationship
between DP and flow
rate. The DP generated
across the matrix
responds very quickly to
changes in flow. All DP
is permanent pressure
loss to the system but
LFEs are sized to
produce no greater than
8” water column at
maximum flowing
conditions. Individual
tube diameters are very
small so flowing gases
need to be clean and dry
to preserve the
calibration. Filtered
inlet versions of most
LFE models are available
to keep the matrix clean
and the calibration
constant.
Meraim
Calibration and Accuracy
Meriam LFEs are
calibrated with air at
atmospheric conditions
referenced to 29.92”
mercury absolute (760mm
Hg. Abs.) and 70ºF
(21.1ºC). Each completed
element is calibrated
and traceable to the
National Institute of
Standards and
Technology. Our Special
Calibration Procedure
#A-33544 is designed to
meet the basic
requirements of
MIL-STD-45662A, ANSI
Z540, 10CFR50 and
MIL-Q-9858A.
Meriam LFEs are supplied
with a reproducible flow
curve in terms of SCFM
versus inches of water
differential pressure.
Correction factors are
included to cover an
inlet pressure range
from 26 to 36” Hg Abs.
and an inlet temperature
from 50ºF to 150ºF. For
special flow
applications, contact
Meriam with complete
flow information. The
rated accuracy* of all
Meriam LFEs is
percentage of actual
reading; not the much
wider percentage of full
scale flow rate
tolerance of other
devices.
