Sensors High Speed (2,500Hz)Exhaust Flow Meter

1. SEMTECH®
EFM-HS
High Speed Exhaust Flow Meter
Sensors’ High Speed Exhaust Flow Meter, the SEMTECH EFM-HS, adds
exciting capabilities and features to the product line. With a sampling rate
of up to 2500 Hz and four, dual stage differential pressure transducers, the
EFM-HS accurately measures every forward and reverse flow pulsation from
idle to maximum flow rate, and properly accounts for these pulsations in
the exhaust flow determination. This is a tremendous advantage over low
speed exhaust flowmeters which are susceptible to measurement error
from high frequency pulsations. The EFM-HS also offers a long list of other
performance enhancements and convenience features that set it apart
from the competition.
Mass flow rate accuracy and linearity of the SEMTECH EFM-HS exceeds the
US and European performance standards over a 50:1 turndown ratio. The
EFM-HS can be used to measure exhaust flow rate from both spark and
compression ignition engines, as a stand-alone device, or in conjunction
with the emissions measurements of the SEMTECH-DS or other gas
analyzers, to compute real-time mass emissions.
Emissions
Measurement
Solutions

2. 2
SEMTECH EFM-HS
High Speed Exhaust Flow Meter
Optional Configurations
High Speed Data Acquisition: Data output rate of 500 Hz is
available.
Stand-AloneConfiguration:SENSORTech-EFMHS application
enables system operation from a Windows environment.
Dual Channel Configuration: A second channel with a
full set of transducers can be added to the system in the
same electronics module. This is useful for measuring
a dual exhaust system, exhaust and EGR simultaneous
measurement, or detecting undeveloped flow conditions.
Customized Interface: Sensors can develop a customized
device driver to interface with various host systems.
System Features and Benefits
High Speed Sampling: The EFM-HS internally samples the differential
pressure channels at up to 2500 Hz, accounting for every pressure
pulse from an engine, from idle to maximum rpm. Standard output
rate is 5 Hz.
Embedded Calibration: Calibration coefficients embedded in the flow
tube electronics are automatically recognized on connection, enabling
multiple tubes to be used with one control module.
Multiple Tube Sizes: Eight flow tube sizes accommodate engines from
less than 0.8L displacement up to 24L.
Back Purge: A software controlled back purge pump is included in
the flow tube assembly along with solenoids that route high pressure
air backward through the pitot tube, purging contaminants and any
condensation in the pressure lines. No dismantling is required.
Auto Zero: With a single software command, internal solenoids open
the pressure sensors to ambient air, allowing fast and easy zeroing
while the engine is still operating.
Weatherproof Construction: The unit can be used off-road and in
other harsh environments. All components are weatherproof to IP54
(NEMA 3) standards.
Heated Components: The averaging pitot tube and pressure lines are
heated at the flow tube assembly in order to prevent condensation
and freezing in cold weather. The differential pressure sensors are
housed in a temperature controlled manifold in the control module
for added stability.
Sample Screen from SENSOR Tech-EFMHS

3. 3
SEMTECH EFM-HS
High Speed Exhaust Flow Meter
The Technology
Operating under the Bernoulli principle, the
SEMTECH EFM-HS uses four high performance,
dual-stage, differential pressure transducers,
sampling continuously at up to 2500 Hz,
measuring every pressure pulse from an engine.
The sensors are housed in a heated manifold,
eliminating thermal drift. The eight combined
differentialpressurerangesspannearlyfiveorders
of magnitude, allowing accurate measurements
over a wide range of flow rates. The smallest
transducer range is 0.025 kPa with a resolution of
5x10-5
kPa, while the highest range is 16.5 kPa.
A proprietary algorithm computes a spline fit of the
eight high speed differential pressure signals, and
calculates a running square-root average that is used
to determine output flow rates at 5 Hz (500 Hz with
the high speed option). The high speed sampling
and symmetrical design of the averaging pitot tube
provides the EFM-HS with the ability to accurately
measure reverse flow due to engine pulsations, and
to properly account for this phenomenon in the
average flow rate determination.

4. Sensors, Inc. • 6812 State Rd. • Saline, Michigan 48176 • PH:(734) 429-2100 • FX:(734) 429-4080 • www.sensors-inc.com
Sensors Europe GmbH • Feldheider Str. 60 • 40699 Erkrath • Germany • PH: +49 (0) 2104-14188-0 • FX: +49 (0) 2104-14188-14
SEMTECH EFM-HS Available Sizes and Flow Rates
Recommended Application: Engine Size (L) & Type
Gas
Diesel
< 1†
< 0.8
< 2†
< 1.5
< 2
< 1.5
2 - 5
1.5 - 4
> 5
4 - 6
-
6 - 12
-
12 - 18
-
> 18
Flow Tube Outer Diameter
in
mm
1
25
1.5
38
2
51
2.5
64
3
76
4
102
5
127
6
152
Flow Tube Length (Length including extension)
in
mm
20 (26)
508 (660)
20 (26)
508 (660)
20 (26)
508 (660)
25 (32.5)
635 (825)
25 (34)
635 (864)
25 (37)
635 (940)
30 (45)
762 (1143)
36 (54)
914 (1372)
Backpressure Flow rate at 200°C, SCFM (m3
/min)
10” H2
0
2.5 kPa
67
(1.9)
109
(3.1)
175
(4.9)
425
(12.0)
600
(17.0)
1100
(31.2)
1700
(48.1)
2380
(67.3)
15” H2
0
3.75 kPa
83
(2.4)
146
(4.1)
215
(6.1)
550
(15.6)
775
(22.0)
1350
(38.2)
2100
(59.5)
2940
(83.3)
Backpressure Flow rate at 400°C, SCFM (m3
/min)
10” H2
O
2.5 kPa
56
(1.6)
91
(2.6)
147
(4.2)
356
(10.0)
503
(14.3)
922
(26.2)
1425
(40.3)
1995
(56.4)
15” H2
O
3.75 kPa
69.6
(2.0)
122
(3.5)
180
(5.1)
461
(13.1)
649
(18.4)
1132
(32.0)
1760
(49.9)
2465
(69.8)
†
Non-Turbo
NOTE: Specifications are subject to change without no-
tice. While due caution has been exercised in the produc-
tion of this document, possible errors and omissions can
occur.
R 05/10
4
SEMTECH EFM-HS
High Speed Exhaust Flow Meter
Exhaust temperature range: -5 to 700°C standard construction (higher temperature capability available
upon request)
Exhaust temperature accuracy: ± 1% of reading or ± 2°C, whichever is greater
Flow measurement linearity: < 1.0% of full scale
Exceeds 1065 Subpart D and ISO 16183 standards
Flow measurement accuracy: ± 2% of reading or ± 0.5% of full scale, whichever is greater
Warm up time: < 5 minutes at 20°C ambient
System response time: < 2 ms
Data rate: 5 Hz standard
High Speed option data rate: 500 Hz (100 Hz display rate)
Resolution: 0.1 SCFM
Power requirements: 12VDC , 30W; 110VAC
Communications: RS 232
Control module dimensions: 36cm x 18cm x 10cm (LxDxW)
Control module weight: 4kg (9 lbs)
Length*
Diameter*
69.0mm
381.0mm
49.0mm
*see chart above.
NOTE: Accurate measurments require adequate straight
pipe length prior to the exhaust entering the measuring
pitot. This is ensured with our tube extension kits, refer-
enced in the length specifications in the chart above.