EM1NR SENSIRION, EM1NR Datasheet - Page 5

• Manufacturer Part Number: EM1NR
• Description: Flow Sensor
• Manufacturer: SENSIRION

Specifications of EM1NR

• Pressure Max: 116psi
• Accuracy: ± 3% At 1-100% Full Scale
• Flow Range: 0-20 Ln/min
• Sensing Accuracy: 3%
• Output Type: RS 232/SPI
• Supply Voltage Max: 18VDC
• Flow Rate Min: 0l/min
• Pressure Drop: 0.29psi
• Supply Voltage Min: 7VDC
• Sensor Output: RS-232/SPI
• Rohs Compliant: Yes
• Flow Rate Max: 20l/min
• Accuracy %: 3%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

CMOSens
1.1 Gas Flow Characteristics
Figure 2 shows the applied gas flow vs. the digital
output of the CMOSens
200 ln/min version.
Figure 2: Typical CMOSens
transfer characteristics.
The CMOSens
from 0 ln/min up to a flow of 200 ln/min (depending on
the actual type). Between 200 ln/min and 220 ln/min
flow is displayed, but with reduced accuracy. Two types
of overflows are reported outside of this expanded
range:
1.2 Sensor Principle and Gas Types
The CMOSens
gas flow by measuring heat transfer. A heating resistor
on a thermally insulated membrane is kept above
ambient temperature. In the presence of gas flow, the
temperature distribution up- and downstream is
disturbed. This asymmetry is then measured. Due to
the minimal thermal mass of the membrane,
symmetrical arrangement, and accurate temperature
measurement, the very good specifications of the
CMOSens
The above mentioned thermal principle requires
information about the gas type to be measured. The
www.sensirion.com
250
200
150
100
50
1. ‘Peak Overflow’ if the measured flow was only
2. ‘Overflow’ if the measured flow is always
0
0
partly above i.e. 220 ln/min. In this context it
has to be remembered that the CMOSens
EM1 Mass Flow Meter averages the flow over
a eligible integration time. It can be that the
average flow is small but that it periodically
exceeds the maximum of 220 ln/min and no
precise measurement of the average can be
guaranteed anymore. This can be checked
with a sensor readout at 200 Hz.
above the limit of 220 ln/min
®
®
EM1 Mass Flow Meter are achieved.
EM1 Mass Flow Meter for Gases
®
®
50
EM1 Mass Flow Meter detects mass
EM1 Mass Flow Meter is calibrated
Mass Flow [ln/min]
®
100
EM1 Mass Flow Meter for the
®
EM1 Mass Flow Meter
150
Data Sheet EM1 - v 3.0 / March 2009
200
250
®
CMOSens
gas types are available on request.
In Figure 3 the repeatability of the CMOSens
devices is compared with the repeatability of a typical
Mass Flow Controller (MFC). It emphasizes the
superior performance of the CMOSens
Flow Meter.
Figure 3: Comparison of the repeatability of the
CMOSens
Controller (MFC).
1.3 Temperature Compensation
The CMOSens
automatic temperature compensation implemented.
The flow measurement must be suspended for the
duration of each update of the temperature
measurement. Since these interrupts of the flow
measurement
measurements are only done with a reduced accuracy.
They can vary between different measurements and
reduce the accuracy of the temperature compensated
flow output. The duration of the temperature update is
45 ms which gives a variation of the output of the
compensated flow by 0.1% of measured value (for N2).
Advanced users can choose duration and accuracy of
the temperature updates and reduce the inaccuracy of
the temperature compensation even more.
The moment of a temperature update can be controlled
in two modes:
a) Automatically
b) By Hand
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
The temperature measurements are updated
automatically in fixed periods which can be set
by the command INT (see 0).
For highest accuracy it is recommended to set
INT=0 and initiate the updates through the
RS232 interface with UPDATETEMP (see 0).
For such measurements it also makes sense
to use the option for advanced users to set the
®
®
EM 1 compared to a typical Mass Flow
EM1 is available for air and nitrogen. Other
®
shall
20
EM1 Mass Flow Meter has an
be
40
Flow in [%FS]
short
CMOSens® EM1 Flow
Meter
Typical Conventional Flow
Meter with 0.3%FS
60
the
®
temperature
EM1 Mass
80
®
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