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Hot-film air-mass meter, type HFM 2 54
Air-mass meters
A
B
Hot-film air-mass meter, type HFM 2
Measurement of air-mass throughflow up to 1080 kg / h
Technical data / Range
Part number
0 280 217 102
0 280 217 120
0 280 217 519
0 280 217 801
0 280 217 107
Characteristic curve
1
2
3
4
Installation length L
mm
130
130
130
130
96
Air-flow measuring
range
kg · h
1
10...350
10...480
12...640
20...1080
Accuracy referred to
measured value
%
±4
±4
±4
±4
Supply voltage
V
14
14
14
14
Input current
at 0 kg · h
1
A 0,25 0,25 0,25 0,25
at Q
m nom.
A 0,8 0,8 0,8 0,8
Time constant
1
)
ms 20 20 20 20
Temperature range
Sustained
°C
30...+110
30...+110
30...+110
30...+110
Short-term
°C
40...+125
40...+125
40...+125
40...+125
Pressure drop
at nominal air
mass hPa
mbar
<15
<15
<15
<15
Vibration acceleration
max.
m · s
2
150
150
150
150
1
) In case of sudden increase of the air-mass flow from 10 kg · h
1
auf 0.7 Q
m nominal
, time required to reach 63%
of the final value of the air-mass signal.
Q
m
U
Measurement of air mass
(gas mass) throughflow per unit
of time, independent of density
and temperature.
Extensive measuring range.
Highly sensitive, particularly
for small changes in flow rate.
Wear-free since there are no
moving parts.
Insensitive to dirt and
contamination.
Application
Measurement of air-mass flow rate to
provide data needed for clean combustion.
Air-mass meters are suitable for use with
other gaseous mediums.
Design and function
The sensor element comprises a ceramic
substrate containing the following thick-film
resistors which have been applied using
silk-screen printing techniques: Air-temper-
ature-sensor resistor
R , heater resistor
R
H
, sensor resistor
R
S
, and trimmer resistor
R
1
.
The heater resistor
R
H
maintains the
platinum metallic-film resistor
R
S
at a
constant temperature above that of the
incoming air. The two resistors are in close
thermal contact.
The temperature of the incoming air in-
fluences the resistor
R with which the
trimmer resistor
R
1
is connected in series.
Throughout the complete operating-temper-
ature range it compensates for the bridge
circuits temperature sensitivity. Together
with
R
2
and
R ,
R
1
forms one arm of the
bridge circuit, while the auxiliary resistor
R
3
and sensor resistor
R
S
form the other arm.
The difference in voltage between the two
arms is tapped off at the bridge diagonal
and used as the measurement signal.
The evaluation circuit is contained on a
second thick-film substrate. Both hybrids
are integrated in the plastic housing of the
plug-in sensor.
The hot-film air-mass meter is a thermal
flowmeter. The film resistors on the ceram-
ic substrate are exposed to the air mass
under measurement. For reasons asso-
ciated with flow, this sensor is far less
sensitive to contamination than, for
example, a hot-wire air-mass meter, and
there is no need for the ECU to incorporate
a self-cleaning burn-off function.
1
2
3
4
0
200
400
600
800 kg . h
-1
0
1
2
3
Output voltage
U
A
4
5
V
Mass rate of flow
Q
m
Characteristic curves.
R
3
R
2
R
T
R
1
R
H
+
-
+
-
1 2 3 4
R
S
R
5
C
4
U
k
Operating principle. B
A
Air-mass meters
55
1
2
3
4
5
6
Dimension drawings.
E Plug-in sensor, M Measurement venturi, S1/S2 Plug connection
Measure-
Plug-in
Ø A Ø B C
D
E
H
K
L
M
R
ment venturi connection Part number
60
66
70
73
86
33
75
130 82
37 KS
S1
0 280 217 102
70
76
50
69
82
34.8
96 42 KS
S1
0 280 217 107
70
76
70
69
82
33.5 85
130 92
42 KS
S2
0 280 217 120
80
86
70
73
86
39 130 KS
S2
0 280 217 519
95.6 102
70
76.2 91.2 45
110
130 117 54 Alu
S1
0 280 217 801
S1
S2
Plug-in sensor.
1 Sensor, 2 Hybrid, 3 Power module,
4 Mounting plate, 5 Heat sink, 6 Plug housing
R
T
R
1
R
S
R
H
G
S
H2
H1
T
Q
m
A
B
Sensor element with thick-film resistors.
Q
M
Mass rate of flow,
R
1
Trimmer resistor,
R
H
Heater resistor,
R
S
Sensor resistor,
R
T
Air-temperature measuring resistor,
A Front, B Rear
Installation instructions
Water and other liquids must not collect in
the measurement venturi. The
measurement venturi must therefore be
inclined by at least 5° relative to the
horizontal. Since care must be taken that
the intake air is free of dust, it is imperative
that an air filter is fitted.
Explanation of symbols:
R
1
Trimmer resistor
R
2
,
R
3
Auxiliary resistors
R
5
,
C
4
RC element
R
H
Heater resistor
R
S
Platinum metal-film resistor
R
T
Resistance of the air-temperature-
sensor resistor
U
K
Bridge supply voltage
U
A
Output voltage
U
V
Supply voltage
Connector-pin assignment
Pin 1 Ground
Pin 2
U
A
()
Pin 3
U
V
Pin 4
U
A
(+)
Accessories
For 0 280 217 102, .. 107, .. 801
Plug housing
1 284 485 118
Receptacle
1 284 477 121
1
)
Protective cap
1 280 703 023
1
)
Each 4-pole plug requires 1 plug housing,
4 receptacles, and 1 protective cap.
1
) Quantity 5 per package
For 0 280 217 120, .. 519
Desig-
For conductor Part number
nation
cross-section
Plug
housing 1 928 403 112
Contact
0.5...1.0 mm
2
1 987 280 103
pin
1.5...2.5 mm
2
1 987 280 105
Individual 0.5...1.0 mm
2
1 987 280 106
gasket
1.5...2.5 mm
2
1 987 280 107
Each 4-pole plug requires 1 plug housing,
4 contact pins, and 4 individual gaskets.
Note
For automotive applications, original AMP
crimping tools must be used.
E
D
20
L
5
±
0,3
22,3
±
0,3

M
E
S1
R
28
18
ø H
45
4,5
±
0,3
M
±
1
K
±
0,5
43
±
0,5
R 1
±
0,3
4 3 2 1
ø B
ø A
±
0,5
47
ø A
±
0,5
68
ø 22
C
4 3 2 1
øB
øA
±
0,4
47
øA
±
0,4
68
25
±
0,25
±
0,25
50
M6
±
0,2
38
C 56
Air-mass meters
A
B
Hot-film air-mass meter, Type HFM 5
Measurement of air-mass throughflow up to 1000 kg/h
Technical data / range
Nominal supply voltage U
N
14 V
Supply-voltage range U
V
8...17 V
Output voltage U
A
0...5 V
I
nput current I
V
< 0.1 A
Permissible vibration acceleration 150 ms
2
Time constant 63 1
) 15 ms
Time constant
2
) 30 ms
Temperature range
40...+120 °C
3
)
Part number
0 280 217 123
0 280 218 019
0 280 217 531
0 280 218 008
0 281 002 421
Measuring range Q
m
8...370 kg/h
10...480 kg/h
12...640 kg/h
12...850 kg/h
15...1000 kg/h
Accuracy
4
) 3% 3% 3% 3% 3%
Fitting length L
E
22 mm
22 mm
22 mm
16 mm
22 mm
Fitting length L
A
20 mm
20 mm
20 mm
16 mm
20 mm
I
nstallation length L
96 mm
96 mm
130 mm
100 mm
130 mm
Connection diam. D
60 mm
70 mm
80 mm
86/84 mm
6
)
92 mm
Venturi ID
50 mm
62 mm
71 mm
78 mm
82 mm
Pressure drop at
nominal air mass
5
) < 20 hPa
< 15 hPa
< 15 hPa
< 15 hPa
< 15 hPa
Temperature sensor
Yes
Yes
Yes
No
Yes
Version
1
2
3
4
5
1
) In case of sudden increase of the air-mass flow from 10 kg · h
1
auf 0,7 Q
m nominal
, time required to reach
63% of the final value of the air-mass signal.
2
) Period of time in case of a throughflow jump of the air mass | m/m
| 5%.
3
) For a short period up to +130 °C.
4
) | Q
m
/Q
m
|: The measurement deviation Q
m
from the exact value, referred to the measured value Q
m
.
5
) Measured between input and output
6
) Inflow/outflow end
Accessories
for connector
Plug housing
Contact pins
Individual gaskets
For conductor cross-section
1 928 403 836
1 987 280 103
1 987 280 106
0.5...1 mm
2
1 987 280 105
1 987 280 107
1.5...2.5 mm
2
Note: Each 5-pole plug requires 1 plug housing, 5 contact pins, and 5 individual gaskets.
For automotive applications, original AMP crimping tools must be used.
Application
In order to comply with the vehicle
emission limits demanded by law, it is
necessary to maintain a given air/fuel ratio
exactly.
This requires sensors which precisely
register the actual air-mass flow and output
a corresponding electrical signal to the
open and closed-loop control electronics.
Design
The micromechanical sensor element is
located in the plug-in sensors flow
passage. This plug-in sensor is suitable for
incorporating in the air filter or, using a
measurement venturi, in the air-intake
passages. There are different sizes of mea-
surement venturi available depending upon
the air throughflow. The micromechanical
measuring system uses a hybrid circuit,
and by evaluating the measuring data is
able to detect when return flow takes place
during air-flow pulsation.
Operating principle
The heated sensor element in the air-mass
meter dissipates heat to the incoming air.
The higher the air flow, the more heat is
dissipated. The resulting temperature differ-
ential is a measure for the air mass flowing
past the sensor.
An electronic hybrid circuit evaluates this
measuring data so that the air-flow quantity
can be measured precisely, and its
direction of flow.
Only part of the air-mass flow is registered
by the sensor element. The total air mass
flowing through the measuring tube is
determined by means of calibration, known
as the characteristic-curve definition.
Q
m
U
Compact design.
Low weight.
Rapid response.
Low power input.
Return-flow detection.
Application
In internal-combustion engines, this sensor
is used for measuring the air-mass flow
so that the injected fuel quantity can be
adapted to the presently required power, to
the air pressure, and to the air temperature.
Explanation of symbols
Q
m
Air-mass flow rate Q
m
Absolute accuracy Q
m
/
Q
m
Relative accuracy
Time until measuring error is 5% 63
Time until measured-value change
63% B
A
Air-mass meters
57
1
2
3
4
5 u