22 Acceleration sensors A B

Piezoelectric vibration sensorsMeasurement of structure-borne noise/acceleration

Technical data

Frequency range 1...20 kHzMeasuring range ≈ 0.1...400 g 1)Sensitivity at 5 kHz 26 ±8 mV/gLinearity between 5...15 kHz

at resonances +20/–10 % of 5 kHz-value (15...41 mV/g)Dominant resonant frequency > 25 kHzSelf-impedance > 1 MΩCapacitance range 800...1400 pFTemperature dependence

of the sensitivity ≤ 0.06 mV/(g · °C)Operating-temperature range:

Type 0 261 231 118 –40...+150 °CType 0 261 231 148 –40...+150 °CType 0 261 231 153 –40...+130 °C

Permissible oscillations Sustained ≤ 80 gShort-term ≤ 400 g

InstallationFastening screw Grey cast iron M 8 x 25; quality 8.8

Aluminum M 8 x 30; quality 8.8Tightening torque (oiled permitted) 20 ±5 N · mMounting position Arbitrary1) Acceleration due to gravity g = 9.81 m · s–2.Resistant to saline fog and industrial climate.

ApplicationsVibration sensors of this type are suitable forthe detection of structure-borne acousticoscillations as can occur for example in caseof irregular combustion in engines and onmachines. Thanks to their ruggedness,these vibration sensors can be used evenunder the most severe operating conditions.

Areas of application– Knock control for internal-combustion

engines– Protection of machine tools– Detection of cavitation– Monitoring of bearings– Theft-deterrent systems

Design and functionOn account of its inertia, a mass exertscompressive forces on a ring-shapedpiezo-ceramic element in time with theoscillation which generates the excitation.Within the ceramic element, these forcesresult in charge transfer within the ceramicand a voltage is generated between the top and bottom of the ceramic element.This voltage is picked-off using contactdiscs – in many cases it is filtered andintegrated – and made available as ameasur-ing signal. In order to route thevibration directly into the sensor, vibrationsensors are securely bolted to the objecton which measurements take place.

Measurement sensitivityEvery vibration sensor has its own individualresponse characteristic which is closelylinked to its measurement sensitivity. Themeasurement sensitivity is defined as theoutput voltage per unit of acceleration dueto gravity (see characteristic curve). Theproduction-related sensitivity scatter isacceptable for applications where theprimary task is to record that vibration isoccurring, and not so much to measure itsseverity. The low voltages generated by the sensorcan be evaluated using a high-impedanceAC amplifier.

aU

Reliable detection ofstructure-borne noise forprotecting machines andengines. Piezo-ceramic with highdegree of measurementsensitivity. Sturdy compact design.

Range

Vibration sensor2-pole without cable 0 261 231 1482-pole, with cable, length 480 mm, up to +130 °C 0 261 231 1533-pole, with cable, length 410 mm, up to +150 °C 0 261 231 118

Accessories

Sensor Plug housing Contact pins Individual gasket For cablecross section

0 261 231 148 1 928 403 137 1 987 280 103 1 987 280 106 0.5...1.0 mm2

1 987 280 105 1 987 280 107 1.5...2.5 mm2

0 261 231 153 1 928 403 826 1 928 498 060 1 928 300 599 0.5...1.0 mm2

1 928 498 061 1 928 300 600 1.5...2.5 mm2

0 261 231 118 1 928 403 110 1 987 280 103 1 987 280 106 0.5...1.0 mm2

1 987 280 105 1 987 280 107 1.5...2.5 mm2

Note: A 3-pole plug requires 1 plug housing, 3 contact pins, and 3 individual gaskets. In automotive applications, original AMP crimping tools must be used.

EvaluationThe sensor’s signals can be evaluatedusing an electronic module. This is described on Pages 26/27.

Installation instructionsThe sensor’s metal surfaces must makedirect contact. No washers of any type areto be used when fastening the sensors.The mounting-hole contact surface shouldbe of high quality to ensure low-resonancesensor coupling at the measuring point.The sensor cable is to be laid such thatthere is no possibility of sympatheticoscillations being generated. The sensormust not come into contact with liquids forlonger periods.

Explanation of symbolsE Sensitivityf Frequencyg Acceleration due to gravity

Connector-pin assignmentsPin 1, 2 Measuring signalPin 3 Shield, dummy

B A Acceleration sensors 23

V

7FF

1 2 3 4 5 6

Vibration sensor (design).1 Seismic mass with compressive forces F,2 Housing, 3 Piezo-ceramic,4 Screw, 5 Contact, 6 Electrical connection, 7 Machine block, V Vibration.

a

ø5

±0,2

±0,2

ø4,

55

52,2 ±2

27

8,4±0

,15

+0,3-0,111,65

18

ø13

ø22

20°

24±1

,5

27

8,4

13

±0,2

1828

8,4

13

ø20

41,1 ±1

32,1 ±1

L

L

18

±0,2

0,4

±132

ø20

+0,3-0,111,65

Pin 1

Pin 1

Pin 2

Pin 3

Pin 2

±0,2

a

a

Frequency f5 10 15 kHz

0

10

20

30

mV g-1.

Sen

sitiv

ity E

Response characteristic as a function of frequency.

0,05

0,05

M8

22

RZ16

A

A

Mounting hole.

Dimension drawings.a Contact surface.

0 261 231 148

0 261 231 118

0 261 231 153

Part Lnumber mm

.. 118 410 ±10

.. 153 430 ±10