KELAG Künzli Elektronik AG KAS901-01A Instructions for use

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Ringstrasse 5 Fax [phone]
Ch-8630 Schwerzenbach E-Mail [email protected]
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Application manual
Acceleration, inclination and vibration sensor KAS901- (KAS903-) series
Contents
1. Applications ..............................................................................................................................................................2
1.1 Tilt and levelling applications ..............................................................................................................................2
1.2 Inclination and angle measuring .........................................................................................................................2
1.3 Acceleration measuring ......................................................................................................................................2
1.4 Vibration measuring ............................................................................................................................................2
2 Characteristics / Technology .....................................................................................................................................2
2.1 Shock resistance of the sensing element ...........................................................................................................2
2.2 Repeatability and long term stability ...................................................................................................................2
2.3 Resolution ...........................................................................................................................................................3
2.4 Reduced sensitivity to vibrations thanks to gas attenuation ...............................................................................3
2.5 Structure of the sensing element ........................................................................................................................3
2.6 Functional principle .............................................................................................................................................3
3 Mechanical mounting.................................................................................................................................................4
3.1 Alignment for inclination measuring....................................................................................................................4
3.1.1: Possibelity 1 ................................................................................................................................................4
3.1.2: Possibility 2:.................................................................................................................................................4
3.1.3: Mounting and output....................................................................................................................................4
3.2 Mounting for acceleration and vibration..............................................................................................................5
3.3 Offset-Alignment .................................................................................................................................................5
3.4 Temperature compensation................................................................................................................................6
3.5. Inclination in relation to earth gravity g ..............................................................................................................6

KELAG Künzli Elektronik AG Telefon [phone]
Ringstrasse 5 Fax [phone]
Ch-8630 Schwerzenbach E-Mail [email protected]
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1. Applications
Typical applications for the KAS series sensors are:
- inclination limiter (tilt sensor)
- levelling
- inclination
- acceleration
- vibration
Depending on the intended use the best suitable type must be selected. Please contact our product specialists for
information. Phone: [phone].
1.1 Tilt and levelling applications
Typical applications can be tilt limiters, levelling of machinery, apparatuses or measuring equipment, automatic
levelling of jibs / booms, excavator shovels, platforms etc.
1.2 Inclination and angle measuring
Examples: inclination measuring in measuring equipment like lasers, in vehicles, robots, surgical operation tables,
building and production machinery
1.3 Acceleration measuring
Applications such as shock and crash monitoring, movement monitoring and recording for fitness analysis or
elderly / handicapped persons combined with alert systems, free fall detection, automobile equipment as ESP
(electronic stabilising program) and ABS (anti blocking system).
1.4 Vibration measuring
Applications are for example bearing damage monitoring, Baby monitoring system, theft protection, earth quake
safety switch-off devices.
2 Characteristics / Technology
2.1 Shock resistance of the sensing element
The sensing elements based on capacitive measuring principle feature high precision and high shock resistance,
resulting from the particular 3D micromechanics technology made of high purity silicon. Thanks to the optimized
structure, no drifts caused by deformation must be expected, even after severe shocks.
2.2 Repeatability and long term stability
With SCA61T for instance repeatability up to 0,01° or 0,2mg and long term stabilities of the same order can be
achieved. The hysteresis (e.g. 0,02°) caused by quick temperature changes degenerates to zero within a short
time.

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2.3 Resolution
The sensing elements formed by a dual capacitor produce extremely low noise levels and a high output signal. The
major part of the noise is caused by the signal conditioning circuitry. Resolutions in the order of 0,001°or 7µg/√Hz
(KAS901-4x) are possible.
2.4 Reduced sensitivity to vibrations thanks to gas attenuation
Influences by vibrations may interfere with inclination measuring. The gas attenuation in the sensing element filters
a good part of such interferences and in addition helps avoid overshooting of the sensing pendulum. Additional
resonance frequencies are completely damped. For inclination sensors the influence of vibrations is reduced, for
vibration sensors the sensor’s natural resonance is damped. This means that the appropriate sensor type must be
selected for each application.
2.5 Structure of the sensing element
2.6 Functional principle
The pendulum with the measuring mass is moved in the measuring direction by a force (acceleration, inclination,
vibration) acting in this direction. The movement of the measuring mass causes a change of capacitance which is
registered as primary measuring signal. The output signal (0,5 .. 4,5V) is proportional to the deflection, thus to the
acceleration. For inclination measuring the conversion from g = 9.81 m/s2into angular degrees is a sine function. A
sensor with small measuring range (+/-0,5g) has a higher resolution than a sensor with large (+/-12g) measuring
range.
Measuring principle and alignment (e.g. for acceleration / shocks)
Silicon wafer
with metal film
(capacitor)
Pendulum with
measuring mass
Silicon wafer
with metal
film
(capacitor)
Measuring
direction
2,9mm
1.95m

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3 Mechanical mounting
The housings are marked with a symbol indicating the measuring direction.
3.1 Alignment for inclination measuring
3.1.1: Possibelity 1
3.1.2: Possibility 2:
3.1.3: Mounting and output
Example 1:
+1g 

+90°Position 

4,5V 0g 

0°Position 

2,5V -1g 

-90°Position 

0,5V
+1g Position 0g Position -1g Position
axis
of rotation
rotation
rotation
axis of rotation
Base Plate
0°angle
position

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Ch-8630 Schwerzenbach E-Mail [email protected]
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Example 2:
The pictures describe how the tilt is and what sort of output (direction) has to be expected.
X-axis: 3.14 V >2.5V 1.81 V >2.5V
Y-axis: 3.16 V >2.5V 1.82V <2.5V
3.2 Mounting for acceleration and vibration
3.3 Offset-Alignment
Caused by the integration into the application a mechanical offset between the sensor and the application may
occur. For precise measuring we recommend an offset alignment at the position 0g 0°2,5V. The alignment
will be done in the application device by matching the offset voltage. Thus the absolute precision increases
considerably.
The sensing direction is indicated
by a symbol on the housing
Direction of acceleration
(X-axis)

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Aidditionaly we offer a an additional 0-point calibration. Then the mounting has to be so, that the “potting” side is on
the upper side. For that we offer an additional cap. Please contact our local sales representative or factory.
(see also chapter 3.4 Temperature compensation)
3.4 Temperature compensation
Due to shrinking / dilatation of the sensing element at temperature variations the geometry of the element slightly
varies. This will have an effect on the result of the measurement. Due to the symmetrical shape of the sensing
element, most of this effect is automatically compensated. The remaining drift caused by temperature variation is
very low, but should be compensated additionally for high precision applications.
Methods:
- applying temperature compensated sensors of the KAS901-01A, KAS901-02A, KAS901-5x, KAS901-4x
and KAS903-Serie
- for the temperature compensated sensors calibration data is available on demand, stating the remaining
temperature sensitivity after compensation. These data may be used for external correction algorithms. In addition
the built-in temperature sensor in the SCA61T, SCA100T and SCA103T series may be used.
- For information please contact our technical consultants by phoning: [phone].
3.5. Inclination in relation to earth gravity g
[+°];
-45°
+45°
+90°
-90°
[+G]
[-G]
[-°];
[4mA]
1G-Sensor: ±1G - ±90°
[12mA]
-1G +1G
[+°];
-30°
[+G]
[-G]
[-°]
0.5G-Sensor: ±0.5G = ±30°
+30°
+0.5G
[20mA]
[4mA]
-15°
+15°
-0.5G
[+°];
[-°]