Piezoelectric force sensors – Piezoelectric ring force transducers for tensile and compression forces from

20 kN to 700 kN, Types 9101C, 9102C, 9103C, 9104C, 9105C, 9106C, 9107C

Page 4/6

© 2020 ... 2021 Kistler Group,

Eulachstrasse 22, 8408 Winterthur, Switzerland

Tel. +41 52 224 11 11, info@kistler.com, www.kistler.com. Kistler Group products are

protected by various intellectual property rights. For more details visit www.kistler.com

This information corresponds to the current state of knowledge. Kistler reserves

the right to make technical changes. Liability for consequential damage resulting

from the use of Kistler products is excluded.

Bending moment

Bending moments MB (Mx + My) increase the stress on one

side of the sensor and decrease it on the other. This results in

an uneven distribution of the axial force on the sensor, that can

distort the measuring results.

In extreme cases, this can lead to a one-sided overload of the

sensor or loss of the frictional connection, which can destroy

the structure or cause it to slip. It ultimately depends on the

applied axial force Fz which of the two cases occurs first in the

event of an impermissible bending moment.

Fig. 4:

Bending moment as a function of the axial force Fz

Bending moment graph

Attention

Lateral loads Fx,y and/or a torque Mz further reduce the

measuring range. In case of tight safety margins regarding

bending moments and suspected lateral loads or torque,

better get in touch with our local sales.

Example

A piezo sensor Type 9103C... is preloaded with Fv = 28 kN.

What bending moment can be tolerated for process forces in

the range Fp = 0 ... 33 kN?

We use a normalized formula to calculate the allowable

bending moment.

MB[%] ≤ 100% - 2x

|50%-Fz[%]|

Fz is the total axial force on the sensor, so the sum of the

preload Fv and the process force Fp.

The allowed bending moment depends on the applied total

force Fz and reaches its peak at 50  kN, half the nominal

axial force. In this case, when the process force is at 22 kN

(28 kN+22 kN = 50 kN).

If the force curve in the process is not known, the lowest value

is defined as the maximum load: 122.6 Nm.

Fv[%] = 28 kN

100 kN

= 28%

Fp[%] =

0 kN

100 kN

...

33 kN

100 kN

= 0 ... 33%

Fz[%] = Fv[%] + Fp[%] = 28 ... 61%

MB[28%] = 100% - 2 x

|50% - 28%| = 56%

≙122.6Nm

MB[61%] = 100% - 2 x

|50% - 61%| = 78%

≙170.8Nm

Tensile forces

Tensile forces are only applicable as long as the preload is

higher than the negative force: they reduce the (pre)load on

the sensor, which can be measured accordingly.

Fig. 5: maximum bending moment depending on preload and process

force

Fig. 3:

Bending moment