Transverse anchor sensor

Transverse anchor sensor

The transverse anchor sensor is an electrical sensor for measuring path lengths. In a magnetic circuit with iron, the moving element of the sensor changes the air gap. This changes the magnetic resistance and the inductance L of the coil. Neglecting scattering losses and set µ _r (air) = 1, the following applies:

${\displaystyle L(s)={\frac {\mu _{0}\cdot N^{2}\cdot A}{{\frac {l_{Fe}}{\mu _{r}}}+2\cdot s}}}$

At the path length s = 0 the movable element touches the iron circle. Furthermore, l _{Fe is} the average length of the iron circle with cross section A , µ _{0 is} the magnetic field constant , µ _{r is} the relative permeability of the iron and N is the number of turns of the coil.

Differential transverse anchor sensor

The characteristic is not linear. The output signal can be linearized with a differential connection of two encoders to a differential transverse armature encoder and evaluation in a Wheatstone bridge circuit .

${\displaystyle L_{1}(s)={\frac {\mu _{0}\cdot N^{2}\cdot A}{{\frac {l_{Fe}}{\mu _{r}}}+2\cdot (s_{0}{\color {red}+}s)}}}$

${\displaystyle L_{2}(s)={\frac {\mu _{0}\cdot N^{2}\cdot A}{{\frac {l_{Fe}}{\mu _{r}}}+2\cdot (s_{0}{\color {red}-}s)}}}$

Here, the path length s = 0 means the central position and s _{0 means} the air gap in the central position. The moving element can also be the measuring object directly if it is ferromagnetic. Then the sensor works without contact.

The measuring paths are approx. 0.4 ... 0.7 mm. It is used to measure lever positions, to measure the displacement of e.g. B. in waves of power plant turbines, as a converter in the strain, force and acceleration measurement.

Individual evidence

1. ↑ Manfred Weck, Christian Brecher : Machine tools 5: Metrological investigation and assessment, Dynamic stability , Springer, 2006, p. 18f, ISBN 978-3-540-22505-8 ( limited preview in the Google book search)

See also

• Displacement sensor