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What Is The Principle Of Step Tester Measurement?

The Step Tester belongs to the contact surface topography measuring instrument. According to the use of different sensors, contact step measurement can be divided into inductive, piezoelectric and photoelectric type 3.

The measurement principle is: when the stylus along the measured surface gently slide, because the surface has a small peak and valley so that the needle in the sliding

At the same time, also along the peak valley for up and down movement. The movement of the stylus reflects the surface profile. The electrical signal output by the sensor is measured after the bridge, the output is proportional to the displacement of the stylus from the equilibrium position. After amplification and phase-sensitive rectification, the displacement signal can be demodulated from the amplitude modulation signal, get amplified and the needle displacement is proportional to the slow change signal. And then by the noise filter, wave filter to further filter the modulation frequency and external interference signal and wave and other factors on the roughness measurement.

Inductance displacement sensor as a sensitive element, high precision, high signal to noise ratio, but the circuit is complex; piezoelectric displacement sensor for the piezoelectric crystal, its high sensitivity, simple structure, but the sensor low frequency response is not good, And easy to leakage caused by measurement error; photoelectricity is the use of photovoltaic components to receive through the slit of the luminous flux changes to detect changes in displacement.


Step Tester measurement accuracy is high, range, measurement results stable and reliable, good repeatability, in addition it can also be used as other topography measurement technology comparison. But also has its difficult to overcome the shortcomings:

1 due to contact between the probe and the measurement of the probe caused by deformation and wear, so that after the use of equipment in a period of time to reduce the accuracy of measurement;

2 probe in order to ensure wear resistance and rigidity can not be done very small sharp, if the probe head radius of curvature greater than the surface of the micro-pit on the surface of the radius of the measurement data will inevitably lead to deviation;

3 In order to make the probe not wear quickly, the hardness of the probe is generally high, so not suitable for precision parts and soft surface measurement.

Tongfang Health Technology (Beijing) Co.,Ltd