Reversal margin
The reversal range (also known as hysteresis , in the case of mechanical measuring devices also called measurement reversal range ) is generally the difference between the positions at the end of two mechanical positioning movements at the same target location if these movements have occurred from different directions.
The reversal span of a mechanical measuring device is the difference between the displays for the same measured value , depending on whether the measured value has risen or fallen there before.
Mechanical play and / or friction are responsible for the reversal margin .
Measurement reversal margin
The DIN standard 1319 defines the reversal range as the difference in the displays that are obtained for the same value of the measured variable , if the brand of the measuring device, starting from smaller and once from larger values, adjusts itself continuously or gradually.
In the calibration of precision indicators with mechanical display needs for accurate measurements often the measured value hysteresis are determined.
The measurement reversal margin is one of the causes of measurement errors in mechanical measuring instruments with pointer.
example
A pointer voltmeter measures any voltage that is greater than 1 volt . The voltage slowly drops to 1 volt and then remains constant. However, the voltmeter display remains at 1.1 volts. With another measurement, the voltage rises to 1 volt and then remains constant. Now the voltmeter shows only 0.95 volts. The measurement reversal range is 0.15 volts (difference between 1.1 and 0.95 volts).
The pointer always “sticks” a little too early when making changes, when the corrective force no longer exceeds the static friction . It therefore occurs only for encoders with friction or with play elements, but not for example moving coil instruments with strap storage on.
Reversal margin for mechanical actuators
A reversal margin also occurs with other mechanical, backlash or friction arrangements:
- for actuators of the feed movement z. B. of turning , grinding and milling machines
- with pneumatic and hydraulic drives (e.g. a pneumatic cylinder working against a spring force )
The backlash of a steering is called steering play .
swell
- ^ Basics of measurement technology, Paul Profos, 5th, revised edition, R. Oldenbourg Verlag Munich Vienna 1997, page 21 "( ISBN 3-486-24148-6 )
- ↑ Guideline DKD-R 4-3 - Calibration of measuring equipment for geometrical measured quantities ( Memento of the original from November 29, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
