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rpm measuring technology

Measuring methods

Data acquisition via mechanicalmeasuring sensors is the oldestway to measure rpm. Therevolutions in the sensor areelectronically analysed in theinstrument. This method is stillused frequently but mostly for lowrevolutions between 20 and 20,000rpm.

2. Electrical method using reflections (optical rpm measurement)

1. Mechanical rpm measurement

Measuring ranges of the different measuring procedures

3. rpm measurement using the stroboscopic method

It is not necessary to attachreflective tapes to the objects beingmeasured. For example, productionprocesses do not need to beinterrupted. Measuring range: 100to 20,000 rpm. In addition to rpmmeasurement the stroboscopicmeasuring method can also analyseoscillations and monitor motione.g. in moving diaphragms,loudspeakers etc.

The measuring methods in rpm measurement can be divided into 3 maingroups:

The disadvantages of thismeasuring method are thenonconstant load movementsduring measurement which dependlargely on the contact pressure. Inaddition, mechanical rpmmeasurement cannot be used forsmall objects. If the revolutions are too high slipmay occur.

The rotation is transmitted to themeasuring instrument via an infra-red light beam coming from theinstrument which is then reflectedby a reflective tape on the object.Please note that the maximumdistance between reflective tape and

instrument should not be exceeded(distance max. = 350 mm). This method is superior tomechanical rpm measurement.However, it is not always possibleto fix reflective tapes.

According to the stroboscopicprinciple, objects are stationary inthe eyes of the observer when thefrequency of the high-speed flashesis in synchronisation with the rpm(movement) of the object.Thestroboscope principle has clearadvantages over other measuringmethods using mechanical oroptical sensors: Using this methodit is possible to measure the rpm ofvery small objects or ininaccessible places.

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Note: testo 465 measures optically, testo 470 includes mechanical andoptical measuring methods, testo 475 includes mechanical andstroboscopic measuring methods

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Speed and length can be measuredusing a surface speed disc and asuitable measuring instrument. The running wheel is simply placedon the moving object (e.g.conveyor belt etc.) and the readingcan be taken. (Note: do not put toomuch pressure on the surfacespeed disc, press lightly).

The testo 475 mini stroboscopefunctions according to thestroboscopic measuring principle.By using the flashlight transmitteras a data sensor, oscillationmeasurements and motionmonitoring are possible in additionto rpm measurement.

Measuring speed and length

testo 475

rpm measuring technology

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