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Knowledge of tachometer
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What was a tachometer?
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How does a tachometer work?
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What are the tachometer used for?
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Which tachometer are available from Conrad?
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FAQ – Frequently Asked Questions about Tachometers
What was a tachometer?
A tachometer is a mechanical or electronic measuring device that determines the number of revolutions per time unit of rotating elements. A unique circular motion of the rotating object in a full circle of 360 degrees is considered a revolution. A tachometer evaluates the revolutions per time unit and outputs them as analogue scale value or as digital number.
"Revolutions per minute" (min -1 ) and "revolutions per second" (s -1 ) have established themselves as common units of measurement. The abbreviations "UpM" and "rpm" are also commonly used. The scientifically correct designation of the speed according to the SI unit system "1/s" (corresponds to s -1 ) is hardly used.
How does a tachometer work?
The following principles must be distinguished in the function of tachometer:
Mechanical speed measurement
This type of measurement uses the centrifugal force of moving masses. The higher the speed, the greater the noise t, with which the moving mass is aimed away from the axis. This movement is output via a lever mechanism to a pointer over a scale. This measuring method requires a direct mechanical contact between the object to be measured and the measuring device. This is realized with measuring tips, hollow tips, extension shafts and/or measuring wheels.
Electrical speed measurement
Here, a magnet rotates in an electrical coil in which a voltage is induced. Their height increases with the speed so that this value can be evaluated. The rotational movement must also be transmitted by a mechanical connection between the rotating part and the measuring device.
Electronic speed measurement
There are various technical solutions in this area, but all of them are based on the fact that a light beam (different generation, strength and wavelength) is interrupted. The number of revolutions is determined from the interruptions per time unit . Another possibility is that the frequency of reflections of a reflective element applied to the rotating part is counted. The measurement can be carried out by means of mechanical contact or contact-free, for example by beam-on with a laser beam.
Stroboscope measurement
In this measuring method, the object to be measured may be marked with additional markings. To measure it, we illuminate it with extremely bright flashes of light at a defined flash frequency. If the flash frequency and speed match, the object to be measured appears as standing. It should be noted that this effect also occurs with even-numbered dividers or multiples of the speed. Xenon lamps or high-power LEDs are used to generate the light flashes. The stroboscopes usually require an external trigger for defined control. Flash frequencies of up to 120,000 flashes per minute can be reached. Devices with this measuring function are also available handy small stroboscopes .
Key features
The possibility of measuring rotating processes provides further evaluation options with simple tools. For example, the conveyor speed of conveyor belts – hence their length – is called, whereby the tachometer is supplemented by a measuring wheel that rests on the belt.
Digital devices output numerical values on displays, have memory for medium, maximum and minimum values as well as the last measured value. Accessories such as reflective measuring marks are often included.
What are the tachometer used for?
The range of possible applications ranges from tachometer in cars to monitoring and maintenance of rotating parts in many industries, for example in print shops, compressor stations of the oil and natural gas industry as well as the measurement of a record player.
Which tachometer are available from Conrad?
The Conrad online shop offers high-quality mechanical and electronic tachometer as well as stroboscope systems with different power output.
The price range of the products offered ranges from two to four digits. DAkkS, ISO and factory standard are available as selection characteristics "Calibration".
Some of the manuals and data sheets are available for download. In addition, you will receive recommendations for useful accessories from the respective product, which you can also purchase at Conrad.
FAQ – Frequently Asked Questions about Tachometers
What was to be observed when handling rev knives?
- Tach meters are precision measuring instruments and should be handled with care. Use the original packaging for transport and storage. Store the devices in a dry place; dripping and splashing water must be strictly avoided.
- Measurements on moving, vibrating and rotating parts can be accompanied by serious health hazards. Always follow the operating instructions of the respective device exactly and make sure that the operating instructions are always available.
- Moving objects in the stroboscope light appear standing or in slow motion. The objects must never be touched.
- The light from stroboscope lamps can cause epileptic seizures in persons at risk.
- The electronic components of the device contain substances that are harmful to the environment. They must be disposed of in accordance with the applicable environmental guidelines
- Calibration may be required for certain applications.
- Electronic interference can affect measurement results of electronic devices.
- Clean the tachometer thoroughly after each use.
- Do not open the tachometer unless the battery compartments are to be replaced. The warranty will be void in the event of improper use, attempts to repair or opening. Have repairs carried out by the manufacturer or supplier.
How long does a tachometer last?
The service life of purely mechanical tach is theoretically unlimited. The same applies to digital devices, whereby the batteries have to be replaced from time to time.
How can ich detect defective tachometer?
- Implausible measured values indicate a defective device or interfering ambient influences.
- A missing display in most cases indicates that the power supply is not working, was usually remedied by replacing the batteries.
- A blurred display may be due to the fact that the protective film is still on the display.