The measurement technique is concerned with devices and methods for determining ( measuring ) physical parameters such as length , mass , force , pressure , electric current , temperature or time . Important sub-areas of measurement technology are the development of measurement systems and measurement methods as well as the acquisition, modeling and reduction (correction) of measurement deviations and undesirable influences . This also includes the adjustment and calibration of measuring devices and the correct reduction of measurements to uniform conditions.
Measurement technology, in conjunction with control and regulation technology, is a prerequisite for automation technology . The term production metrology is known for the methods and products of industrial production .
The measurement technology can be divided into different types of procedure for a measurement (measurement methods).
Deflection method, zero balance method and competing
With the deflection measuring method , the measured value is determined from the deflection or another display on a measuring device.
- Example: Spring balance with scale labeling in grams.
- With this method, the balance must be adjusted.
With the zero adjustment or compensation measurement method , a known variable is set so that the difference with the variable to be measured results in the value zero.
- Example: Beam balance with display for torque balance.
- This method uses a set of weights or sliding weights.
- Modifications of these basic forms; Examples
In the comparison or substitution measurement method , the display of the variable to be measured (which is unsuitable for quantitative evaluation) is simulated by a display of the same size using an adjustable known variable.
- Example: Spring scale with scale labeling in millimeters.
- This method requires a set of weights to be available for the scale.
In the case of the difference measurement method , the difference between it and a comparison variable is determined instead of the variable to be measured.
- Example: Beam balance with scale (more than just a zero point display).
- With this method, a deflection arises with which small changes in a size can be measured much more precisely than by calculating the difference after measuring the size itself.
With the integrating measuring method , the variable to be measured is obtained from instantaneous values by integration (depending on the technology also by summation or counting), preferably over time.
- Example: counter for distance measurement that records the revolutions of a wheel.
- With this method, reliable information can be obtained even with strong fluctuations (in the example in the speed ).
Analog or digital method
See also the article on digital measurement technology for a comparison of the methods
Direct or indirect method
Direct measurement technology
With the direct measurement method , the measured variable is compared directly with a scale or standard . Examples of a direct measurement are the application of a scale to the length to be determined or the direct comparison of an electrical voltage to be measured with an adjustable reference voltage on a voltage compensator .
Indirect measurement technology
Measurement systems and indirect measurement methods make quantities measurable even if they are not directly accessible. Another variable is measured and the measured variable is determined from it if there is a known, clear relationship between the two based on a measurement principle . For example, the distance between the earth and the moon could never be determined by direct comparison with a yardstick. Using the transit time of light or radio waves, however, has been successful for 30 years (today it is accurate to within a few millimeters).
A very old method of indirect distance measurement , with which the radius of the lunar orbit can also be determined, is triangulation . The angle at which a third point can be seen is determined from two points of view with a known distance. The distance to the third point can be calculated from the two angles and the known distance. Similarly, the distance from the moon can be determined by indirect comparison with a relatively short scale.
The majority of the measurement methods used in everyday life, science or industry use indirect methods. This also underlines the importance of understanding measurement deviations and their propagation through multi-level measurement systems (see also compensation calculation and variance analysis ).
So-called simultaneous measurements can be used as a variant or extension of the indirect measurement methods . In many areas of science and technology, simultaneous measurements are made from different points. The purpose is the elimination of time errors , the minimization of the measurement deviation or the detection of sources of systematic measurement errors.
Basics of electrical measurement technology
The following should be mentioned in more detail on the above topics:
- Time dependence of measured quantities
- constant or their (slow) change measurable variables
- as a single measured value, sequence of measured values, line diagram
- Instantaneous values of rapidly changing, preferably periodic quantities
- Quantities that can be determined by averaging
- constant or their (slow) change measurable variables
- Electromechanical indicating measuring devices
- Digital electronic indicating measuring devices
- Registering measuring devices
- Matching gauges
- Measurement method
Types of measuring devices
A detailed list of measuring devices can be found in the article measuring device .
An overview of how a chain of measuring devices of different types leads to the measured value you are looking for can be found in the article Measuring device .
Classification according to physical quantities
- Pressure → pressure gauge , strain gauge , barometer - Pa, bar
- Flow → flow meter , flow sensor - m³ / s, l / min, kg / s
- Electrical voltage → voltmeter - V
- Electric current → ammeter - A
- Frequency → frequency meter , frequency counter - Hz
- Speed → speed measurement , tachometer - m / s
- Force → force measurement , force transducer - N
- Length / distance / depth → distance measurement , displacement sensor - m
- → temperature thermometers , resistance thermometers , thermocouples - K, ° C, ° F
For other sizes see list of measuring devices
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- Werner Richter : Electrical measurement technology - basics. Verlag Technik, Berlin, VDE-Verlag, Offenbach 1994 (3rd edition).
- Werner Kriesel, Hans Rohr, Andreas Koch: History and future of measurement and automation technology. VDI-Verlag, Düsseldorf 1995. ISBN 3-18-150047-X .
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- Jörg Hoffmann: Pocket book of measurement technology. Fachbuchverlag, Leipzig 2007 (5th edition). ISBN 978-3-446-40993-4
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