Compensator (measurement technology)

A compensator as a measuring device works according to the measuring method of compensation . The variable to be measured is compared with a compensation variable. This variable is physically identical, adjustable and its value can be determined. It is readjusted until equality is determined (comparison to zero difference). The value of the compensation variable often provides the measured value directly ; occasionally a correction factor has to be included.

A clear example of compensation in measurement technology is the beam balance with the setting of a torque balance and, with lever arms of the same length, also a mass balance.

Conventional electrical compensator

The term compensator has become particularly important in electrical measurement technology. Compared to electromechanical voltage and current measuring devices , one advantage of the compensator is the significantly smaller error limits that can be achieved . Another advantage lies in the fact that the measurement is not falsified by feedback (internal consumption) during adjustment .

• The stress compensator is dealt with under its own heading. The measuring circuit does not draw any current from the device under test during calibration.

Circuit of a current compensator

• The current compensator is shown opposite. During the adjustment, the measuring circuit does not take any voltage from the measurement object. The current compensator works like a voltage compensator by means of measuring resistors .

To measure , use to set that . This must be. Then applies ${\displaystyle I_{x}}$ ${\displaystyle I_{0}}$ ${\displaystyle R_{2}}$ ${\displaystyle U_{1}=U_{3}}$ ${\displaystyle I_{0}>I_{x}}$

${\displaystyle U_{3}=I_{x}\cdot R_{3}}$

${\displaystyle U_{1}=(I_{0}-I_{x})\cdot R_{1}}$

${\displaystyle I_{x}=I_{0}{\frac {R_{1}}{R_{1}+R_{3}}}}$

• As voltage compensators further operate the Wheatstone bridge for the measurement of DC resistance and the AC voltage bridge for measuring alternating current resistance .

Electronic compensator

Example of a feedback measuring circuit:
Current-voltage converter

Every negative feedback measuring circuit can be understood as a compensator. In the example opposite, an electrical current is measured by building up an electrical voltage at the output of an operational amplifier , which generates a negative output voltage with a positive input current; this sends a current to the input current via the feedback resistor, just big enough that and become. This means that there is no adulteration through personal consumption ${\displaystyle I_{e}}$ ${\displaystyle U_{a}}$ ${\displaystyle R_{r}}$ ${\displaystyle I_{N}\to 0}$ ${\displaystyle U_{d}\to 0}$

${\displaystyle U_{a}=-\,I_{e}\cdot R_{r}}$

An analog-to-digital converter in the frequently used serial converter version also works like a compensator. Here, a digitally generated voltage is compared at regular intervals with the voltage to be measured and readjusted to this (except for the unavoidable quantization deviation ).

See also

• Compensation (technology)
• Compensator (geodesy)