Ratiometric

The term ratiometric is made up of ratio , Latin for ratio, and metric , Greek for measurement. In electronics it means that an unknown quantity can be derived from the ratio of several known other quantities to one another.

General examples

Setup for ratiometric measurement

In general, with a ratiometric measurement, the quotient of two variables with the same interference superposition shows that this does not affect the measurement. For example, a ratiometric quantity is independent of the supply voltage.

The drawing shows using the example that the ratio of the measured voltages U ₁ and U ₂ at the resistors R ₁ and R _{2 is} independent of the absolute value of the supply voltage U _source . Thus, if the value for R _{1 is} known, the resistance ratio or R ₂ can be inferred by measuring the voltage ratio .

${\displaystyle {\frac {R_{1}}{R_{2}}}={\frac {U_{1}}{U_{2}}}\Leftrightarrow R_{1}=R_{2}\cdot {\frac {U_{1}}{U_{2}}}}$

Example: If the supply voltage of a potentiometer increases , the voltage on the sliding contact also increases proportionally , but the ratio of the supply voltage to the drawn voltage remains the same.

application

Ratiometric measurements are often recorded when sensors are used in combination with A / D converters . Such measures to reduce interference are necessary in modern vehicle electronics in particular.

On the other hand, quotient measuring mechanisms for engine temperature or fuel gauge are outdated .

source

• Rupert Patzelt, Herbert Schweinzer: Electrical measurement technology . 2nd Edition. Springer-Verlag, Vienna 1996, ISBN 978-3-211-82873-1 , p. 319 .