Potentiometer measurement

The potentiometer should be supplied with the integrated power supply unit (max. 5 V, configurable). The slider voltage is then measured relative to the supply voltage and output in %. Technical, the measurement is similar to a strain gauge half bridge.

Potentiometers from 1 kΩ can be used.


Measurement mode

Potentiometer (3/5-wire)

Operation mode

The supply voltage is configurable via CoE,
0.5...5 V

Measuring range, nominal

-1 … 1 V/V

Measuring range, end value (FSV)

1 V/V

Measuring range, technically usable

-1 …1 V/V

PDO resolution

24 bit (including sign)

PDO LSB (Extended Range)

0.128 ppm

PDO LSB (Legacy Range)

0.119… ppm

Preliminary specifications:

Measurement mode

Potentiometer (3/5-wire)

Basic accuracy: Measuring deviation at 23°C, with averaging, typ. 2)

without Offset

< ± 0.005 %FSV
< ± 50 ppmFSV
< ± 50 µV/V

with Offset

< ± 0.015 %FSV
< ± 150 ppmFSV
< ± 150 µV/V

Offset/Zero point deviation (at 23°C)


< 140 ppmFSV

Gain/scale/amplification deviation (at 23°C)


< 40 ppm

Non-linearity over the whole measuring range


< 30 ppmFSV



< 2 ppmFSV

Noise (without filtering, at 23°C)

ENoise, PtP

< 105.0 ppmFSV
< 820 digits

ENoise, RMS

< 18.0 ppmFSV
< 137 digits

Max. SNR

> 95.1 dB


< 0.18 Potentiometer measurement 1:

Noise (with 50 Hz FIR filter, at 23°C)

ENoise, PtP

< 9.0 ppmFSV
< 70 digits

ENoise, RMS

< 1.5 ppmFSV
< 12 digits

Max. SNR

> 116.5 dB

Common-mode rejection ratio (without filter) 3)

tbd Potentiometer measurement 2: typ.

50 Hz:
tbd Potentiometer measurement 3: typ.

1 kHz:
tbd Potentiometer measurement 4: typ.

Common-mode rejection ratio (with 50 Hz FIR filter) 3)

tbd Potentiometer measurement 5: typ.

50 Hz:
tbd Potentiometer measurement 6: typ.

1 kHz:
tbd Potentiometer measurement 7: typ.

Temperature coefficient, typ.


< 2 ppm/K


< 2 ppmFSV/K

Largest short-term deviation during a specified electrical interference test

tbd %FSV = tbd ppmFSV typ.

Input impedance

(internal resistance)


2) A regular offset adjustment with connected potentiometer is recommended. The given offset specification of the box module is therefore practically irrelevant. Therefore, specification values with and without offset are given here. In practice, the offset component can be eliminated by the functions Tare and also ZeroOffset of the box module or in the controller by a higher-level tare function. The offset deviation over time can change, therefore Beckhoff recommends a regular offset adjustment or careful observation of the change.

3) Values related to a common mode interference between SGND and internal ground.

Potentiometer measurement range

Potentiometer measurement 8:
Representation potentiometer measurement range

Note: In Extended Range Mode the Underrange/Overrange display in the PDO status has the character of an information/warning when the nominal measuring range is exceeded, i.e. no Error is displayed in the PDO status and LED. If the technical measuring range is also exceeded, Error = TRUE is also displayed. The detection limit for Underrange/Overrange Error can be set in the CoE.

In Legacy Range mode, an Underrange/Overrange event also leads to an Error in the PDO status.