Linear potentiometer on Beckhoff PLC

[Jasper_]

Hello,

We are currently working on a project that involves connecting a linear potentiometer to our Beckhoff PLC. After researching, we identified the EL3255 as a suitable EtherCAT Terminal with 5-channel analog input specifically designed for potentiometers (300 Ω…50 kΩ, 16 bit).

Our plan is to supply either 10V or 24V to the potentiometer and then route the wiper connection back to the input. This approach would allow us to effectively monitor the potentiometer's position.

However, we encountered a challenge related to the potentiometer's maximum recommended wiper current, typically specified as 1µA or 1mA (for 1 minute during an error). The EL3255 documentation mentions a maximum output current of "0.3 A total supply current for the potentiometers."

Our question is whether it is possible to adjust the output current through the Beckhoff settings. Alternatively, do you have any recommendations on ensuring that our current remains below the 1µA limit as recommended by most potentiometer specifications?

Thank you in advance for your assistance.

Regards,
Jasper

 

[LadderLogic]

Looking at the data for EL3255, it can be seen that:

- The terminal provides 10 VDC power for each potentiometer

- The internal resistance for each wiper input is at least 100 kOhm. The largest potentiometer resistance it can work with is 50 kOhm Which means the smallest current that can be detected is 10 V / 150 kOhm = 7 µA

1 µA the max potentiometer current? Way too low, I think.

0.3 A is the max total 10 V supply for all the channels you use.

 

[Jasper_]

Looking at the data for EL3255, it can be seen that:

- The terminal provides 10 VDC power for each potentiometer

- The internal resistance for each wiper input is at least 100 kOhm. The largest potentiometer resistance it can work with is 50 kOhm Which means the smallest current that can be detected is 10 V / 150 kOhm = 7 µA

1 µA the max potentiometer current? Way too low, I think.

0.3 A is the max total 10 V supply for all the channels you use.

Well 2µA is the potentiometer max, but I did find a different one with 1mA so that will work. The EL3255 does say ">> 100kOhm", possible they just put 100kOhm and >>, but the actual value been a lot higher so no one complains after breaking their potentiometer?