How do you measure resistance and/or amperage?

[ET]

I've got a set of height-control skies for a paving machine which I need to measure.
They are essentially a potentiometer, hooked up to a pivot point.
So, as the arm rotates, the resistance of the circuit changes, which is how you measure the angle.
How do I configure a multi-function input pin on an MC50 to read this, either by directly measuring the resistance, or by measuring the amperage on the input pin, and working out the resistance with math?

[BRIan]

Use any one of C1P27-C1p30 and set PinConfig to 1 then Ohms is available on the bus

[ET]

Thanks!
I assumed that it wasn't available, since I was looking at pins 23-26.

[Jakob]

Have you considered setting it up as a simple voltage divider?
Just by connecting a resistor in chain with your sensor, and then supplying the +5V power.
It may not be optimal, but it is an option.

[Rafal_Typiak]

I have a question regarding resistance measurements. I know that you have to use Rheostat inputs to get a value but what's the reference point? Is it ground or Vcc? I'm asking since whenever you have a resistance sensor you always have two pins. Makes sense when using an Ohm meter. But where's the reference pin in an MC controller? And a follow up question, how does the process of measuring resistance look like, from the MC's side of things? Should one of the sensor pins be connected to the 5V sensor power pin and the other to the measuring pin?

Thanks in advance,
Cheers,
Rafa?

[acmall]

I believe the measurement is referenced to ground and is internally pulled up to the 5v rail. Take a look at the following document that shows the input configurations.

Input Configurations for PLUS+1® Controllers Technical Information Manual
http://files.danfoss.com/documents/input%20configurations%20for%20plus%201%20controllers%20technical%20information%20manual/520l0931.pdf

I am not sure how up to date this is as I had some issues with frequency inputs when set up as described within.


There is also one for outputs.

Output Configurations for PLUS+1® Controllers Technical Information Manual
http://files.danfoss.com/documents/Output%20Configurations%20for%20PLUS%201%20Controllers%20Technical%20Information%20Manual/520L0922.pdf


Alastair

[Rafal_Typiak]

Thanks for this document. It's awesome

oh...  and thanks for helping me out, as well.
 
Cheers,
Rafa? Typiak