Micro830, Analogue

Hi All,

Getting to grips with the Allen Bradley Micro830 2080-IF4 analogue module and have a query on the analogue input side.

I have 2 options; voltage (0-10V) or current (0-20mA)

My understanding;
voltage - if using a pot (high KOhm), I could put 0V and 10V across it and use wiper as a voltage divider for the input into the 2080-IF4 analogue module. I have a common and voltage input, would I tie the common to 0V?

current - using a pot again - common to one side of the pot and the wiper connected to the current input, varying the resistance which will current limit the input into the 2080-IF4 analogue module.

Am I close? and why would you use one over the other?

Thanks

Craig

and why would you use one over the other?

Click to expand...

If you had a sensor that output 0-20 Ma

0-20 Ma circuits are inherently immune to noise

If you had a sensor that output 0-10 v

Am I close?

Click to expand...

without knowing the specifics of your application, I would say you are.

with the voltage thing , it's never going to be above 10v ... I don't know what you have connected to the current thing, but when the pot is turned to no resistance, the PLC is gonna get the full joy

current is more noise immune, and 4-20mA gives you a wire break detection (0mA). voltage is often simpler to troubleshoot. For pots, I have always seen them connected as voltage inputs, one end and the wiper in series with the "+" and the "-" connected to common.

Thank you both realolman & OkiePC, this is making things make more sense. Will give these a go on my test rig over the next few days.

OkiePC, your comment in your signature "It's not all the variables I am most concerned with, it's the undiscovered constants." made me laugh (and also so true!)

OkiePC said:

current is more noise immune, and 4-20mA gives you a wire break detection (0mA). voltage is often simpler to troubleshoot. For pots, I have always seen them connected as voltage inputs, one end and the wiper in series with the "+" and the "-" connected to common.

Click to expand...

realolman said:

If you had a sensor that output 0-20 Ma

0-20 Ma circuits are inherently immune to noise

If you had a sensor that output 0-10 v




without knowing the specifics of your application, I would say you are.

with the voltage thing , it's never going to be above 10v ... I don't know what you have connected to the current thing, but when the pot is turned to no resistance, the PLC is gonna get the full joy

Click to expand...

Ultimately, the PLC will be controlling a directional proportional hydraulic valve driving a hydraulic cylinder. The feedback loop will be achieved by a linear potentiometer attached to the cylinder. Was just trying to get it clear in my head how I was going to connect the pot to the analogue input, however now I realise it will be voltage using the pot as a voltage divider.