PLUS+1 Hardware > Controllers

How to make the MC050 produce a 4-20mA signal?

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oiltronic:
How do I connect the MC050 to a valve that requires a 4-20mA input signal?  Is there a standard accepted way to do this?

I've tried connecting a PWM output to a Phoenix signal conditioner, 2-10V in and 4-20mA out, but the signal conditioner doesn't seem to like the MC050's PWM signal.  Is there a signal conditioner that is known to work (converting PWM voltage to 4-20mA), especially so I don't need any intermediate parts?

Failing that, what about a simple RC filter on the PWM output, which still drives a signal conditioner?  Anyone know of a combo that works?

Quax76:
The MF outputs of the MC050-10 allows you to use it as a current output.
PinConfig: 4 --> 0 - 30000 [0.1 mA]
Your value must be scaled from 40...200 and then connected to "OutputValue"

oiltronic:

--- Quote from: Quax76 on January 16, 2013, 08:17:22 AM ---The MF outputs of the MC050-10 allows you to use it as a current output.
PinConfig: 4 --> 0 - 30000 [0.1 mA]
Your value must be scaled from 40...200 and then connected to "OutputValue"

--- End quote ---

Thanks for the suggestion, but does this actually work for you? Closed-loop PWM mode is used for driving current, and typical 4-20mA inputs have at least a few hundred ohms impedance, so that shouldn't work:


--- Quote from: Page 18 of the Plus+1 Controller Family Technical Information, 520L0719 Rev KA Nov 2011 ---In closed loop mode, current is sourced and a constant current is maintained by the module’s operating system using internal current feedback. Load impedance must not exceed 65 ohms.

--- End quote ---

And page 19 states the minimum current as 10mA, repeatability and absolutely accuracy as 0.5% full scale (0.5/100*3000mA=15mA). So it's very misleading for the software to allow a 0.1mA resolution, when the accuracy is no better than 15mA.

I also recall reading somewhere that this is not recommended for low current values because of the inaccuracy at that range, but I cannot find where that is written. I believe that the current output is intended for driving coils that need power on the order of a hundreds of mA.

Neil:
Hi

See attached

Neil

jsaluk:
Axiomatic makes a signal conditioner from PWM to 4-20
Contact at sales@axiomatic.com.
Product group is PWMI-***
Hope that helps

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