ML1400 Analog Conversion

[bearsgone 1]

Hello I have ML1400 with 1762-IF4 expansion card. How do I go about taking an analog input 4-20ma on expansion card and converting that to 0 - 10 V analog output on the PLC itself. PLC only has two AIs and they can not do 4-20ma only voltage. I presume there is some kind of conversion possible 4-20ma to 0 -10V? Thank you for your help

[Mickey 71]

Which base unit do you have? The analog unit has 2 analog outputs that are 0-10 volt ( 0-4095 raw data) outputs. Or the 1762-OF4 can be configured for voltage 0-10 volts output.

[waterboy 7]

a precision (1%) 250 Ohm resistor accross the input terminals will give you 2-10 V for 4-20ma. You can then scale that range in the ML1400.

[newpageboba 7]

V=IR 10Volts = 20ma times 500 ohms so a 500 ohm resistor will give you 2 - 10 volts Edited 22 Dec 2010 by newpageboba

[bearsgone 1]

I was trying to take scaled value from 4-20ma analog card input, divide that by 163.83 which I think is 1% of 0-16383 range and multiple that by .1 which is 1% of 0-10V range. Assign that value to AI output 0 on the plc itself. Example attached but it does not assign anything to output Please see rung 5,6 and 7 Thanks AI Output.pdf

[Mickey 71]

The base unit's analog output is 0-10volts with 12 bits resolution ( 0-4095 raw data). So just take your analog input scaled for 0-16383 ( 4 to 20ma) and rescale it for the analog output. See pictures below

[bearsgone 1]

Mickey, I get an Error: Operand sizes do not match

[Mickey 71]

Post your .RSS file and someone may spot something. Also tell us the complete catalog number of your processor. Edited 22 Dec 2010 by Mickey

[waterboy 7]

Doh!~

[bearsgone 1]

Looks like MicroLogix can not handle on the fly AI 4-20ma to AO 0-10v SCP scaling. It did work AI into Float, SCP AI float range AO range Analog output Thank you for your help

[Mickey 71]

Post the code that you think is not working. Just curious. And the code that is working. Edited 24 Dec 2010 by Mickey

[bearsgone 1]

Mickey, I have attached working version PDF and non working version. the only difference is that I used float instead of straight Input. Unless I am missing something? working.pdf

[Mickey 71]

Eliminate the decimal point in the input min, input max and the scaled min and scaled max. See my post (#6) above. Edited 24 Dec 2010 by Mickey