Analog Out

[kcor 1]

Could someone explain how to set up and program the omron analog output card using a cqm1h plc? Want to control a I/P type valve with a 4-20ma output from a omron. Have a pressure transducer going through a sensotec in line amplifier that gives a 0-5 volt output. Want to start with I/P valve fully open and then as more pressure is detected from sensotec amplifier connected to a pressure transducer then close the valve according to the pressure measured. Have a pretty good understanding of the analog input card, but not so sure of the output card. If someone has done similiar application, could you post it. Thanks

[Chris Elston 79]

I probablly should not reply...but I will explain what I've done with AB stuff. The analog output card on an AB card works with an interger value you place into the output address. It's linear. So the bigger number you move into the output address, the more amps or more voltage the output card spits out. In AB, there is a nice function called the RAMP function, handy for ramping up motors etc...you can place an interger value of "0" in the output address then "RAMP" "0" to "30,000". 30,000 could = 10 VOLTS or in your case 20 mA. And this number is exactly linear or proportional to the amps going out of the card. I would assume that Omron works the same way. I could be wrong, but I figured I try to keep in general enough that you might be able to see how it works.

[Sleepy Wombat 27]

chakorules has put u in the right direction in regards to the operation of the analogue output card in as much as: This would imply that if u had a low pressure (0V input) then u want the valve to be fully open (20mA out) , and as the pressure increases (5Volt) the valve it to shut (4mA). Assuming that you want a linear relationship this implies a gradient or slope (once u plot this on a graph) with a negative slope (ie \ direction), BTW this is how a typical temperature controller working in heat mode (reverse operation). If you are not going to use the PID funciton then might i sugget to take a look at the APR, SCL, SCL(2), SCL(3) functions. In the CQM1H PLC this function along with the PID function are known as expansion funcitons. Therefore u need to map these functions into the PLC using Funciton Mapping Option in Syswin or Double click on the Expansion Funciton Tab in CX-Programmer. Just remember to turn on the Dip switch 4 on the PLC when using these instructions. The analogue output cards (either the CQM1DA022 or CQM1DA041) can output a (-10V) to +10V signal or 0mA to 20mA. The output is determined by how u wire it up. The address of the outpus is determined by the position in rack so to speak. Thats all. So if u wanted a 4mA to 20mA then send to the output a value of (&409 (decimal)for 4mA and &2047 (decimal) for 20mA). Note that u need to send a binary (HEX) decimal number to the output card. BCD won;t work. If your calc's are using BCD then use the BIN function to conver BCD to Binary.