Configuring 4-20mA Analog Output signal

Hello,

I need to send a 4-20mA signal to an Analog Output. I have used a PID controller output and converted the 0-100% signal into 4- 20 mA signal using a Scale block. However, this scale block's output data type is Real. I tried separating the the Real (%MD) into 2 %MW and tried writing that to the Output address. However, it did not work when I used %PQW address as the move instructiion was not executing. When I changed the Output address to %QW the move instruction executed but the AO module was still not receiving the signal (4-20). Now, after a bit of browsing I have decided to convert the Real to Uint data type and send that to the AO module. Please see the attached snippet  and advise me if it is correct or not and how to make it work.

The circled part above did not work. I want to know if the circled part below is the right way to do it.

Much appreciated. Thanks.

RZ

 Did you use NORM X and SCALE X for scaling your output from the blocks to output address? For the output to function normally, it needs to receive value like 0- 274658. I am not sure about the number. You can check the manual to find it out and you need to make a scale so that 0-100% is scaled to that value. Only then your output works. I am not having access to my laptop, otherwise I could have shared and example. Also you can search for scaling in this forum.

Thanks,

Jay

rzuhair

Hello,

I need to send a 4-20mA signal to an Analog Output. I have used a PID controller output and converted the 0-100% signal into 4- 20 mA signal using a Scale block. However, this scale block's output data type is Real. I tried separating the the Real (%MD) into 2 %MW and tried writing that to the Output address. However, it did not work when I used %PQW address as the move instructiion was not executing. When I changed the Output address to %QW the move instruction executed but the AO module was still not receiving the signal (4-20). Now, after a bit of browsing I have decided to convert the Real to Uint data type and send that to the AO module. Please see the attached snippet  and advise me if it is correct or not and how to make it work.

The circled part above did not work. I want to know if the circled part below is the right way to do it.

Much appreciated. Thanks.

RZ

 Yes, Jay. I am scaling the 0-100% of the Controller Output to 4-20 mA. I just need to know in what format do I need to send this signal. Since it is a 16-bit Int for the AO module, I went this way of converting Real to UInt. Please see the screenshot.

Jay.

 Did you use NORM X and SCALE X for scaling your output from the blocks to output address? For the output to function normally, it needs to receive value like 0- 274658. I am not sure about the number. You can check the manual to find it out and you need to make a scale so that 0-100% is scaled to that value. Only then your output works. I am not having access to my laptop, otherwise I could have shared and example. Also you can search for scaling in this forum.

Thanks,

Jay

rzuhair

Hello,

I need to send a 4-20mA signal to an Analog Output. I have used a PID controller output and converted the 0-100% signal into 4- 20 mA signal using a Scale block. However, this scale block's output data type is Real. I tried separating the the Real (%MD) into 2 %MW and tried writing that to the Output address. However, it did not work when I used %PQW address as the move instructiion was not executing. When I changed the Output address to %QW the move instruction executed but the AO module was still not receiving the signal (4-20). Now, after a bit of browsing I have decided to convert the Real to Uint data type and send that to the AO module. Please see the attached snippet  and advise me if it is correct or not and how to make it work.

The circled part above did not work. I want to know if the circled part below is the right way to do it.

Much appreciated. Thanks.

RZ

 

 Can you open the FB for Engineering scale to see the conversion?

Thanks,

Jay

rzuhair

 Yes, Jay. I am scaling the 0-100% of the Controller Output to 4-20 mA. I just need to know in what format do I need to send this signal. Since it is a 16-bit Int for the AO module, I went this way of converting Real to UInt. Please see the screenshot.

Jay.

 Did you use NORM X and SCALE X for scaling your output from the blocks to output address? For the output to function normally, it needs to receive value like 0- 274658. I am not sure about the number. You can check the manual to find it out and you need to make a scale so that 0-100% is scaled to that value. Only then your output works. I am not having access to my laptop, otherwise I could have shared and example. Also you can search for scaling in this forum.

Thanks,

Jay

rzuhair

Hello,

I need to send a 4-20mA signal to an Analog Output. I have used a PID controller output and converted the 0-100% signal into 4- 20 mA signal using a Scale block. However, this scale block's output data type is Real. I tried separating the the Real (%MD) into 2 %MW and tried writing that to the Output address. However, it did not work when I used %PQW address as the move instructiion was not executing. When I changed the Output address to %QW the move instruction executed but the AO module was still not receiving the signal (4-20). Now, after a bit of browsing I have decided to convert the Real to Uint data type and send that to the AO module. Please see the attached snippet  and advise me if it is correct or not and how to make it work.

The circled part above did not work. I want to know if the circled part below is the right way to do it.

Much appreciated. Thanks.

RZ

 

 

 It should work. You can use a clamp meter to measure the output current and you can aslo change the percentage and see the change in current. So that you get a clear idea about the output from the PLC.

Thanks,

Jay

rzuhair

So, I did this. Converted the 0-100% signal from PID Loop to a signal of 5529.6-27648.0 [4-20mA]. When I move it to %QW it changes to 16#159A. Please let me know if it will work.