[?]: Using Analog Input 2 wire 0-20mA...?

hand_drake · Post by **hand_drake** » Tue Nov 18, 2008 7:15 am

Hello everybody...

How we can use analog input 2 wire but the transmitter is 2 wire...?

Hence, the analog 2 wire of Siemens Step7 (All analog input module) is 4-20 mA, without changing the transmiter, because the transmitter is 0-20mA.

Thanks for answer.

dsekulic · Post by **dsekulic** » Tue Nov 18, 2008 11:16 am

Are You sure that transmitter is 2 wire because transmitter power supply is provide over this 2 wires. That's why 2 wire transmitters have no possibilities to choose 0..20mA range.

regards

hand_drake · Post by **hand_drake** » Fri Nov 21, 2008 1:14 am

Yes, i am sure about this input analog. The input that i obtain is from a feedback control valve 0..100% = 0..20 mA. It's quite strange, but it's true.

charles_ch_tan · Post by **charles_ch_tan** » Fri Nov 21, 2008 4:57 am

2 Wires transmitter, 1 wire for 24VDC whereby another 1 is for Signal (I+).

If your feedback control valve 0..100% = 0..20 mA.
Then in Simatic Manager Hardware Configuration, you might set the Alalog Input from 4-20mA to 0-20mA. Remembered the Jumper Setting at that Analog Input Module Cards it self must set correctly.

dsekulic · Post by **dsekulic** » Fri Nov 21, 2008 8:48 am

Hi,

Do You have link or model of control valve You mentioned?

regards

hand_drake · Post by **hand_drake** » Tue Dec 02, 2008 3:40 am

Ok....
Finally, i make nothing different with the program, but i recalibrated the valve. Using 2 wire analog input there is no 0-20mA, only 4-20mA.

Calibration the valve:
4mA=0% opening feedback
20mA=100% opening feedback

And it works.