s7-300 2/4 wires

Moustafa Elsherief · Dec 13, 2015

Hello everybody

I have CPU S7-300-2DP-PN , AI "331-7KF02-OABO" AND ABB DRIVE AC880

I WANT TO WATCH ITS SPEED ON HMI

AFTER CHECK THE DRIVE OP IT 0-20mA

AT AI MODULE IF I CHOOSED 2 WIRES NO OPTION FOR 0-20 ONLY 4-20
IF I CHOOSED 4 WIRES THERE IS 0-20 MA OPTION

AND DRIVE IS TWO WIRES.

if i choosed 4 wire return value of fc105 is 8

PLEASE CHECK ATTACHED

Any one can help??

danw · Dec 13, 2015

On some Siemens Analog Input modules, there is a selector switch (a square black thingie on the outside of the module) used to choose either '2 wire' or '4 wire'.

There are only 2 terminals for either '2 wire' or '4 wire' selection', but the '2 wire' selection puts 24Vdc power onto one of the two terminals. It's called an 'active' input and it is intended to provide 24Vdc power used to provide 'loop power' to a 'loop powered, 2 wire' field transmitter.

The 4 wire selection does not have any voltage on its input terminals. It is assumes that field device provides power to an active 4-20mA output.

I suspect that the AC880 drive is an active output; that the AC800 powers the 4-20mA signal internally because the 3rd screen shot of the drive's analog output makes no mention of passive or requiring a DC power supply.

If the AC800's analog output is indeed an active output, then you would select the Siemens '4 wire' option and rotate the square selector thingie so that the alphabet letter corresponding to the 4 wire selection is the one used. Connect (+) to (+) and (-) to (-) and things should work.

The letters C and D are used for 4-20mA but I can't remember which is 2 wire and which is 4 wire. Your analog input manual will tell you.

Moustafa Elsherief · Dec 14, 2015

danw said:
On some Siemens Analog Input modules, there is a selector switch (a square black thingie on the outside of the module) used to choose either '2 wire' or '4 wire'.

There are only 2 terminals for either '2 wire' or '4 wire' selection', but the '2 wire' selection puts 24Vdc power onto one of the two terminals. It's called an 'active' input and it is intended to provide 24Vdc power used to provide 'loop power' to a 'loop powered, 2 wire' field transmitter.

The 4 wire selection does not have any voltage on its input terminals. It is assumes that field device provides power to an active 4-20mA output.

I suspect that the AC880 drive is an active output; that the AC800 powers the 4-20mA signal internally because the 3rd screen shot of the drive's analog output makes no mention of passive or requiring a DC power supply.

If the AC800's analog output is indeed an active output, then you would select the Siemens '4 wire' option and rotate the square selector thingie so that the alphabet letter corresponding to the 4 wire selection is the one used. Connect (+) to (+) and (-) to (-) and things should work.

The letters C and D are used for 4-20mA but I can't remember which is 2 wire and which is 4 wire. Your analog input manual will tell you.

Thanks for that
regarding to choosing A,B,C or D it is seen after chossing like attached

KalleOlsen · Dec 14, 2015

And you got it working?

Kalle

Moustafa Elsherief · Dec 14, 2015

KalleOlsen said:
And you got it working?

Kalle

Not try yet

Moustafa Elsherief · Jan 6, 2016

KalleOlsen said:
And you got it working?

Kalle

yes it is

s7-300 2/4 wires

Moustafa Elsherief

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