analog inputs ??

hey folks ...

i have a question regarding analog inputs in s7 200 plc's
what does A+ / A- / AR means ...and how can i connect them to the sensor i mean what kind of sensor ... i herd that there 2 wire type and three wire type ?? is that correct... and please give enough details about HOW TO CONNECT the sensor to the A+,A-,AR, inputs.

thanks in advance...
kumar.

[jvdcande]

Kumar,

the meaning of those connections is:

• A+: analog input - positive side
• A-: analog input - negative side
• AR: analog input - resistor

The how to connect part is to be found in the "S7-200 Programmable Controller - System Manual" in chapters A.28 "Expansion Module EM231 Analog Input AI 3 x 12 Bits" and A.29 "Expansion Module EM235 Analog Combination AI 3 / AQ 1 x 12 Bits".

Kind regards,

hi jvdcande,
thank you for the reply ...

i have the manual that came along with the micro win document cd
but the part which i dont understands ...which of these A+ A- AR
give the PLC analog input the 0 to 10v signal,do you mean that the
A+ , A- are the power supply from the plc to the sensor ,and the AR is the sigle returned from the sensor to the plc input ?

can you please explain more jean ..... thank you in advance.

bebst regards .kumar.

[jvdcande]

do you mean that the A+ , A- are the power supply from the plc to the sensor ,and the AR is the sigle returned from the sensor to the plc input ?

NO! The voltage output of the sensor has to be connected to both the A+ and the A- input as can be seen on the first figure in chapter A.28 (in my case figure A-27).

If you are using a current sensor, you have to connect the positive side of the sensor to both the resistor and the positive input of the module (shown are RC and C+) while the negative side of the sensor is to be connected to the negative input (here C-). In this way you generate a voltage across the resistor (current-to-voltage converter).

If you don't use a certain input you have to short the positive and the negative inputs (here B+ and B-) to avoid noise readings.

The internals of the module are shown in the fourth figure of that chapter (in my case figure A-30), which should clarify everything. The power supply of the sensors is not shown on these figures and has little or nothing to do with the PLC itself.

Kind regards,