Hello Experts ,

Actually , I need to configurate an analog Input 4-20mA , I choose 2 wires , so when I start simulation , I obtain 32768 each time a change input speed , also when I calculate the current of the analog Input  in mode stop, I foudd 57mA , i don't know where this value's current comes from , can you tell me the right configuration that I should do .

To add  I use this tinput analog :31-7KF02-0AB0

Hello,

I recommend for first check signal from transmitter/source with multimeter. Putting sensor to card without first check is hazard in my opinion. SOme cards also have on one side connectors which can set required sensor type due connection and channel. Check this also in S7-300 manual or exact type of module help.

Hello,

I have faced similar type of problem.

I just short the 0V of power supply (which is used in that PLC and AI module) with the Negative terminal of 4-20mA of the source.

Hello hajar08

If you used transducer, first check is it four wire or two wire transducer. then configure the software 2 wire or 4 wire sensor.

because 2 wire transducer, one cable used for operating voltage 24 volt and it's supply from PLC analog module and another cable receive 4-20mA from transducer. This type transducer you have to configure 2 wire sensor

 If you used mA generator and connect with PLC, you see your multimeter showing 57 mA if you don't configure 4 wire sensor.

Thank you

hi,

the difference between 2-Wire and 4-wire-transducers is that the 2-wire-transducers have their power supply through the measurement-wires. Thats the reason why only 4..20mA-range can be used with it.

With a "3-wire-device" you have definitely a seperate power supply, so we can say it is a 4-wire-transducer, but with the "-" of supply and measurement bridged.

Don´t forget the Measurement range module. It has to be on position C for 4 wire-transducer or on position D for 2-wire-transducer. you find it on the side of the module.

hope this helps,

regards,

 

I have another question please , sometimes I get a negativ value , do u have any idea ?

thank you 

Hajar

hajar08

I have another question please , sometimes I get a negativ value , do u have any idea ?

thank you 

Hajar

 Do you use a SCALE function or not?

Hajar

have another question please , sometimes I get a negativ value , do u have any idea ?

thank you

Hajar

 Hello,

pls describe your now used sensor type, range of meassure, set range in module and what exactly negative value +/- you see. Simply your infos are not suficient for better help...

hajar08

I have another question please , sometimes I get a negativ value , do u have any idea ?

thank you 

Hajar

hi,

If you have a negative value, there are maybe less than 4 mA.

Have a look in the manual,chapter 5.1 "Representation of the values for analog input channels"

SIMATIC S7-300 S7-300 Module data

see the table on page 265:

hope this helps,

regards,