Resistance Measurement Using Siemens Cpu 313c

Dear all friends

i have a siemens plc CPU 313C with integrated analog inputs
one of them can be directly given to a resistance ( as per mannual )

any one can help me in this

i am trying to connect a resistance to the PLC and comparing this resistance with a set value!
example programs will help me to understand more !!

please help me

Resistance measurement 313C

Hello:

First you should configure in HWConfig AI4 as "Resistance 2 wires".

In the program you can read the value in PEW761, I'm not sure if it's 600Ohm = 600 or to 6000.


I hope this helps,
Kelkoon

Thank you sir
i have done that
and how to read that in PEW761??
its showing 600 ohms
please give one example

Hello vikas.vss;

Recently we sent you information on the use, setup and programming of analog data in Siemens S7-300 PLC (with load cells if I remember correctly). What is so different in your current application?

Once you have configured your analog input point to read a resistance value, and selected the correct range, the memory register associated with the channel (look in the Hardware Config editor) will hold the present value (numeric) of the analog signal. Just access it in your program, for a SCALE function, or a Compare or a MOVE if you want to. Or program the address in a VAT table...

For a more comple uinderstanding of analog value representation and programming, I suggest you download the following manual from Siemens' website, and study the chapter on analog modules.
Programmable Logic Controllers S7-300 Module Data

Hope this helps,
Daniel Chartier

dchartier said:

Hello vikas.vss;

Recently we sent you information on the use, setup and programming of analog data in Siemens S7-300 PLC (with load cells if I remember correctly). What is so different in your current application?

Once you have configured your analog input point to read a resistance value, and selected the correct range, the memory register associated with the channel (look in the Hardware Config editor) will hold the present value (numeric) of the analog signal. Just access it in your program, for a SCALE function, or a Compare or a MOVE if you want to. Or program the address in a VAT table...

For a more comple uinderstanding of analog value representation and programming, I suggest you download the following manual from Siemens' website, and study the chapter on analog modules.
Programmable Logic Controllers S7-300 Module Data

Hope this helps,
Daniel Chartier

Click to expand...

dear sir

but that is not working with the resistor with 2 wires
the FC 105 is downloaded in the PLC but as soon i run that the PLC -SF RED led is glowing ( CPU Error)
what may be the reason??
i dont know
please help me

Hello vikass.vss;

but that is not working with the resistor with 2 wires

Click to expand...

You have to realize that an analog module does not care about the type of sensor you connect to its' input channel, as long as it is configured correctly to "understand' the signal it recieves.

the FC 105 is downloaded in the PLC but as soon i run that the PLC -SF RED led is glowing

Click to expand...

Would you mind explaining what the FC105 does? Is this your code to read the analog input? Maybe you could post it here so we may look at the program.

When a S7 CPU goes to SF, the Diagnostic Buffer of the CPU will tell you why it went out of normal run state. One way to access it is to go Online with the CPU from the HardwareConfig editor, while it is still in SF; the your hardware will be shown with explicit symbols for each "defective" module. Double-click on the modules marked with a red X to read information on the defect that the CPU detected. Open the CPU and any module marked in red X to get a complete overview. You can save the error information directly in those screens (as a text file), and publish them here if you need help decipherng the messages.

Hope this helsp,
Daniel Chartier

Dear sir

i use FC105 for scaling the analog inputs ( here now i have two wire resistors)??
is this a right method??
please help me sir

can you tell me some simple method for getting the resistance input and comparing the value of resistance with a set value

if u have some example codes it will be greatfull