Analog problem

BoSChoW

Member
Join Date
Apr 2006
Location
Nova Gorica
Posts
107
Hi all,
I use CPU313C which i program in Siemens SIMATIC Step7 and OP7. I have connected the measure probe "tool" to the analog input 1, i made a variable table to see the changes of analog values but insted of a scale i recieve just 10 and 0. In the HW confing i have configured that AI1 is a voltage type and the voltage scale from 0..10V. I dont know if i did something wrong, or i have forgot to do something. If anyone knows how to solve my problem pls respond. Thanks for yout time and help.

Regards BoSCHoW.
 
Place the PIW of AI1 in the variable table. It should give you a value between 0 (=0V) and 27648 (=10V) If it doens't, than either your connection is not correct or the hardware configuration is nog correct.

For connections check Siemens manual: Programmable logic controllers S7-300 Module Data, chapter 4. (A5E00105505-03)

For hardware config, make sure that the output of the sensor is equal to the input of the analog input.
e.g.
+/- 10V = signal from -10V to +10V
4..20mA = signal from 4mA to 20mA

 
Hi, now the analog input is showing the value fron 27648 to 0. The remaining this that i have to do is scale. I dont know how to start, does anyone have some tips about this. Thx and regards.
 
Hi again and a new problem emerged, i tryed to use FC105, and it worked fine when i inserted the value for analog output in the variable table "27648". Now my question is how do i modify the value in the FC105 or do that the scaling will work always ?
Thx and regards.
 
I usualy do a scale like this...
First move the PIW value to a datablock(let's say db10.dbw0 <-- integer)and then use the converter functions...
from integer(db10.dbw0) to double integer(db10.dbd2), from double integer(db10.dbd2) to real(db10.dbd6). When you have the real value you can set your scale...
For instance if you have a tepmerature probe wich has a range from 0-50°C. When the probe will register 50°C the value at PIW will be 27648. So you devide 50 with 27648. You get 0.001808.
Now you just multiply this value with the real value reading(db10.db6) and you'll get the exact reading of the temeperature.

I can post a screen shot of the code if you want.
Hope it helps
Regards
Ales

PS: You can allso use the memory block of course(MD, MW's)...
 
Hi Ales, this would be a great idea so please post a screen shot of the code. I have just figured out something, that i have to put the 27648 value in the analog output and then the input will read the position of the measuring potenciometer (or something like that), but with your help i can finish this scaling sooner. I have decided to do my own scaling. Like you suggested i started to convert the integer to double intiger and finnaly to real. Thanks a lot ang regards
Bostjan
 
Last edited:
BoSChoW said:
Hi Ales, this would be a great idea so please post a screen shot of the code. I have just figured out something, that i have to put the 27648 value in the analog output and then the input will read the position of the measuring potenciometer (or something like that), but with your help i can finish this scaling sooner. I have decided to do my own scaling. Like you suggested i started to convert the integer to double intiger and finnaly to real. Thanks a lot ang regards
Bostjan

This is the srceen shot of the code. The only difference from what I explained before is that the last value is multiplyed with 0.00360, so that the scale is from 0 to 100!



Regards...
Ales
 
For FC105 and you want to scale 0.0 to 100.0, just put the analog input on the input handle (ie: PIW288) and 100.0 on the hi-limit and 0.0 on the lo-limit. if you are trying to go +- put a positive signal on bipolar. the output will be a real value 0.0 to 100.0. A word of warning, if the input goes out of range, (<0 ro > 27648> the output will freeze at the last good value and the ret-val will give you an error.
 
Now everithing works fine exept that i can't reach the value 0 ? The analog input is showing values between 27648 and 27360. Anyone knows why is working like this ?

Regards Bostjan.
 
It sounds like the configuration is wrong. You may be using 4-20ma and have the default configuration of 0-10. Check your hardware config.
 

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