Analog input on S7-314

rpop91

Member
R
Join Date
Mar 2012
Location
Detroit, Mi
Posts
44
Hey Everyone,

I'm having some difficulty getting the correct reading on my analog input card. My setup is as follows: S7-314 CPU with built in analog card. Keyence laser sensor that reads distance and reports over analog output.

What I have done so far: I have set both the sensor and my analog input to 4..20mA, there is no physical hardware switch on these cards it is done in the HW config in step 7. I have tested my input with a multimeter and it is reading what it should.

However, when I monitor it PLC side im getting -16, flickering between -16 and -32. I've tried using FC105 and have done everything that was recommended in another thread I found on here with no luck.

Any help you guys can offer would be greatly appreciated.

Thanks again!
 
Are you seeing the -16 directly from the PIW or after the scaling? If you are reading a -16 integer on the PIW prior to scaling and you are reading the proper reading from your source then there is an issue with the wiring. Are you testing the source with a 4-20 simulator or are you reading current directly from it? If you are reading current directly from the device without providing power then it is a 4-wire and the device is being powered elsewhere.
 
Yes I am seeing the -16 directly form the PIW.

Sorry yes I do have a 4 wire set-up. I misunderstood earlier. I was reading current directly from the source.
 
So you have your device directly connected to AI I and AI_ ? Do you have your AI_ connected to Mana?

do you have a 4-20mA simulator? If so try disconnecting the device and connecting the simulator in source mode to the card. If source mode doesn't work try simulate mode. If neither work then there is a wiring issue or a bad card.
 
Whats the catalog number? Either way the simulator should work on either simulate or source to the two points you connect the 4-20 mA into. if the simulator doesn't work on either mode then it is likley wiring or hardware.
 
Do you have the 4-20mA signal connected to terminal 3 for channel 0, and the return signal to the laser on terminal 4 ?

Try with one of the other channels in case channel 0 is defective.
Connect the 4-20 mA signal to terminal 6 for channel 1, and the return signal to the laser on terminal 7.

Or connect the 4-20 mA signal to terminal 9 for channel 2, and the return signal to the laser on terminal 10.
 
Same result on 9,10.

Though Now i am seeing 0 when i should be seeing 4mA. and 27616 when i should be seeing 20mA. So now I'm thinking my scale factor might be off. SHould my hi and lo on FC105 be set to 0 and 100?
 
OK guys I got it working.

Turns out I was using the scale block incorrectly. I was trying to get my output scaled value to match what my input was reading and then I was going to scale it again after. Didn't realize that FC105 scales it for me.

I changed it to UNIPOLAR and set my HI and Lo limits to match the source and I got the output reading that I needed.

Thanks for the help all!
 

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