S7-315 Comms & Analog In

[GlennP 0]

Hi all, I have a couple of issues here, I am seting up a 315F-2PN/DP which has a remote rack with a ET200M IM153-1 DP Slave. I have good ethernet comms to my laptop and have good profibus to the remote rack. All modules are available and OK. As seen from the HW config and module Information. I can set my digital outputs in the remote rack so comms isn't an issue. On the processor there is solid red light on BF2 and I can't see where this error is coming from. The other issue I have is hardware related, I think, I can't get a reading from the Analog In. It is a SM331 2xAI. I need 4-20mA so I have moved the square block to "D" and set up 4-20mA 2 wire in the HW config>object properties>Parameter Assignment. I can get full scale movement when I put on my signal generator but thats it. The signal generator is working. The wiring is correct. There are two small key type selectors down by the terminals they seem to be a setup for something but I can't find what for. Do these need to be setup? Any help would be great Glenn

[JesperMP 2]

Hi Glenn. BF2 is for X2 (the ethernet port). Normally it goes off when you attach something to the ethernet port that communicates with the CPU, a HMI or STEP7. If it stays on, then maybe you have configured some connection or i/o group on Profinet ? Anyway, you can get more information on why BF2 is on by investigating the PLC .. Hardware Diagnostics. Is your analog module the 7KB02 ? It is the only 2-channel module I can find. You say that your signal generator works, but not what the problem is. Is it that your sensor doesnt give any signal ? If so, connect a meter in series and see if you have a current in the loop. If not check that the sensor is OK. If the sensor is OK, there is something wrong with the connection of the sensor, or the 24V+ or 0V. The manual isnt very clear on how to connect a 2 wire sensor. One terminal shall provide 24V out to the sensor. You can find that one with a meter. Another terminal shall receive the 4-20mA signal from the sensor. You can find that one by putting your test generator on the terminals. There is something about internal and external compensation. Maybe the key selector has to do with that.

[GlennP 0]

Hi Jesper, Just managed to get back to this project today. I had a look at the ethernet port etc all was good, except the BF2 light was still on. I decided to change the temporary ethernet switch with a smaller one (physically) as my bench was getting full. Guess what? The BF2 light went out.. So I put the original switch in BF2 is back on. Decided to file the original switch in the bin Looking at the Analog Input. I changed the Analog input to 4-wire. It seems that the 2-wire 4-20mA is sinking and the 4-wire is sourcing. Now my 4-20mA generator works on it. Great now I can get on with the rest of my project.