Analog inputs remain at zero, digital works!

Hi all,

I have a few 0BA7 logos running, and have a new 0BA8 now for a next project (24RCE, 6ED1 052-1HB00-0BA8). To test it I modified and downloaded one of my 0BA7 programs ('hardware' changed to 0BA8). This program uses all four analog inputs, so I enabled all four analog inputs through Hardware I/O settings ('set  AI3 and AI4 position, enable 4 AIs'). For testing I connected these inputs to analog DC voltages (somewhere between 2 and 5 V) and expected my program in the 0BA8 to react on that. To my surprise nothing happened!

Then I made a small program for testing the analog inputs directly: all four inputs AI1-AI4 go through amplifiers to analog markers.  The amplifiers are set to signal 0-10V, gain 1x or 10x. A message block on the display shows the amplifier values. Again: no signal!

Then I used  the signal function on the Logo itself (date display, then left arrow until the 'AI' values are visible): All at zero! Next I used the online monitor: again, all at zero!

Then I connected a 10V digital signal to each of the inputs and checked the signaling function again on the Logo display, but now for the digital inputs 'I': when I make the input high, this is visible in the display. To be sure I modified my program to drive an output relay with a digital input signal (I1, I2, I7 or I8): all inputs work!

It seems that for some reason the 0BA8 does not react on analog signals, but it does on digital input.

I wonder if I miss something, but I am running out of options. Does anyone have a suggestion?

Regards,

Gerard

Since you take external voltages for testing, you must connect the 0V terminals of these power sources to the 0V terminal of the supply voltage of the logo.

Whether the analog inputs operate, it can be stated quite simply. Insert + of 24V supply voltage on I7 and see in the logo menu the analog input AI1.It will 1000 units be displayed.

Hi ixo65,

Thanks for the hint. Your suggestion on the ground made me think. I found out that my power connections are marked P1 and P2, not L1 and M! I already wondered  about this when I connected it. Damn! I have ordered the wrong version! I have several 12/24RCE versions 0BA7, but now I have ordered a 24RCE (24V AC/DC). The AC/DC versions do not have analog inputs, only digital! 

Anybody out there that wants to swap this new 24RCE 0BA8 for a 12/24RCE 0BA7 with relay outputs?

Regards,

Gerard

Ps. 0BA7 as a replacement is no typo: I also want to use one older RTD module that is not compatible with the new 0BA8.

I'm having the same problem.  I'm running +24VDC through an 8.2k resistor, with a 470 ohm resistor to 0V from I8.  The I8 on the input screen comes on like it's a digital input, but the input (AI2/I8) is not responding to the change at all. It's like the threshold trigger block is not working. 

I measure 1.2 VDC with 8.2k and when shorted (<50 ohms) I measure 23.5VDC at I8, but my Ax value never changes.  I've tried I7 & I8. 

I have used the same threshold trigger block in several programs on the 0BA6 and 0BA7 with no problem.

I find the threshold trigger setup screen very confusing and difficult to use.  I have a normal input of 1.2V, and want it to turn the threshold trigger output to turn on when the voltage is greater than that. 

It has to act like a normally closed digital input so that if the device is shorted, is damaged or removed, the input turns off.  I'd rather not use any additional components..

yes, I failed to look at the part # assuming I had been given the correct one....problem solved, thanks again!

Hi Guys! i would like to add a comment on this because i had a simillar issue .

I was trying to set up the analog 0-10v on my 0BA4 logo siemens , whic it has two analogs 0-10V on I7 and I8, but i couldn't make it work. The issue was because i was trying to use the AI7 and AI8 as an inputs on ladder ! Instead, i used the AI1 and AI2 as analog inputs and it worked quite well!

hope this helps, Cheers  !