Mesa 7i96 Inputs coupled together?

I'm setting up my limit switches (NPN proximity sensors) and am seeing some unexpected behavior at the inputs on my Mesa 7i96. I have the Input Common pulled to +24V, Brown wires to +24V, Blue wires to GND, and Black to the input terminals. Whenever a sensor is triggered it pulls all the voltages lower triggering all the inputs I have connected. I already tried adding a series resistor and a pull up resistor without any meaningful changes. Any suggestions? I'm probably missing something simple. Also, I need to provide a 5V signal to an SSR driving an AC load. Using the isolated outputs isn't turning out to be straight forward since the voltage drop across the transistor brings the output to ~500mV if I hook up 5V to +out and the signal to -out. I'm sure these are solved problems but haven't been able to find the right information. Any suggestions?

On the inputs it sounds like the input common is not connected.
If the input common (TB3, pin 12) is at a fixed 24V, there should be
no interference from input to input at all.

On the outputs, an "on" 7I96 output is less than 0.1 Ohm so a connection
like +5V -->OUTN+ -->OUTN- --> SSRIN+ --> SSRIN- -->5VGND
should put 5V across SSRIN+ to SSRIN-  (when on) within a fraction
of a mV of the 5V source voltage

BigJohnT wrote:

The inputs are sinking so they are looking for 24vdc and the common should be 0vdc, not sure if you can run NPN inputs or not.

JT
 

The 7I96 inputs can be sinking (for PNP sensors) or sourcing (for NPN sensors) depending on how you connect the input common pin

For sourcing inputs (NPN sensors or switches with common of 0V) you connect the input common to +5 to +24V
For sinking inputs ( and  PNP sensors or switches with a common of +5 to +24V) you connect the input common to 0V

Wow thanks for the quick reply guys. Turns out I had an off by one error between my ears. The headers were plugged in to the wrong spot. It's all working now!