Inductive sensor

When you were asked to measure the digital input voltages as you activate the sensors, where is this data?

We are not able to guess the answers without information. 

Stating everything is grounded makes me suspicious because that is not something I would ever say when asked if power supplies were properly bonded.

What is the voltage between the 0V of each power supply?

What is the voltage between the 24V of each power supply?

What is the voltage between the 0V into the PLC and the digital inputs from the IFM inductive sensors when they are OFF and when they are ON?  A table of data would be nice.

I took another look at the sketch of the wiring you posted.

1M for the digital inputs needs to be connected to the same power supply 0V as the IFM sensors use.

It should not be connected to the PLC supply's 0V.

What you are forcing to happen is the return for the sensor power is through the plc, through it's M terminal, to the PLC supply's 0V, and then to the bonding between the supply's 0V and ground, and finally, from ground to the sensor supply's ground bonded to 0V.

If there are any bad grounds, or bad bonding, you will certainly have problems.

There is a maximum amount of common mode current the plc will allow, which it seems happens when more than 5 sensors are active.

marko23

Hati

marko23

Everything is grounded.

 So you are saying that the two power supply's have 0v connected together? That needs to be done, to have the same potential in both power supply's .

 Works fine with 5 activated sensors, there is no reason for not working with 7 activated sensors.

Ahh, you are not correct.  This is my last reply on this topic until you fix your wiring.

marko23

Repeat, works fine with 5 sensor, there is no reason for not working with 7 activated sensors.