NI 9215 and PNP Proximity Sensor

[StuartLamb]

Hi folks

I am attempting to read a photo-electric sensor (Telemecanique XUB9BPBNM12) voltage output using an NI-9215 and cDAQ-9174. The wiring setup is shown below (all credit to Lynn/johnsold from a previous thread on this topic): 

The power supply is a 24V DC mains adaptor so I am using a voltage divider to step the high signal down to 8V. This also acts as a pull-down resistor. 

While the sensor output is low the signal is as expected, with little noise. However when the output is high the signal is dropping to 0V at 50Hz, as shown here:

Suspecting a grounding issue, I set about trying a few things to rectify this.

• Connecting AI- to COM
• Connecting AI- to COM through a 1M resistor
• Isolating the sensor from any conductive metalwork
• Replacing the sensor cable with a shielded one
• Generally moving the sensor cable around looking for any change on the trace. 

None of which had any real impact on the reading. I have also confirmed that both the DAQ module and the power supply operate normally with other sensors (a load cell and pressure transducer, I don't have any alternative proximity sensors available to test). 

Any advice is much appreciated! 

[StuartLamb]

Hi folks

I am attempting to read a photo-electric sensor (Telemecanique XUB9BPBNM12) voltage output using an NI-9215 and cDAQ-9174. The wiring setup is shown below (all credit to Lynn/johnsold from a previous thread on this topic): 

The power supply is a 24V DC mains adaptor so I am using a voltage divider to step the high signal down to 8V. This also acts as a pull-down resistor. 

While the sensor output is low the signal is as expected, with little noise. However when the output is high the signal is dropping to 0V at 50Hz, as shown here:

Suspecting a grounding issue, I set about trying a few things to rectify this.

• Connecting AI- to COM
• Connecting AI- to COM through a 1M resistor
• Isolating the sensor from any conductive metalwork
• Replacing the sensor cable with a shielded one
• Generally moving the sensor cable around looking for any change on the trace. 

None of which had any real impact on the reading. I have also confirmed that both the DAQ module and the power supply operate normally with other sensors (a load cell and pressure transducer, I don't have any alternative proximity sensors available to test). 

Any advice is much appreciated! 

[NIRebecca]

duplicate

[NIRebecca · Accepted solution]

Hi Stuart, 

Can we using Differential measurements? If you photoelectric sensor is using a 24V DC mains adaptor for power we should be connecting the signal reference to the COM terminal too: 

Only if using Single-Ended Voltages should AI- be connected to COM. See Field Wiring and Noise Considerations for Analog Signals for more info. 

Hope this helps, 

Rebecca