PCI 6503 Voltage Drop

[TreeCropsIPM]

Hello,

I am working on a Windows 10 computer and Labveiw 2018 with a PCI 6503 connected to a CB-50 LP (NI part # 777101-01) terminal block. Hall sensors are wired into the block and powered by pin 49 (+5V) from the PCI 6503. For the past month, I have had 18 sensors wired and powered by the PCI device through the terminal block. However, today I noticed the voltage dropped to zero, and the sensors could not function. I disconnected all the sensors but one, and the voltage returned. As I rewired, the voltage decreased with each device I connected. I can only wire 6 of my 18 sensors before the voltage is too low. I have confirmed the voltage directly off the PCI is 5+V.

Any ideas on what the issue could be? 

Thanks

[santo_13]

It may be a damaged hall sensor consuming high current causing the supply to pulled down, but, before getting to that assumption, try procedurally debug the issue to narrow down the root cause,

1. Connect a DMM in ammeter mode in series with the sensors and check the current consumption of each sensor
2. Ideally, all sensors must be close. See if total sensor current consumption is <1A (limit by the 6503)
3. Document the voltage drop as you add each sensor like sensor1 = 5V, sensor1+2 = 4.95V etc., until all 18 sensors are connected

With the above data, you may be able to identify the root cause.

Please note that there is a self-resetting fuse inside 6503 as per the user manual