USB-DIO96H unexpected voltage Drop

[Rwilcox]

Hello, 

I have a USB-DIO96H that I have configured using the UL tools for python.  The unit is configured for 72 Digital outputs and 24 Digital Inputs(though I've attempted only 8 outputs with no change).  Control of the Digital outputs appears to be working as I measure ~5V on high and 0V on low.  I've noticed that when I attach a minimal load to the digital outputs that the voltage is dropping to 3.5V (measured using Multi-meter), which is an issue for my application.  The 5V pin seems to be unaffected.  I've even gone to the point of attaching a 10K resistor from a digital output to GND (Nothing else is driven high) and still I measure 3.5V(should be a .5mA draw).  I have a second USB-DIO96 and it's behavior is identical.   To config the port, I call (Just the library calls for reference):

ul.get_daq_device_inventory(InterfaceType.ANY)

 ul.create_daq_device(board_num, device)

ul.d_config_port(self.board_num, DigitalPortType.FIRSTPORTA, DigitalIODirection.OUT)

 

Am I missing something in the config?  Should the USB-DIO96 be able to source .5mA without dropping to 3.5V? The specs state that I should be able to source 24mA per port.  (My USB-1408FS is able to source .5mA with no voltage drop)

Thank you in Advance,

Robert

 

[JRys]

Hello,

We do not guarantee 5 volts only 2 volts or more. Check the specs in the back of the user manual. 

The USB-1408FS uses a different output chip that is able to maintain a higher voltage when supplying current. The specs indicate 3.8 volts a 6mA.

As for your  10k ohm test load, it could be that it's forming a voltage divider with the 47k pull up resistor.

Best regards,

John