Continious 5V output on PFI0 of BNC-2090

[MLVDR]

Hi all,

We do have two NI systems:

- BNC-2090A with a USB-6251 (Mass)

- and a BNC-2090 with a DAQcard 6024E.

Both systems work perfectly while when triggering them externelly over the PFI0 channel by an externally powered device sending TTL pulses.

Now instead of using this device I build a simple pushbutton powered by the +5V line of the terminal connectors on the boards.

While this works perfectly for the BNC-2090A with USB-6251 it doesn't work for the BNC-2090 with DAQcard. 

If I hook the PFI0 line up to an ossiciloscope I notice a continious 5V output being present. When I connect the externally powered device to

the PFI0 line as well, I can see the output dropping to 0V *(this makes it work as a proper triggering line again with 5V pulses). When I change the externally powered device for my pushbutton,

the output stays 5 V and the pushbutton action just produces a tiny ripple on the 5V output obviously not being identified as a trigger.

(The BNC-2090A gives a 0 V output on the PFI0 line independent of what I hook up to it)

For several reasons I prefer using the BNC-2090 with my DAQCard. 

Any thoughts on how I can trigger over the PFI0 line with my simple pushbutton (and why the output always is 5V...)?

Cheers 

Mark

[Marshall_B]

Hi Mark

Have you recently purchased the BNC-2090A?  There could be a difference in the way you have set up each of the devices.  For instance, have you set all the jumpers in the same way for both connector blocks?

Could you also let me know how the push button is set-up on each device?  How have you wired each of the devices within each individual system of BNC connectors?

You may find the following Knowledge Base article useful:

http://digital.ni.com/public.nsf/allkb/5B5266C6078662648625727A00595EE3?OpenDocument

as it outlines the differences between the two BNC-2090/BNC-2090A devices.

Kind Regards

[MLVDR]

Hi,

The set-up between the systems do exactly match eachother, it's only the board being different.

The PB is powered by the +5V/grnd from the terminal block  The PB signal output is connected to the PFI0 in the BNC-2090A and PFI0/TRIG1 in the BNC-2090.

Although I do get the differences between the systems it doesn't explain the different outcomes to me.

Kind Regards,

Mark

[Brad_K · Accepted solution]

Hi Mark,

The 0 V vs. 5 V difference is explained here: Major Differences Between E Series, M Series, and X Series DAQ Devices

Internal resistors on the PFI lines have changed between the E Series and X/M Series. The E Series devices have a ~50 kOhm PULL UP resistor connected internally to each PFI line, while the X/M series have a ~50kOhm PULL DOWN resistor.

Brad

[MLVDR]

Cheers, that makes sense and explains my problem.

Mark