DAQ protection

[hax]

Hello,

I am currently using one of the 6024E series boards and have noticed that nobody has connected up the PFI0 channel to the interface. I was wondering if the circuit I have attached would be appropriate as protection between the interface and DAQ card. The person who initially wired up the other interfaces seems to have used a similar setup.

Thanks,

Harry

[hoffiz]

Hi Hax,

Let me first make sure I understand your issue, you have a 6024E that is connected to an interface. This interface it’s connected to the PFI0 line which in your card is also the AI START TRIG. So you will like to know if the schematic you attached would be an appropriate protection for the pin.

My guess is that you are trying to avoid exceeding the maximum input voltage ratings, which are listed in the I/O Terminal Summary table in the specifications document for the 6024E, page 2.  In this case you are making sure that either you don’t source more than 5 mA at 0.4 V or more sink 3.5 mA at (Vcc – 0.4).

I tried your circuit on Multisim and it seems to do the job fine for a 5V Vcc if you are sourcing to the 6024e. I avoided the 10mF capacitor because for a DC value it will behave like an open circuit. Since I don’t know your interface output specification I will strongly suggest to tested yourself. A little bit more information on this interface will be useful to better assist you.

I hope it helps

Message Edited by Jaime F on 12-14-2007 12:38 PM