pci 6221 counter signal reference

[dsdds]

Hello

I have same problems when i use the counter of the board pci 6221.

The problem is,

- when the signal is less than 5/4 vols the counter dont measure. So i would like know how is possible measure signals more low than 4 volts. Because i have another board (pci6023E) and with this board i dont have ths problem. The conuter works very well.

I don t know if is necessary put any kind of reference.  

in Attachment i send the kind of signal i have and is possible measure with the board pci6023E but dont work with the board pci 6221. In this signal i measure the number of fallings.

Thanks

[dsdds]

I will be more specific.

I want replace the board 6023e by a 6221 but i have problems with the counters.

When i try use the board 6221 this board dont count anything (0 counts). I test the board and this board count when i use a TTL signal but effectivetly my signal is not a TTL. But I dont understand why works with the board 6023e  and with  this board (6221) dont works.

 Is necessary put any kind of reference because my signal is more low than 5volts (TTL signal).

Thanks

[ClementG]

Hi,

Have a look at the spec sheet below. Page 7 gives the input level of low and high state.

Regards,