Dear Micaela ,
Thanks fopr your reply.
i found that when i put resistor between the input line and ground (pin 50) the signal is stable.
so, i connect for each line resistor and everything is perfect now.
i do not connect the relay 24V directly to the pci 6509.
i also talk with my local NI office and they told me that what i do (connecting the resistors) was verry good.
they also told me to look in MAX in pci6509 properties and to uncheck the Tristate which is the default for the port i configure (port2)
i didnt uncheck it, but the resistors solve the problem.
Thanks for your help.
if you can direct me to link about Tristate, what and when i need to use it, i'll appriciate that.