What signal is used in the rpm wire for case fans?

[smokafatty]

I have these fan/temp controllers and they require all fans to have a rpm wire connected or else it just does random false alarms. Well, most of my fans don't have the rpm wire so its constantly beeping away. I'm about to pull my hair out or buy new fan controllers.

I was wondering if I could fake the rpm lead, I'm guessing its just a low level voltage signal or something like that. Anybody know?

[richskie]

I would guess its the frequency rather than the voltage thats important. Can't you disable the alarm for your controller?

[smokafatty]

Ya you are right I didn't think of it that way. As the freq changes the volts would stay the same so just supplying a dc voltage wouldn't work as there wouldn't be a freq. I wish I could disable the alarm but since the rpms aren't connected it shows random values and everytime it hits zero it sets off the alarms.

I think I'm just gonna sell these things as I don't use the temp monitoring as much as I thought I would.