http://www.brukerafmprobes.com/a-3480-dafmch.aspx Here is the holder we use for the AFM. We find that one of those four pins is used to apply signal(e.g. voltage) to the tip and normally shorted to the ground. But now we directly connect a wire to the clamp of the holder to send a signal to the tip. But if the pin which is connected to the clamp is