Measuring peak frequency

[pboyle]

I apologize for the lack of knowledge but I am a very recent user to NI products.

I have a NI 9233 and Signal Express software and I intend to record data from a speed sensor mounted on the shaft of a turbine (the speed probe is a magnetic pickup).  There is one "peak" per rotation so the output will roughly be a sine wave with a frequency equal to the rotating frequency of the turbine.  I wish to measure the maximum rotational frequency of the unit--i.e. the shortest period.  I can do this the hard way which is to look over the time-domain data and find the shortest time between peaks but there must be a better way.  I know that there is a period measuring step that can be added but I am looking for the minimum period.  Can anyone help?

[Brian_R]

The DAQmx driver has built-in functionality to perform this measurement when reading a digital signal.  It sounds like this would be a digital signal that pulses once per rotation.  In SignalExpress, you would click Add Step >> Acquire Signals >> DAQmx Acquire >> Counter Input and then select frequency or period.  You can then keep a running value of shortest period or the highest frequency.  This will require you to have one of the digital input modules (NI-94xx).