Hello,
I suggested using the arm start trigger with two counters on an M series card, since the signals can easily be differentiate with two counters. This is where each pulse, the 100 Hz and 1 Hz, would be input into its own counter. I really did not answer your question on how to differential between the two pulses in one gate, because it cannot be done with the E series.
Or I recommended that you drop the 1 Hz GPS and only measure the 100 Hz against the internal timebase using one counter. Both of these recommendations are using Buffered Period Measurement, which is a type of time measurement.
When you are performing time measurement, the signal source has a known frequency. You are using your knowledge of the timebase frequency to help you measure elapsed time. Using the internal timebase of the counter, you can accurately determine the length of a pulse on the gate (Pulse Width Measurement) or the length between two consecutive falling edges on the gate (Period Measurement), or even the elapsed time between two active edges from two different signals (Two-Signal Edge-Separation – only on M series and 6600 series). Time measurement uses a timebase for the source instead of the signal you are trying to measure. In fact, the only difference between time measurement and simple event counting is the signal that is used for the source. The following formula is used to calculate the elapsed time: Elapsed time = (count register value) x (timebase period) where timebase period = 1/timebase frequency
If you are interested in using one gate with an M series, explore the Two-Signal Edge-Separation. However, read the Knowledge Base linked below for details and warnings. Please note that since your two external signals are of different frequencies, I would not recommend this setup. In summary, I would recommend measuring just the 100 Hz with one counter on the E series or using two counters with an arm start on the M series.
You mentioned interest in using a counter input in encoder mode. This is a position measurement type of counter input. When using the Z indexing it is specific to a physical encode setup ... the Z index will reload the counter to start at zero, however the Z line will reset only when Z is high and it correlate to a specific phase of the A and B lines. I do not think this will work with your application. Please research Z indexing if you would like.
AE KB 25SAQQYF: Buffered Two-Signal Edge Separation Measurement with Multiple GATE Edges
Samantha
National Instruments
Applications Engineer
