can source and gate used to measure 2 signals using one counter?

[MVK]

I have one PCI 6602 card to measure measure the frequency. PCI 6602 has 10 channels, in which channel 5 and 10 doesn't have 'source' terminal.

• We have to measure frequency from 16 signals using one PCI 6602.
• From channel 1 to 4 and 6 to 9, we have 8 'Gate' and 8 'Source' terminals.
• We have connected 16 signals to these 16 terminals.
• At any given point of the time we want to measure either 'Gate' signals(8) or  'Source' signals(8).

Can any provide any guidance to make a program in labview to measure frequency (period) as per above given points?

Regards

Vijay

[Brooks_C]

Hello Vijay,

It takes one counter for each digital frequency you want to measure and the PCI-6602 has 8 counters total.  This means that the maximum number of digital frequencies you can measure is 8.  If you want to measure 16 frequencies you'll need 16 counters.

Single counter frequency measurements are made by comparing the board's time base (80 MHz) to an external frequency.  The board counts the number of time base periods that occur during one period of your incoming frequency.  When you configure the board to take a single counter frequency measurement the card routes the time base to the source of the counter and then you connect the frequency you want to measure to the gate of the counter.

Here are a couple of articles that explain how these measurements are taken and calculated.  (The second article is on period measurements so for frequency measurements you measure period and take the inverse):

Making Accurate Frequency Measurements

Period Measurements with a Counter

There are example programs available in the LabVIEW example finder.  You can locate these by going to Help>> Find Examples... The examples you want is:  Hardware Input and Output>> DAQmx>> Counter Measurements>> Digital Frequency>> Measure Digital Frequency- Low Freq 1 Ctr.vi.

I hope this explains how counters work and why you need one counter per measurement.

Cheers,