Time Measurement

[Mike Boller]

I'd like to measure the time of a capacitor charge curve (0% to 63%).
I just want to measure the time without using an counter device. The
capacitor voltage will be fetched via the RS232-interface and external
measurement electronics.

How can I implement that measurement in LabView 7.0??

Thanks
Mike

[johnsold]

The Pulse Parameters.VI in Analyze>>SignalProcessing>>Time Domain>>Pulse Parameters in LV 6 should do it. The Search Waveform.VI could also be used but would require that you determine the 63% threshold externally. I did not call up LV 7, but I think the same or similar functions are available.

Lynn

[Sean_C.]

Hello Mike,

Thank you for contacting National Instruments.

Another way to do this would be to use the Get Date/Time in Seconds function in LabVIEW to get the time at the beginning of the capacitor charge curve. Then as you read in voltages, compare them to the 63% of total charge. As soon as 63% charge is reached, use another Get Date/Time in Seconds, and from that value subtract the initial time. The result will be the elapsed time in seconds.

I hope this helps,

Sean C.
Applications Engineer
National Instruments

[Dennis_Knutson]

Both of these answers are great but a lot depends on how fast the charge time is and how fast you can actually acquire data from the instrument over the serial port. What's the measurment electronics, what baud rate are you using, what's the expected charge time? If the hardware is inadequate, you won't be able to compensate with software.