**Date:** Sun, 13 Nov 2005 19:35:23 -0600

**Author:** Stan Dodds

**Subject:** computerized AC circuits

**Post:**

Has anyone tried to do an AC circuits lab exercise with student-grade

data acquisition hardware? I'm having some troubles with the Vernier

LabPro system that seem to be inherent in the design:

1. The maximum real sampling rate is 10,000/second for one probe or

5,000/second with two probes (voltage and current). This limits the

practical frequency range to a kilohertz at best. Automatic fitting of

a sine wave gets flaky even sooner, about 300 Hz, so you have to

eyeball the parameters.

2. The samples are not taken at the same time, presumably because there

is only one sample and hold and one A/D. Understandable in low-cost

equipment, but the channel delay corresponds to a 10 degree phase shift

at 200 Hz. Not good when trying to show the 90 deg shift in a

capacitor.

Is there a work-around you use, or do you explain the quirks to

students without causing utter confusion?

Any help much appreciated.

Thanks

Stan

From dickheckathorn@sbcglobal.net Sun Nov 13 22:37:50 2005