V. Time varying voltages


Equipment list:
    Dual trace scope
    HP function generator 
    HP-DMM  
    Pasco frequency counters
    BNC T connector
    2 BNC to BNC cables
    1 BNC to banana

Background:
How do you know you are reading your scope voltages and periods with accuracy? Your instructor could tell you but then, you'd have to find him! So being on your own, you need to measure the function generator's output by more than one method and then compare. The instrument you will use to verify your period measurements is a frequency counter. A frequency counter provides a digital output of the frequency of the signal you are measuring. Connect the frequency counter to the "sync" output on your function generator. The sync BNC jack is specifically designed to be connected to a frequency counter. The HP-DMM is designed to measure an AC signal by representing it as an average value, the "RMS" value (root-mean-square). There is a conversion factor allowing you to convert from peak to peak voltage to RMS voltage. That conversion depends on the type of waveform being measured. See your instructor for those derivations.
 

Procedure:
Calibrate your scope to its calibration signal and verify that your scope and leads are working properly.
Your function generator has an output of three different waveforms, sinusoid, triangle, and square. For each different waveform, test two different signals (different in peak-to-peak voltage and frequency) for a total of six different signals. Your scope measurements should be within five percent of the meter readings from the HP-DMM and frequency counter (less than one percent is very good and not uncommon). Your HP-DMM has difficulty sampling frequencies over about 100 kilohertz, so stay well below those values or its reading will be highly inaccurate.
 

Conclusion:
So how close did you get?