doing the r-c test on my 1054z scope - Page 1
Forum section: electronics / beginners

author: 4x1ks
author_rank: Newbie
timestamp: February 14, 2017, 08:24:42 pm
content: Ok, so I've got an instek function generator and the Rigol 1054Z scope...brand new. Can anyone tell me the simplest circuit to use to get that nice rise curve on the scope to measure the 63.2 % capacitance figure? Where to connect the probes and the function generator exactly? What value resistor and cap?Thanksmark

author: rstofer
author_rank: Super Contributor
timestamp: February 14, 2017, 08:37:27 pm
content: 1 kHz square wave into a 6.8k resistor in series with a 10 nF capacitor to common ground.I was doing this very thing last week as part of a calculus demonstration of v(t)=v0(1-e-t/T) where v0is the applied voltage. The calculus part of the deal was to find the inverse function: t in terms of v(t)/v0, a fraction less than or equal to 1.T is tau, the RC time constant and you should show 6 time constants. So, 6.8*103* 10*10-9= 68 uS. Then 68 uS * 6 (tau) -> 408 uS. Figuring both sides of the square wave we need 816 uS or just a little less than 1 mS or about 1 kHz.Still have the breadboard sitting on my bench...

author: fubar.gr
author_rank: Unknown
timestamp: February 14, 2017, 10:38:30 pm
content: You can set up the oscilloscope in Roll Mode, and if you choose sufficiently large values for R and C you can see the capacitor charging in real time!

author: rstofer
author_rank: Super Contributor
timestamp: February 14, 2017, 10:53:18 pm
content: On my breadboard, I connected Ch 1 of the scope to the junction between the resistor and capacitor and Ch 2 to the incoming square wave.You can change the display to just show Ch 1. change the time base to show just one waveform (perhaps only the rising edge) and then use the Cursor feature to bracket timings of interest (like 1 tau).Attached is just an ordinary display like described above. The rest is an exercise...

author: w2aew
author_rank: Super Contributor
timestamp: February 15, 2017, 01:00:48 am
content: I did a video on this a couple of years ago:

author: 4x1ks
author_rank: Newbie
timestamp: February 15, 2017, 10:55:32 am
content: I got it working. The function generator is ok and the scope is great...and much more complicated than my old analog scope. Who says middle-aged guys can't learn things!thanksMark

author: rstofer
author_rank: Super Contributor
timestamp: February 15, 2017, 05:28:00 pm
content: Besides the videos by w2aew (see 'oscilloscope training class' in the stickies at the top of this forum), the Tektronix Arduino program might be of interest.http://www.tek.com/lab-course/learn-digital-oscilloscope-operations-using-arduino-board-dut-signal-generator

author: 4x1ks
author_rank: Newbie
timestamp: February 16, 2017, 08:58:38 pm
content: thanks, I downloaded the course from tektronix. I just need an arduino to work with and I will be able to do the experiments. Looks like a good educational tool. much appreciated.Mark

author: rstofer
author_rank: Super Contributor
timestamp: February 17, 2017, 01:14:17 am
content: It seems to me that the code is dated. I had to make a minor change to get the sine wave project to run:Code:#include "avr/pgmspace.h"#define prog_uchar const unsigned charThe toolchain didn't seem to know what a prog_uchar was. So I added the #define statement. There is some history and a workaround in avr/pgmspace.h I didn't look there before just doing my own workaround.