I Met My Old Buddy

[Mechatrommer]

today my colleague asked me to show her how to setup an oscilloscope in my school. so this guy has to show up, so here it is, think i will not see "him" very frequently from time to time now, so take this chance and let me introduce you... my old buddy... before my rigol. while setting it up, i still cannot get it right, esp the reading (horizontal and vertical). still confusing as hell even after 1++ year happy with rigol. if you have seen this species, pls leave your comment.

[dimlow]

Hey, there is more than one button on the rigol you know

[saturation]

Nice old design [ but relatively new make of GW?] analog scope.  I had a similar looking one back in the 1980s!!  By Trio-Kenwood.  5 MHz, I worked it to death; it died 2 years ago and I wonder whether I should repair it or trash it; I went looking for a scope, found Dave's review, found Rigol, and the rest is history. 

[Mechatrommer]

Hey, there is more than one button on the rigol you know

this chap got extra. vert var and swp var. the most bugging mystery for me until now. after having rigol, i started to learn what is ac/dc/gnd/int/ext pretty much everything i learnt backward CAL is not operational anymore, dont know if its broken or is just me dont know how to use it, it just a single metal, no ground like rigol has. even the trigger (pull slope?) is delusive back during the old day. i only can confirm/understand two button very well, ie volt/div and time/div. but with previous mentioned knobs/buttons, i pretty much like tried to tinker everything without having a clue to get the phosphor moving in the scope monitor.

Nice old design [ but relatively new make of GW?] analog scope.  I had a similar looking one back in the 1980s!!  By Trio-Kenwood.  5 MHz, I worked it to death; it died 2 years ago and I wonder whether I should repair it or trash it; I went looking for a scope, found Dave's review, found Rigol, and the rest is history. 

this is 20MHz scope IIRC from the manual. last time i searched the closest brand is GW Instek. but operating it, make me highly doubtfull. i think this is GW'nese no brand name cro. this thing is still working as can be seen in the picture, but bid farewell to this buddy.

[dimlow]

Im guessing pull slope is for falling edge trigger. The vars, i have no idea. I never had an analogue scope!!! well I did when I was about 11, but back then I didnt know what it was for. All the other controls I would have thought are pretty basic.

[tekfan]

The var - variable controls give you an infinitely variable vertical gain or horizontal time base setting. Analog scopes usually have 1-2-5 steps. So 50mV, 100mV, 200mV, 500mV, 1v, 2V, 5V and so on. The variable control allows you to go from let's say 2V/div to 1.5V/div. You won't know the exact value when the variable control is enabled but it's pretty useful when comapring signals. So let's say we have a known good circuit and you're comparing it with a faulty one. You want to see if the signal in the working one matches the faulty one so you set the variable control so that you have exactly let's say 6 divisions of deflection. Then you probe the faulty circuit and if you don't get the same value you know you've got a problem.
I hope I haven't confused you even more
The variable control is also really useful for making rise time measurments on an analog scope.

[Mechatrommer]

hmm i suspect it to be like that. with the absence of CAL output, and no voltage reference, this scope is useless for exact voltage or frequency measurement i think. maybe this is why i still confused with this unit. and yes it is usefull to exact fit the graph exactly to the screen size haha, but we will never know its exact amplitude/frequency reading.

edit: i just noticed the picture above tell what i meant. look at center picture and top right. center = 4div frequency and 3div peak volt, and in the top right image, 2div freq ~2.3div peak. thats the same signal i remember. just by tweaking horz var, it will squeeze the freq from 4 to 2 div, making us think the signal is twice as fast, the same to vert var, it will change the amplitude unknowingly which one is the real value.

[tekfan]

I think i can see a CAL position on the variable controls. If you put the knobs in those positions, the vertical and horizontal scale should be calibrated to the vertical volts/division and horizontal time/division settings.