Is it 0.2 us or 0.2 ms?

PG1995 · Jun 2, 2012

Hi

Kindly help me with the query included in the attachment. Thank you.

Regards
PG

Grossel · Jun 2, 2012

It seems to mee that the scale is splitted at one o clock. When button stays in any position left to the split the readings should be in ms.

But in the other hand, I'm not familiar with the interface, so you should do some testing and see if that looks right to you.

rumpfy · Jun 2, 2012

If you look closely at the scale calibration you will see that the scale calibration starts at 200 mSec and then reduces to 100 then 50 then 20 then 10 then 5 then 2 then 1 then 0.5 then 0.2 then 0.1, and then the scale divides with the grey patch.
This is a common scale factor; ie 1:2:5
At the point where the scale is divided, the mSec side is 0.1. That is 0.1 mSec per cm. This is the same as 100 uSec per cm.. The scale keeps on reducing as one continues to turn the knob clockwise. Based on the scale factor of 1:2:5, the next scan rate should be 50 uSec per cm; which it is.
So to the left of the 1 oclock mark the scale is mSec per cm; to the right of the mark is uSec per cm.
hope this helps.

PG1995 · Jun 3, 2012

Thank you, Grossel, rumpfy.

rumpfy said:
If you look closely at the scale calibration you will see that the scale calibration starts at 200 mSec and then reduces to 100 then 50 then 20 then 10 then 5 then 2 then 1 then 0.5 then 0.2 then 0.1, and then the scale divides with the grey patch.
This is a common scale factor; ie 1:2:5
At the point where the scale is divided, the mSec side is 0.1. That is 0.1 mSec per cm. This is the same as 100 uSec per cm.. The scale keeps on reducing as one continues to turn the knob clockwise. Based on the scale factor of 1:2:5, the next scan rate should be 50 uSec per cm; which it is.
So to the left of the 1 oclock mark the scale is mSec per cm; to the right of the mark is uSec per cm.
hope this helps.

I'm sorry to say this but I'm still confused. I still don't get how to read the scale. There are two dials: one for ms and the other for μs. In the attachment in my last post, ms dial is set at 200 and μs dial is positioned at 0.5, and the result is "0.2". Is that "0.2" in ms or μs? Please help me with it. Thank you.

Regards
PG

ericgibbs · Jun 3, 2012

hi PG,
This circuit you are measuring would give us a clue.

Do you have a circuit diagram to post.?

PG1995 · Jun 3, 2012

Hi Eric

The o-scope screenshot is from the Proteus. I implemented blinking LEDs assembly code for the 8051 using Proteus ISIS.

Code:

;using AT89C51 with XTAL 12 MHz'


org 0x0

	Repeat:
	mov A, #55H
	mov P0, A
	mov P1, A
	mov P2, A
	ACALL Delay  ;ACALL take two bytes - 11 bits are used for address. LCALL takes 3 bytes
		    ;For ACALL target address of subroutine should lie within 2K bytes 

	mov A, #0AAH
	mov P0, A
	mov P1, A
	mov P2, A
	ACALL Delay
	SJMP Repeat

;-------Delay Subroutine

;period of one MC = 0.001 ms
;75(50(255x2x0.001)) = 1912.5 ms = 2 s

	org 0x300

	Delay:
	    mov R0, #75		;1 MC
	L1: mov R1, #50
	L2: mov R2, #255
	L3: DJNZ R2, L3		;2 MC
	    DJNZ R1, L2
	    DJNZ R0, L1 
	    RET			;2 MC

end

ericgibbs · Jun 3, 2012

hi PG,
Working on the assumption that the Sim LED are RED at 2V forward voltage drop and you have NO series current limiting resistors.

The Voltage scales of your scope show a 2 Volts amplitude with the 'konbs' in those positions.

I would therefore say that the Time base is 0.2Secs/graticule, giving an approx period of just under 2 seconds.

PG1995 · Jun 3, 2012

Thanks, Eric.

So, the small μs dial doesn't contribute to anything because bigger ms dial is set at 200 ms which is equivalent to 0.2 sec. So, what should we conclude from this? Should we infer that when μs dial is set at 0.5, then it doesn't play any role? Please let me know. Thank you.

Regards
PG

JimB · Jun 3, 2012

My first recomendation - get a real oscilloscope to learn with, not this computer game. (Others may have different opinions.)

Now to the problem in hand:

The big yellow triangle thing is pointing to 200mS, so I suspect that the horizontal scale is 200mS per division.

Assuming that your computer game is supposed to be a facsimile of a real oscilloscope, the little yellow triangle which is pointing to 0.5μS is actually the "variable" control. So that if you want some intermediate value of timebase speed between the fixed 1, 2, 5 settings of the switch (say 125mS per division) you can set this using the variable control.
Generally with a real oscilloscope, the variable control is set fully clockwise when not required, because fully clockwise is the calibrated position where the switch settings are accurate.

Look at the attached pictures of my old scope.

JimB

PG1995 · Jun 3, 2012

JimB said:
My first recomendation - get a real oscilloscope to learn with, not this computer game. (Others may have different opinions.)

Now to the problem in hand:

The big yellow triangle thing is pointing to 200mS, so I suspect that the horizontal scale is 200mS per division.

Assuming that your computer game is supposed to be a facsimile of a real oscilloscope, the little yellow triangle which is pointing to 0.5μS is actually the "variable" control. So that if you want some intermediate value of timebase speed between the fixed 1, 2, 5 settings of the switch (say 125mS per division) you can set this using the variable control.
Generally with a real oscilloscope, the variable control is set fully clockwise when not required, because fully clockwise is the calibrated position where the switch settings are accurate.

Look at the attached pictures of my old scope.

JimB

Thank you, JimB.

I'm amazed that you have been using that "rusty but trusty" o-scope for the last 40 years! I was gifted a fluorescent toy turtle when I was so little that I don't even remember that moment and I still have it and in the future when I have my own kids, the favorite one them will inherit this from me.

So, when the little yellow triangle dial is set fully clockwise, then the horizontal scale entirely depends on the big yellow triangle dial. How do I get 125 ms value? I mean, where would both dials point to for 125 ms value? Please help me with it. Thank you.

Regards
PG

JimB · Jun 3, 2012

How do I get 125 ms value? I mean, where would both dials point to for 125 ms value?

Set the big yellow triangle to 100mS and then the little yellow triangle to ?? who knows, somewhere anticlockwise from where it is.

This of course assumes that I am correct in interpreting your scope display.

Question, dont you have a "manual" for it, in which case RTFM! (Or should that be RTFPDF?).

JimB

PS, my scope was about 10 years old when I bought it around 1984.

PG1995 · Jun 3, 2012

JimB said:
Set the big yellow triangle to 100mS and then the little yellow triangle to ?? who knows, somewhere anticlockwise from where it is.

This of course assumes that I am correct in interpreting your scope display.

Question, dont you have a "manual" for it, in which case RTFM! (Or should that be RTFPDF?).

JimB

PS, my scope was about 10 years old when I bought it around 1984.

Hi JimB

I have made this video and it might help you to see how the o-scope functions. Thanks.

Regards
PG

JimB · Jun 3, 2012

Yes, I have seen your video, and the little triangle is exactly as I thought, a variable control for the timebase.

The value of mS (or seconds etc) per division is shown in the numerical box below the timebase control.

JimB

PG1995 · Jun 3, 2012

Thank you.

And the manual didn't have that information otherwise why would I start this thread, take screenshots, make video etc?!

Regards
PG

JimB · Jun 3, 2012

Thank you.

You are welcome.

And the manual didn't have that information otherwise why would I start this thread, take screenshots, make video etc?!

Well, there is a lesson for the future, if you ever get into the situation where you have to write user or maintenance manuals, make sure that you include EVERYTHING.

JimB

rumpfy · Jun 3, 2012

To be specific, I think the '0.2' number in green in the window is actually 0.2 seconds; that equals 200 millisec.
I have to say I think my first reply was incomplete and /or confusing.
But based on the position of the knob (200mS) and the display showing '0.2', then according to my logic the 0.2 stands for 0.2 seconds per cm.
You can check this quite easily;
If you connect the input to a power mains voltage, the period of the wave form will be 20 milli sec for a 50 Hz supply (or 16.6 milli sec for a 60 Hz supply).
Jimb does make the point about having the manual(s). I have a bit of an obsession with manuals (and test leads): Cant do without them. Just have a look at the posts where info is requested and the information would be in the manual. Many times I have wanted to buy something and there has been no manual; I walk away. The manual is where the maker has put all his design info for the user.
Hope you get the question resolved.

Is it 0.2 us or 0.2 ms?

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