Got myself a free scope. Have questions.

[Jckf]

Hello, fellows. I recently got my first oscilloscope for free from a guy in my local hackerspace! It's a Kenwood CS-1045 2 ch. 40 MHz analoge scope, and it appears to be in 100% working order The only question I have (so far) is whether or not the calibration is still good. It has an integrated 1 kHz generator, and when hooked up to it and set to 1v/0.5ms per division, the attached image is what I see. Shouldn't each duty cycle correspond to exactly 2 divisions?



EDIT: Oh, one more thing! Does anyone have the service manual for this?

EDIT 2: Figured it out! The red knob together with the sweep time adjustments is for calibration

[tggzzz]

The purpose of the 1kHz square wave is to allow you to tweak the compensation of *10 probes. The frequency and amplitude are relatively unimportant - all that matters is that the transitions are smooth, fast, and there is no over/undershoot.

Don't use it to calibrate the voltage nor time.

[radhaz]

https://www.eevblog.com/forum/beginners/oscilloscope-training-class-%28long%29/

[Jckf]

This is how it looks now:

The purpose of the 1kHz square wave is to allow you to tweak the compensation of *10 probes. The frequency and amplitude are relatively unimportant - all that matters is that the transitions are smooth, fast, and there is no over/undershoot.

Don't use it to calibrate the voltage nor time.

Exactly why is this a bad thing?

https://www.eevblog.com/forum/beginners/oscilloscope-training-class-%28long%29/

Thank you. I will watch this

[tautech]

The purpose of the 1kHz square wave is to allow you to tweak the compensation of *10 probes.

Don't use it to calibrate the voltage nor time.

Exactly why is this a bad thing?

The Cal output is neither precise or accurate enough for scope timebase or amplitude adjustments.
In your case it represents only 1/40,000^th of the bandwidth of your scope.

As tggzzz says it is only intended for adjustment of probes.

BTW good score on the free scope.

[TerraHertz]

EDIT 2: Figure it out! The red knob together with the sweep time adjustments is for calibration

Err, no it's not. The red knob has a detent position all the way clockwise. At that position the timebase is supposed to be calibrated. Same for the channel gain red knobs.
Any other position, is variable, ie the scope timebase/gain is uncalibrated. It's useful for lining up traces with the graticule to judge proportional amplitudes of waveform features. But in 'uncal' mode you can't use the graticule to measure absolute amplitude/time.

For accurate calibration, you need an external known signal. As mentioned by others that 'cal' output is really only for adjusting probe compensation.

Nice scope btw. Have fun!

[Jckf]

The Cal output is neither precise or accurate enough for scope timebase or amplitude adjustments.
In your case it represents only 1/40,000^th of the bandwidth of your scope.

As tggzzz says it is only intended for adjustment of probes.

BTW good score on the free scope.

Of course. This makes a lot of sense. I guess the manual will tell me exactly what I need to know.

Err, no it's not. The red knob has a detent position all the way clockwise. At that position the timebase is supposed to be calibrated. Same for the channel gain red knobs.
Any other position, is variable, ie the scope timebase/gain is uncalibrated. It's useful for lining up traces with the graticule to judge proportional amplitudes of waveform features. But in 'uncal' mode you can't use the graticule to measure absolute amplitude/time.

For accurate calibration, you need an external known signal. As mentioned by others that 'cal' output is really only for adjusting probe compensation.

Nice scope btw. Have fun!

I thought having the calibration on the front of the scope was weird, and the knob snaps into position all the way to the right, just as you describe, which made we wonder.

EDIT: I have probed an external signal, and found that the calibration is spot on! This must mean that the generator in the scope is really bad!

EDIT 2: Looks like the 1 kHz generator in the scope is closer to 930 Hz

[Rigby]

Sounds about right to me.  I've never seen a probe compensation signal that was right OK 1kHz.

[PaulAm]

The Tek 454 (and 453) had a calibration adjustment for calibrator frequency, but not amplitude.  That's the only one I know of that did that.  Most Tek scopes had an internal amplitude adjustment so you could set the calibrator output to a known value.  That way you could do a sanity check on your probe, as well as compensation adjustment.  Many Tek scopes also provided a current  calibration so you could check a current probe with a more or less known current source.

But timing reference?  If they're within +/- 100 Hz that's in the ballpark.  The calibrator circuits are generally pretty simple oscillators or multivibrators.

[tautech]

The Tek 454 (and 453) had a calibration adjustment for calibrator frequency, but not amplitude.  That's the only one I know of that did that.  Most Tek scopes had an internal amplitude adjustment so you could set the calibrator output to a known value.  That way you could do a sanity check on your probe, as well as compensation adjustment.  Many Tek scopes also provided a current  calibration so you could check a current probe with a more or less known current source.

But timing reference?  If they're within +/- 100 Hz that's in the ballpark.  The calibrator circuits are generally pretty simple oscillators or multivibrators.

On the scopes I have fixed, I have always endeavoured to get the Cal output as close as possible to spec with another scope WHEN internal adjustment allows it.
Many old scopes allowed for both  Frequency & Amplitude to be adjusted and others only one.
It just makes sense to have them both close for sanity's sake IMO.

[vk6zgo]

EDIT 2: Figure it out! The red knob together with the sweep time adjustments is for calibration

Err, no it's not. The red knob has a detent position all the way clockwise. At that position the timebase is supposed to be calibrated. Same for the channel gain red knobs.
Any other position, is variable, ie the scope timebase/gain is uncalibrated. It's useful for lining up traces with the graticule to judge proportional amplitudes of waveform features. But in 'uncal' mode you can't use the graticule to measure absolute amplitude/time.

For accurate calibration, you need an external known signal. As mentioned by others that 'cal' output is really only for adjusting probe compensation.

Nice scope btw. Have fun!

A little further comment on the "Uncalibrated" mode:-

This comes up a lot with people buying their first analog Oscilloscope.

The Uncalibrated setting is,for working Techs,one of the most useful functions of such a 'scope.
As TerraHertz  so correctly points out,it enables us to easily compare amplitudes of different parts of signals.

Say we want to express one voltage as a percentage of another one.:-

We could measure both, then grab a calculator & work it out,--OR--we could adjust the larger one to represent 100% & read percentage directly off the scale.

Many test procedures,particularly in TV Broadcasting used special graticules,either physically placed in front of the screen,or "Projected".
These had "reference points"for both time & amplitude,which rarely coincided with the calibrated settings & had to be set in the "Uncalibrated" position.