TDS380 oscolliscope

[robotic]

So I'm thinking of buying a TDS380 scope, it's an auction type sale, so what should my max bid be?  It came from some kind of lab I think.  (unknown when last calibrated).

Is $100 a good deal?

[rustybronco]

$100 would be an excellent price if it was working correctly.

I paid $125 for my TDS360.

[robotic]

any quick way to test a scope?

My thoughts is just to bring in an arduino and let it run some PWM commands and see what it outputs.

I don't think dmm generate waveforms.

[alm]

The obvious thing to check is to see if all self-tests pass. See the manual for how to execute them. For a basic test, connect a probe to each input and check the probe compensation signal. This should show you that it can acquire a signal, that the low frequency response is sane, and you can compare amplitude between the channels. Do not worry about actually compensating the probes or slight differences in probe compensation between channels. You can also try a few attenuator settings within the range of the signal. If the probe compensation output is suspected to be broken, then an external square wave source may be helpful.

To test frequency response you would either need a leveled sine wave oscillator or a clean pulse with a very fast transition time. To test time base accuracy you would need a signal with an accurate and stable frequency. To fully test all attenuator ranges you would need signals with amplitudes ranging from a few mV to tens of volt. So in my opinion verifying more than basic operation of each channel is beyond the scope (no pun intended) of what a quick field test can achieve.

[robotic]

okay found out how to do the self-test.  how do I do the probe thing?

I have never even touched an oscilloscope before, so I have no knowledge.

[alm]

Do you know if it comes with any probes? Do you have anything with a BNC connector (e.g. one of these)? Worst case you can hook a bare wire to the probe compensation output and touch the center of the BNC connectors. Just be careful not to bend the fingers of the connector (touch it, do not shove it in).

Connect the center of the BNC connector to the probe compensation output (you can ignore the ground connection if you do not have a real probe). Then pressing autoset should get you something resembling a square wave on the screen (ignore any distortion if you are not using a proper probe). Then turning the horizontal knob and vertical knob (make sure you have selected the correct channel using the buttons to the right of the screen) should affect the scale (i.e. signal gets wider/narrower/higher/lower). If you feel like it, try to estimate the amplitude of the signal, and compare that between channels (make sure the scale is the same).

[bitseeker]

If you can get temporary access to a scope (e.g., friend, acquaintance, school), try the tests that alm outlined so that you gain some familiarity with how things should look or behave prior to testing an unknown device.

Regarding DMMs with waveform generation, some are able to do that (e.g., Keysight U1252A/B, U1282A). However, the probe compensation signal should be sufficient for confirming basic scope operation (unless, of course, the compensation signal generator is broken).