help...newbie with oscilloscope

[chepot]

hi, I very beginner on electronic.

I just buy an analog oscilloscope (20MHz).
here is some information on scope's manual:
(MAXIMUM INPUT VOLTAGE)
1. 400V (DC+AC peak), AC freq 1KHz or lower
2. when set probe 1:1, max effective readout is 40Vpp (14Vrms at sinewave)
3. when set probe 10:1, max effectiv readout is 400Vpp (40Vrms at sinewave)

input independace: approx 1M ohm // approx 25pf

and there is a caution: " max input voltage must have freq less than 1KHz"....I can't scope my 10KHz 555 timer output?

experts...enlight me :idea:

 

[pauloynski]

It is safe with the 555. The restriction applies only for maximum input voltage, wich is not the case.

 

[chepot]

thanks pouloynsky.

is it also save to probe at 40VDC with 3A current on 30KHz frequency? which probe should I set 1:1 or 10:1 ?

 

[pauloynski]

At 40V and 30kHz you could use both settings. Just choose the one that shows you what you want. If your signal is prone to have some spikes then choose the 10:1 input.

 

[chepot]

thanks for helping me paulo.

 

[chepot]

hi, pauloynski...I hope you can help me again on this.

I try to calibrate my probe.
there is a 2Vp-p on my scope for calibration purpose.
the manual state the I should put my probe to 10x and volt/div to 50mv.
I adjust my probe's compensation trimmer but the result is always over compensation waveform.

something wrong?

 

[teepee]

Hello,

It seems that your manual has little typing error. I think the voltage selector should be adjusted to 500mv/div...

 

[eem2am]

At 40V and 30kHz you could use both settings. Just choose the one that shows you what you want. If your signal is prone to have some spikes then choose the 10:1 input.

I would have thought you want to have it on 1:1 if there are many spikes since the 10:1 will exaggerate the noise spikes more than a 1:1 probe?

 

[eem2am]

regarding the probes at 1:1 ar 10:1.

at 1:1 it means the probe impedance is lower.......so you will be filtering what you are measutring much more than if you use a 10:1 probe.

you could use a 100:1 probe....but that has really high series impedance and so small noise currents will produce higher voltages across it and you will see your signal invaded by noise.

You can use any probe you like, but rememeber that the higher the voltage that you are measuring, the higher the probe ratio should be...because if you shove a 1:1 probe on a too_high voltage then it will draw a lot of current from the circuit-under-test and possibly blow something up in the scope....or blow the scope probe up.....i usually find that it blows up the scope probe

from you first post it looks like the manual says that 40VDC is the limiting voltage for the 1:1 probe...........so i would not recommend scoping 40V with that.

you may have to get the probes datasheet