Forgive me but I am a little out of my depth here. I have been asked a question about and hand held oscilloscope and my own knowledge extends only to a multimeter at best! I have been left minding the shop for a couple of days and have had an inquiry into whether a certain oscilloscope would measure a 125 kHz signal. My current understanding is that the bandwidth and sampling rate indicate the scopes capabilities in this regard. However I am not sure if a scope has a lower limitation when it comes to frequency? For the sake of clarity I have reproduced the scope's specifications below. I would be grateful of any help.

40 MHz sampling rate

12 MHz analog bandwith

0.1 mV sensitivity

5mV to 20V/div in 12 steps

50ns to 1 hour/div time base in 34 steps

ultra fast full auto set up option

adjustable trigger level

X and Y position signal shift

DVM readout

audio, power calculation (rms and peak)

dBm, dBV, DC, rms ... measurements

signal markers for voltage and time

frequency readout (through markers)

recorder function (roll mode)

signal storage (2 memories)

high-resolution LCD 192x112 pixels

LCD backlight

galvanically separated USB output for PC

data or bitmap download to PC

different screen modes

normal screen view

wide screen with DVM

normal screen with large DVM

wide screen with large DVM

USB PC Connection real-time and screen capture

in the box:

worldwide charging adaptor

insulated measurement probe x1 / x10: PROBE60S

USB cable

Handheld Personal Scope

 

Bandwidth 12Mhz. Shouldn't be a problem at 125kHZ. Scopes will measure to DC also. Just ensure DC coupling is on.

 

Bandwidth 12Mhz. Shouldn't be a problem at 125kHZ. Scopes will measure to DC also. Just ensure DC coupling is on.

Thanks for the reply. Just for my own future enlightenment. What determines the frequency range any oscilloscope can deal with?

 

12 MHz bandwidth means zero to 12 MHz.
I don't think any scope exists that can't do 1 MHz. You can't miss while trying to work with 125 KHz.

What determines the frequency range any oscilloscope can deal with?

The way it's designed and built.
Kind of like, "What determines the speed a car can go?"

 

had an inquiry into whether a certain oscilloscope would measure a 125 kHz signal.

Kindly tell us what kind of signal. Square wave, sine wave, triangle wave, ??? If you're doing audio, a few MHz bandwidth would be more than sufficient.

You made a typo on the sampling rate. It's in Mega Samples Per Second, not Mega Hertz.

For the sake of clarity, you obfuscated the meaningful parameters by including many that have no bearing on bandwidth.

 

40 MHz sampling rate
12 MHz analog bandwith

I think I know what they did. One issue is the Nyquest Creiteria where the sampling rate has to be 2x the sine wave signal of interest. Square waves introduce all sorts of weierdness, because technically a square wave requires infinite bandwidth. Fourier theory says It's composed of the sum of odd harmonic sin waves.

Analog bandwidth is normally cited as the -3db point at when the signal drops to 70.7% of the lowest frequency.
The analog scope may have more "useable" bandwith, but the amplitude isn't accurate above that -3 db point.
I might expect this to be equivalent of a 20 mHz scope, but I'll bet the accuracy specifications are is rated to 12 Mhz.

Here http://www.eetimes.com/document.asp?doc_id=1276244 is a little blurb.

Here http://cp.literature.agilent.com/litweb/pdf/5989-5733EN.pdf is a more complex note.