Handheld oscilloscope

[Electronics4you]

Hi there,

I need to buy a new oscilloscope. To me the Velleman PPS10 is perfect because of it's size, but I just have some basic questions about oscilloscopes before.

1) It says in the product brochure that it has a sample rate of 10MS/s. What's that?

2) The maximum bandwith i 2MHz. What happens when I connect it to the 20MHz crystal from a PIC?

3) Can it be used for digital electronics as well as analogue? Volt-measuring, frequency e.a.?

 

[dknguyen]

(1) It means the oscilloscope can sample the input signal at 10 million times per second, or at a frequency of 10MHz. CHeck to see if this is the sampling rate for periodic or aperiodic signals (at least I think that's what the terms where). THe periodic sample rate for a periodic signal will be much higher than for an aperiodic signal.

(2) This means that the oscilloscope will not be able to accurately measure signals that are faster than 2MHz (basically). It will not be able to measure frequency components of signals greater than 2MHz, and will not be able to do a fourier transform for frequency components greater than 2MHz.

(3) It can be used for both digital and analog, as long as the input voltage is not too high (different kinds of probes can step down the reading so that the oscilloscope can handle it). Oscilloscopes can measure voltage, frequency, period, and pretty much every other thing related to votlage like peak, minimum, etc. They cannot measure things like current, resistance, capacitance...

Why don't you just get a desktop oscilloscope? It's probably cheaper and more functional than a portable one. PLus you can't lose it. Do not think of an oscilloscope as a multimeter... or get a hobby one from Parallax or something that costs 1/4 as much, and then save to get a "real" oscilloscope. DO you actually need a portable one? Or do you just want one you can use like a DMM?

COrrect me if I'm wrong, it seems a bit strange to me that a scope can sample at 10MHz, but only has a bandwidth up to 2MHz rather than 5MHz. I can sort of see why, but it's not concrete. I've never given it much thought.

 

[Electronics4you]

Actually it was because I needed a scope that I could use at school. I big one would be a heavy load to move every day, but I can see the point of getting more for a cheaper price. But if it can't measure frequencies higher than 2MHz it's not that good as well. Thanks.

 

[evandude]

if the analog bandwidth is a max of 2MHz, you'll be limited to much less than that for digital signals, because of the harmonics involved. As for your question about a 20MHz PIC crystal, well you're certainly not going to be able to see a 20MHz signal... Due to the sampling rate, at BEST you'd see aliasing, but due to the analog input bandwidth it would probably be entirely filtered out.

Also bear in mind that with only a single input channel you're more limited as to what you can do with it. On a 2-channel scope you can set one channel as a trigger from some output, and use the other channel to monitor your signal of interest at that trigger...

And, also think of how much accuracy you want. With a display of only 128x64 pixels you aren't going to get a great image of a signal, or be able to get any accurate readings from it.

And does it even support FFT? None of the sites I looked it up on seemed to say anything about it.

All in all, I would say that it depends very heavily on what you need out of it. In my opinion, it's little more than a glorified multimeter, and I wouldn't consider it sufficient for most of the tasks I would need an actual oscilloscope for; the advantages of course are cost and portability, but if it doesn't do what you need it to do, then even if it's cheaper it's still a waste...

 

[HarveyH42]

I bought a Hps10 for $129 couple of years ago (surplus). I was working with ultrasonic circuits and needed some indication of the output. Works well enough for what I use it for, which isn't so much for measurement, mostly to view waveforms and signals. Don't know about a bench scope for under $250 that is much better, maybe well used on Ebay.

 

[p3t3rv]

I use a HPS40 i got on ebay from america for only $150 USD simply because i do not have room for a "normal" scope it's definatly no toy

40MHz sampling rate
12MHz analog bandwidth
0.1mV sensitivity
5mV to 20V/div in 12 steps
50ns to 1hour/div time base in 34 steps
full auto set up
adjustable trigger level
X and Y position signal shift
DVM readout
audio power calculation (rms and peak) in 2, 4, 8, 16 & 32 ohm
dBm, dBV, DC, rms ...measurements
signal markers for Volt and Time
frequency readout (through markers)
recorder function (roll mode)
signal storage (2 memories)
high resolution LCD 192x112 pixels
LCD backlight
optical isolated RS232 output for PC

works for me and most people that strugle on without any scope at all would probably say even the HPS10 is more help than nothing at all

 

[mattadler]

I have MS 1280 I have never had any iisue with it I think I paid 300 or so for it I included the spects off the site
DC to 5MHz Bandwidth
20MS/sampling rate
Wave monitoring up to 20MHz by PLL
Single input channel
Graphic Display
- 8 horizontal 4 vertical division
- Text display : Vpp, MIN/MAX V, Freq.
Auto Setup function
Trigger
- Auto and Internal mode
- Slope and 5 levels selectable
Cursor

 

[philba]

You can get 50-60 mhz dual channel portable scopes for around $100 on ebay. I picked up a Tek 2225 for 100 - dual channel 50 mhz portable. It's a bit bulky but not that heavy, a bit over 10 lbs.

I think you will discover that the 2 mhz bw and single channel will limit your usage so much that you will wind up getting a better scope pretty soon.

Frankly, I can't imagine you needing to carry a scope around that much.

If you have access to a PC at school, maybe a USB scope would be a better choice.

 

[mramos1]

If you want small, is the ozi-fox (I think was the name) still around? Cheap, low voltage, my point with this is you will have not problems lugging it around.

Nothing like what you are looking at, but I have a portable OLD Tek 314 that gets me by. I looked at the VELLEMAN. The 40 model is the only one to think about and I would not bite for that price when like Philba said, $100 for a good scope.

It is too bad all the USB scopes are still so expensive, I like the thought of the ICD2 and a scope in my computer bag with the laptop. I can get a PC and flat screen monitor for 1/2 of what the little USB scope module cost. What did I mess there?

And did you see the "make a scope from your sound card websites". And only $30 for the software.

 

[audioguru]

What is wrong with your school that it doesn't have a 'scope for you to use? Ask the principal of the school or ask somebody in government. Go to a local TV station and tell them you have a good story for them about your cheap school. Then you'll get a 'scope pretty quick.

 

[mramos1]

In 1979 when I went to school we had Tek scopes then. Round CRTs on them.

That is a darn good point. What is the name of the school. Want to keep my kids out of there. Because my kids can not touch my scope so the school better have them.