DSO-8502 Oscilloscope (500 MHz) by Link Instruments

T&E Engineer

I just saw this in Nuts and Volts magazine and thought it had the most capability for the price. Has anyone used this or a similar model? I am ordering some lab equipment for my new Test and Evaluation lab for work. I got approval to purchase this but wanted to hear from others on this. I may not need to use it that often but want to have the capability to test various forms of customers hardware (software too) for National Incident Management Systems (NIMS) standards.

Here is the link:

http://www.link-instruments.com/oscilloscope85.htm


Post Edited (T&E Engineer) : 12/4/2006 1:51:46 AM GMT

pjv

Hi Timothy;

Not to be too critical, because it looks like a reasonable piece of equipment at not a bad price, but your heading references "500 MHz", which would lead one to believe that was the analog bandwidth. The bandwidth in fact is 100 MHz, which is still very nice for a such a unit; it is the sampling rate that is 500 MS/s.

Hope it serves you well when you purchase it.

Cheers,

Peter (pjv)

terahertz

I've used a few types of USB o'scopes, I even own one.

You can find some that are much cheaper, ~$125. I can't say I would recommend one at all, I've never seen one that would trigger consistantly. If you only want to look at low frequecy waveforms once in a while it would be fine. I'd find an online store through Ebay or something and buy a "real" o'scope, used·for $200-$300.

T&E Engineer

Peter,

You are right and it is a bit misleading.

The original link I provided states in its narative:

The DSO-8502 is our newest series of USB 2.0 PC Based Oscilloscope. The DSO-8502 Oscilloscope operates at up to 500 MSa/s (500 MHZ). Other features include a Spectrum Analyzer (FFT), Pulse width and count triggering, Channel History buffers, Pass/Fail testing and many measurements.

High Speed Sampling

• The OScope captures single-shot data at 500MSa/s (every 2ns)
  500MSa/S (500MHz) single shot sample rate on 1 channel with a 1 Million point buffer.
  250MSa/S (250MHz) single shot sample rate on 2 channels with a 512K point buffer.

Deep Acquisition Memory

1 Million point buffer on 1 channel at a sample rate of 500MSa/S (500MHz).
512K point buffer on 2 channels at sample rates of 250MSa/S (250MHz) and below.

This is much longer than standard Oscilloscopes and enables you to capture more waveform details without sacrificing overall recording time. Longer data buffers give you the flexibility to use faster sample rates and still capture for extended periods of time.

However, in its specifications it does state (that I missed):

Bandwidth: 100 MHz+

So it has a sampling rate of 500 MHz but a Bandwidth of 100 MHz. Can someone tell me what the differences are?

Please clarify.

LoopyByteloose

Simply put, you may need 5 samples to make a good number.
Actually I think the rule is at least 2 samples, but 5 is much better, more precise.
I suppose you might squeeze 125mhz without much effort.

Below two samples, you get misinformation.

Is this Nyqust I am referring to?

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T&E Engineer

Thanks Kramer!

That makes sense now. Im used to analog Oscopes so this will be a first for Digital (DSP probably). I think this is a good product and will continue to purchase even at 100 or 125 MHz.

Thanks again.

terahertz

Kramer said...
Is this Nyqust I am referring to?

Yes it is, the Nyquist theorem basicaly states that for digital sampling, the sampling rate must be AT LEAST 2 times the highest frequency component of the sampled waveform. The 2X sampling rate is the mathamatical minimum, in practice it must be higher.

T&E Engineer said...
Bandwidth: 100 MHz+

The OScope captures single-shot data at 500MSa/s (every 2ns)

1 Million point buffer on 1 channel at a sample rate of 500MSa/S (500MHz)

If the sampling rate is 1 sample every 2nS, and BW is 100MHz.·Then 1/100MHz=10nS so it is sampling at a Nyquist rate of 5 at 100MHz, and 10 at 50MHz etc. The one I have allows adjustment of the sampling rate.
But, with a 1 million point buffer, the buffer is filled every 20mS at 100MHz.

The thing is, with these USB o'scopes the closer your measurements are to the·upper limits (100MHz) the less reliable the results, this is due to the oscillators they use which are powered from the 5V line on the USB. If your going to use this for testing customer's products to NIMS standards, just be careful.

metron9

I have the DSO 2102M The previous model, Maximum sample rate 10ns It is the usb model but I use it with the parallel port on my desktop.

I am very satisfied with it, typically I am in the 20mhz to 50mhz area I need to sample. I have 2 computer monitors so I can program on one, upload to chip and keep the DSO screen on the second monitor. You can set the memory sample size at 1K or 32K so at 32K mem and a sample rate or 1ms you get 32 seconds of storage, a one shot sample and you can look at the data in any time frame. At the other side sampeling at 10ns with 1K mem you get 10us of storage.

I guess it has setup for pass fail circuit testing but I have not used that feature.

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Re-arrange what's inside the box then...
Think outside the BOX!

Yendor

There was a few writeups and reviews of usb o-scopes that may help·- check at the bottom of this link of the Parallax USB scope.

http://www.parallax.com/detail.asp?product_id=28119

mainly this one...
http://www.parallax.com/dl/docs/article/EmbScopeUSB.pdf

LSB

I've been eyeing this one recently... http://www.hobbylab.us/USBOscilloscope/Home.htm. Any comments?

CCraig

LSB,

IF, I'm reading the specs on that HobbyLab one correctly, that things is really slow. I think the Parallax scope is better than that one (although no logic analyzer). I have the Parallax one and it's fine for slow stuff. It's amazing actually.

I have promised myself when I upgrade it will be http://www.pctestinstruments.com/ LogicPort for logic analyzer only.

OR

A Pico scope 310 with both, http://www.bitscope.com/ (which has to take a boat ride from Down Under).

More money, I know, but should last a long time.

NOTE: Those are my personal options, your mileage may vary.

HTH, Chris

LSB

I agree; I always seem to end up at Parallax when I consider cost /and/ features. I've been 'stung' enough to realize the value of your advice and the Parallax name; its a Parallax product for me. Perhaps later (when ability and experience necessitates), as you, I'll make a magnatude greater investment.

Thanks for talking me down man!

Mark