Modern digital oscilloscopes question

Half again the price of a comparable Rigol, ISTM.

Cheers

Phil Hobbs

"eatmorepies"

If you like using analogue scopes, stick with one.

Analogue scopes are easy to use and tell you no lies.

The opposite is true for digital ones.

... Phil

UNI-T is nice for a Chinese brand. You are aware that the basic 25Mhz model is only good to about 5Mhz for digital (a 5Mhz square wave being made up of a 5Mhz fundamental plus odd order harmonics. 25Mhz only allows the first two harmonics, giving you a wonky square wave but it is OK for basic stuff if you know what your looking for)

Lots of people like this scope:

Have a look at these. They seem to meet your spec and give a bit more.

My regular scope is a Rigol DS1052E. It's great. The going price is around $340.

I'd never go back to an analog scope or a VTVM.

John

Hey, wait a minute. I've bought two Simpson VTVMs in the last year. (Mostly for the nice analogue displays, admittedly. Analogue is nice for temperature-control loops and other things that change on the time scale of 100 ms to 10 s or thereabouts.)

Cheers

Phil Hobbs

I like my Rigol, but to be honest I use the cheap TEK (1001B?) more often.

I've got an old analog TEK that I'd like to bring back to life! Not great speed, but it's got a 1mV/div input range that I used.

DSO's mostly suck at low sensitivity.... JL build's his own input stages, I assume.

George H.

Yeah but an analog 'scope can't average. Put that together with the digital filters on the front end of the Rigol and it's a pretty nice tool for finding signals.

George H.

My TDS744A has a 1 mV/div range, which is still useful at 500 MHz BW. Cost about two low-end Rigols' worth.

Cheers

Phil Hobbs

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Ahh, OK, then most cheap DSo's stink at low sensitivity.

How much for a new one?

George H.

How about a cheap analog scope, supplemented by a ridiculously-cheap (US$29) Windows sound card scope for audio work?

Sound cards don't do DC (without mods or external help), but the "audio" range keeps creeping up... these days you can get to nearly 96 kHz (192 kHz sample rates) even on cheap built-in sound chipsets.

With the proper software (hint, hint!) you can get fancy triggering, including negative trigger delay, hysteresis, hold-off, etc. You can get real-time FFT spectrum analysis (with optional peak tracking), and color spectrograms.

Synchronous waveform averaging allows stupendous noise reduction... you can easily extract signals that were totally buried in noise. See for example:

Best of all, you get a signal generator that can create almost any signal you want, with modulation including AM, FM, PM, Burst, and Sweep on up to 4 independent streams per stereo output channel. It can drive all your tests, and provide the sync for the averaging as well. See:

(Actually, the generator is free. Even if you stick with only an analog scope, or a cheap DSO, you will find plenty of uses for the signal generator.)

Lots of other features, like a frequency counter that can read low frequencies quickly with high precision (due to reciprocal period methods). True RMS measurements. Sound level (SPL) meter (if you have a calibrated microphone). Histograms, including post-stimulus time histograms.

The $99 Pro version allows you to write macros to run automated test sequences, allows custom spectrum response limits for pass/fail production testing, and supports remote control from custom software.

Best regards,

Bob Masta DAQARTA v6.02 Data AcQuisition And Real-Time Analysis

I have an old Tek AM502 diffamp I use to front-end a digital scope. It has switchable hi/lo cutoff frequency, lots of offset range, and tons of CMRR. Gain goes up to 100K.

I think there are some smaller boxes like this around. Somebody (here?) should make an affordable one; it wouldn't be hard, and the Tek specs could be improved with modern parts.

John

I have one of these. Only problem is the 1MHz B/W. Has been useful.though.

I know it isn't tubes, but whaddabout your 610C?

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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That's nice, it'd be hard to beat the $500 price. (At least for me.)

George H.

This has gain of 100, 1 GHz bandwidth.

I scribbled it out as a PCB layout training exercize, but it worked, so we called it a product. We've sold a few.

We make another box that has one input and two outputs, one 10x gain and one 1000x gain, 100 MHz BW, very clean clipping recovery. It's used for looking at low-level junk on a laser pulse, stuff just before and after the main flash.

On a multilayer board, in a box, this stuff usually works. The hard part on the x1000 zoom amp was testing it. Ground loops and RF pickup drove us whacko. We wound up using a battery-powered optical-electrical converter connected right to the input and sending the test signals optically.

John

It does have a needle, so I have to think a little. There's a main range switch and the "x" multiplier above it. Blast from the past.

ftp://jjlarkin.lmi.net/Keithley_1gig.JPG

But it measures 1e-14 amps, so I put up with it.

John

My Model 410 micro-microammeter uses an electrometer tube. It's fun to use, but you have to wait for an hour for it to warm up. (It was $6 plus $25 shipping, and it works perfectly, if your idea of perfect coincides with the peculiarities of a 1965 electrometer.)

Cheers

Phil Hobbs

I still have 2 HP RF volt meters I use, good for 1 ghz that are tubes and has a chopper motor in the back :)

Jamie

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Hmm, All the same gain X BW product. I can only do 10**10 an order of magnitude behind what TEK did ,(about?) 40 years ago? Does anyone do better than 10**11? (all in one small box.) Is there some fundamental 'thing' that sets a limit? (RC?)

George H.