Equipment for my Little Lab

[analoger]

Hello,

Is there any good quality bench top DC power supply? I've checked several brands such as Tektronix and Rigol, BK Precision, Agilent...but what I'm looking for is a compact device that does not take much space, something close in size to a handheld multimeter.

Also any idea why oscilloscopes are super expensive? Like the one I want is Tektronix MDO4104-6, but it's overpriced I think. Rigol is cheaper but do they match the reliability and quality of Tektronix?

Thanks.

[analoger]

I just came across this one:

http://www.matsusada.com/dc/r4k-36/

What do you think?

[adafruit_support_bill]

That is a nice looking little bench supply. If the price is reasonable, I might be interested in one myself.

Regarding scopes, the premium brands like Tek and Agilent will probably always be a cut above the rest in build quality. But brands like Rigol offer a lot of performance for the money. I have been very happy with my Rigol (DS1102D).

[adafruit_support_mike]

Also any idea why oscilloscopes are super expensive?

An oscilloscope has to be faster and more accurate than the circuit you're trying to measure. If it isn't, you aren't getting information about the circuit under test.. you're getting information about the scope's limits.

You want at least five samples per cycle of the fastest signal you want to measure. If you want to measure circuits moving at 1GHz, you need to sample (accurately) at 5GHz.

Like the one I want is Tektronix MDO4104-6, but it's overpriced I think.

Yeah, that's the kind you mortgage the house for.. but overpriced? No.

It has four analog channels and sixteen digital channels that can read signals moving at 1GHz (5GHz sampling rate), one RF channel that can measure signals up to 6GHz, a built-in spectrum analyzer, is capable of running all those at the same time and in sync with each other, and can read signals that rise from 0v to 1v in 350 picoseconds.

Now, when you get down to basic physics, electrical signals travel at about half the speed of light. At 5GHz, one wavefront is only about 3cm away from the next. Being able to resolve signals to 4mV per volt at that rate is no small trick.

Rigol is cheaper but do they match the reliability and quality of Tektronix?

No, but that doesn't make them bad.

Tektronics and Aligent are the Rolls Royce and Ferrarri of instrumentation. It's not just that they make top-quality gear, it's that they have a track record of making top-quality gear that spans decades. Scopes like that come with a certificate that traces their calibration history to a recognized standards lab, and when you buy them you budget for a calibration cycle that will keep that paper trail going. The point of buying them is to have documentation that tracks their performance over their whole working lifespan, because that documentation is what allows you to trust the scope. In the worst case, you'd take that documentation to court to prove that your tests were reliable.

Rigol scopes are more like a Honda Civic.. good for everyday use, but you wouldn't want to bet your life on one. The 1052 series are good entry-level scopes. The 1052E is a dual-trace scope that sells for about $350, the 1052D has a 16-channel logic analyzer as well and sells for about $600. They're 'honest' scopes, in the sense that their sampling rate is higher than their rated bandwidth (1GHz sampling rate, 50MHz bandwidth). The ones that don't use what's called 'equivalent time sampling', which is garbage.

[lyndon]

Also, some of the lower end Agilent scopes are rebadged Rigols. I don't remember which ones, but google will help.

You don't need a brand new scope; lots of older analog ones can be found on eBay for a tiny fraction of what they cost new. My "daily driver" is an Tek 35MHz scope that's probably 30 years old. I paid $50 for it from a company that was upgrading their labs.

[analoger]

So my understanding here is just avoid Rigol even if the alternative is a lower end 10s years old equipment from Tek.

[adafruit_support_mike]

So my understanding here is just avoid Rigol even if the alternative is a lower end 10s years old equipment from Tek.

No, the ones to avoid are the no-name USB/pocket scopes that sell for $89.95. Rigol scopes have an unusually good performance-to-price ratio these days, and even the cheapest scope they sell is good bench equipment.

If you can find a 10 year old Tek that still works and costs less than $500, by all means jump on it. To give you a taste of the market though, a *broken* 10-year old Tek can still sell for a few thousand.

If you want cheap-but-good, look for a 30-40 year old Tek analog scope in the 25-50 MHz range. Those go for maybe $25 and are still excellent pieces of kit. To give you an idea of how good they are, one of the great analog circuit designers of recent memory was Jim Williams, a staff scientist for Analog Devices. He had an extensive collection of 1960s-70s Tek analog scopes, and used screenshots from them when writing App Notes (technical infomation on how to get the most out of the devices Analog sells).

Tektronics contacted Williams and offered him anything from their catalog that he wanted for free, no questions asked, if he'd only stop using gear they quit making thirty years ago.

He turned them down.

[john444]

Mr Stone,

You have some interesting hints and tips on your site.
However, you have not updated it for a while.
You seemed to disappear about the time of the last entry.
But, I noticed you back on the Adafruit forum.
Everything ok?

John

With PM down and if you care to reply directly,
I am John at john no-space meek (dot)
(comextra text for spam prevention)

[analoger]

Thanks for information. This helps me on deciding with my limited budget.

[adafruit_support_mike]

You have some interesting hints and tips on your site.
However, you have not updated it for a while.

Yeah, I have trouble balancing 'making stuff', 'blogging about making stuff', 'work and other trivia', and 'sleeping'. I need to finish that gripping discussion of carrier transport in PN junction diodes.

I have more SMT circuits I want to publish, plus new projects to show off.. just made an 8-value sine wave approximator from a 74*168 shift register and a resistor ladder, then extended it to generate quadrature waves. Now I'm working on a differential power amplifier to drive H-bridges so I can use the whole thing as an 8-step microstep driver with stepper motors. It's just a matter of making time to write everything down.

The gap between entries has been on my mind lately, so I'll probably start writing again soon. Knowing that someone out there actually *reads* it gives me more encouragement. Thanks for that, and for the ego boost.

[john444]

Mr. Stone,
Glad to hear you have been 'just busy'.