Great test equipment designs

Got pics!

I still use my 610C.

In their day, the HP selective (tuned) voltmeters were cool.

The Tek 547 was the best tube scope. The electron optics were fabulous, and it was a work of art. The plugins did things that are hard to do today.

People plan to put one of my old 547's on a cart, in the lobby of our new place.

My Fluke 8842A DVM is pretty darned good.

Hmm I don't have any sort of relation/experience with many of those. I spent a lot of time with a few PAR 124A lockins. We had a nice General Radio freq synthesizer, can't recall the model number. And of course the PAR/ EG&G 113 preamp is/was a nice tool. (I wish I had on of those on my shelf now.)

George H.

Does the VF display ever cause trouble? It seems that no 8.5 digit meters have VF displays.

Not so far.

We have some HP/Keysight 34460-series DVMs where the VF display drive kicks horrible spikes into the input jacks. The firmware is apparently buggered to hide the noise on the low AC input range; below some level, the display just goes to zero.

LCDs are so cheap, VFs are probably going away.

OLEDs is all I use these days.

Do they wear out the pixels? LED-backlit LCDs seem fine.

Not that I notice, I do have the brightness way down, full brightness is blinding. I have some blue ones, and some yellow / blue ones. After 3 years 24/7 for blue ones those are still fine.

Pro: Lower power consumption than LCD + black light. Faster than LCD. Smaller than LCD, LCD + back light is much thicker. Better viewing angle than LCD !!!! The small ones, like 128x64 are down to just a few dollars now.

Maybe in VERY bright direct sunlight LCD wins for readability. The better OLED viewing angle does it!

Have written a decent library for the small OLEDs by now.

I have a Krohn-Hite tunable filter with plugins. I rarely use it because (weirdly) it has horrible kickout.

Cheers

Phil Hobbs

HP-8640 and HP-8405 are nice. Measurements 59 is uninteresting electrically but superb mechanically. Keithley 610 and Boonton 72BD have never let me down.

My first DMM was the Non Linear Systems LM-3, travelled the world with me. Fond place in my heart and still in occasional use but not quite in the masters' league?

piglet

Dynamic range was more of a concern than noise but we achieved good results for both by building them with PIN diodes as drain or collector "resistors". Worked great. Except it was hard to procure diodes with sufficiently long carrier lifetimes. Got some stories there.

I noticed the "designs by the masters" sections, which

That "Megacycle Meter" is my favorite. The thing is almost EMP-proof.

I rather like the Tek 485. Its 50ohm input isn't merely a 50ohm resistor in parallel with the 1Mohm attenuator - it has a separate 50ohm attenuator.

Plus the blue display is gorgeous and the 350MHz scope triggers on and displays a 1GHz signal (somewhat reduced amplitude, of course!)

OLEDs have a pixel wearout mode as well as possible hard failure.

An electronic instrument is more likely to wear out pixels than a TV set. I remember electroluminescent 7-segment numeric displays: a really bad idea. The most-used segments got dim.

This sounds not ready for prime time:

Some of the early OLEDs would die by themselves even if not used. I bought a tiny little MP3 player for my wife which had an OLED display. She disliked it (the controls were difficult to work) so I stuck it in a drawer. I found it a couple of years later, charged it, and tried to use it, and found that the OLEDs in the display had deteriorated to the point that their glow could only be seen in a darkened room. Even normal room light wiped them out.

I've read that oxygen infiltration into the OLED structure was/is a killer.

Equipment should have a serial readout, so you can still use it if the display breaks.

George H.

I have an 8640, which I had completely refurbished, but it's disappointing compared with, say, a PTS1000.

Measurements 59 is uninteresting > electrically but superb mechanically.

It gives a good clean dip with far weaker coupling than the Heathkit POS I used to have.

Seconded. I have both. The 410 was 20 or so years earlier than the

Nixie tubes?

Cheers

Phil Hobbs

A pity the build quality wasn't in the same league as the 475. They used a lot of nylon parts that dry out and crumble.

Cheers

Phil Hobbs

Or web pages.

I second that. In addition, the dial on mine is quite accurate according to my frequency counter.

I use it frequently to check the self-resonance of inductors, capacitors, and miscellaneous other things (like wires).

A superb instrument.

On a sunny day (Mon, 30 Jul 2018 16:11:01 -0700) it happened John Larkin wrote in :

That makes no sense, displays do not normally on earth know what they are used for?

I remember electroluminescent 7-segment numeric displays: a

I have had it with LG after sort of permanently parking my LG robot vacuum cleaner in some out of the way place. Bad design, useless. OTOH my LG MDISC / bluray burner still works OK. YMMV.

There are cars and cars.

Strange I do not have those problems, 3 years 24/7 test. Even stranger both Samsung and now also Apple use OLEDs in their latest products.

Modern OLEDs are encapsulated it what looks like glass to me.

You could argue that the lifetime of those Samsung and Apple computer products is about as long as their batteries.. So, that for professional equipment it should last longer... OTOH OLED technology will only improve.

I did have lots of bad LCDs, some simply go black if in full sunlight, some stay black... some get bad contacts in the rubber strips, characters fading, many issues. expensive failures, here somebody with an other one just days ago, note the growing black spot in center display:

OLED any time.