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LM317L 20% out of spec

Interesting that it has separate force and sense pins. It could probably be stabilized in a situation with a high-ESR cap by putting a small value low-ESR cap between the two pins and isolating the sense input with a small value resistor. But a BFC is easier. I notice they suggest film caps for high performance.

Had an interesting situation where some analog anti-aliasing filters were far out of spec- turned out that the hand-soldered SMT film caps had opened up at the end and fanned open, greatly reducing the capacitance. Retrofitted some leaded Panasonic types and all was well. Ceramic caps don't pull that sort of shenannigans.

Reply to
Spehro Pefhany
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On a sunny day (Fri, 05 Oct 2012 14:48:09 -0400) it happened Spehro Pefhany wrote in :

ceramic caps are often very temperature dependent, and also have sometimes high losses compared to poly or whatever else. I avoid ceramic caps everywhere except decouling if I can. AND they are sometimes microphonic to, make sound as well as are sensitive to sound. And tolerances tolerances... Did I mention size? No I did not, so size.

Reply to
Jan Panteltje

Leaded film caps are good medicine for a lot of low-level things. A bit of board vibration can produce a surprising amount of current from a 10 uF X5R.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

At my first job we sometimes had to do piezo tests. Every time one of those heavy electric muni buses rumbled along we had to wait until it was far enough down Beethoven Street. After a while we almost knew their schedule by heart.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

At my first job we sometimes had to do piezo tests. Every time one of those heavy electric muni buses rumbled along we had to wait until it was far enough down Beethoven Street. After a while we almost knew their schedule by heart.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

My tube-style Keithley 405 electrometer has a 300-fA FS range. It takes a couple of hours' warm-up before that scale is usable, but once it's there, it makes a very entertaining demo system for the triboelectric effect in coax. Even with a BNC cap over the end of the cable, bumping it even a little bit pegs the meter.

And that's with the meter properly zeroed, so that shorting the input doesn't move the needle, so it's really triboelectricity and not just V*Delta_C.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

We had a customer not too long ago make an inquire about a RG-62U product that make once in a while. It seems they had a customer that used it for some sort of microphonic application and the recent stock we shipped them wasn't so microphonic any more... Oh well.

Jamie

Reply to
Jamie

pump.)

Mine is Solid State!

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I think it uses some old RCA small-signal mosfets in the front end.

It goes down to 1e-14 amps full-scale. Wonderful gadget.

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--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

I once built a wideband amp (14dB from a two transistor "double feedback" circuit, the kind apparently popular for this sort of task) with a 10uF

1206 X7R coupling the input. A light rap on the board produced obvious oscillations in the output, on the order of 50mV, easily triggering the scope. If I knew the transverse stiffness of 0.031" FR-4, I bet I could even calculate the probably 1/2 wavelength resonance of the thing. Acoustic TDR!

Tim

--
Deep Friar: a very philosophical monk. 
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

do

pump.)

It's actually sort of depressing that you can do better than that with an LMC660 and some Russian 10 gigohm glass encapsulated resistors (two for $8 on eBay). None of that sapphire standoff stuff that Keithley used to do.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

do

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I wonder if you could run a small-signal depletion mosfet at Vg=Vs=Vd to get zero leakage. Maybe Vd:Vs could be a very small AC voltage and Vg would modulate the channel conductance, with a closed-loop bootstrap thing.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

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Sort of a resistive version of a varactor sampling bridge, as in the Philbrick P2. I suspect that the symmetry of the FET would make the effect quadratic near zero bias, though.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

pump.)

it's too bad I didn't know you had an interest for G-ohm r's, we tossed a few new, sealed packages not to long ago. These were HV types used in a pre-existing design dynotron supply.

Company likes to do these house cleanings now and then, lots of good nice stuff gets tossed.

Jamie

Reply to
Jamie

do

pump.)

No worries, they're $4 each on eBay. If you toss any more of those nice Boonton 72s, though, I'd love a couple more.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

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Or just run the d-s voltage at, say, 0.1 volts. The fet runs in its ohmic region.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

do

precision

pump.)

I have some samples of 0805 resistors up to 1T ohms.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

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It would be interesting to know what the boundaries on cleanliness and relative humidity are, if one wants to keep, say, 0.5% accuracy through the life of an instrument. It wouldn't take much damp salty flux residue to blow the error budget.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 
845-480-2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

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I posted an experiment here not too long ago. I made a maximally messy flux-gunked pcb and hung it on my Keithley. It pinned the neeedle on the 1e14 range, for a week or so until I lost interest.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

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Plus another $8 to ship them if I located the ones you are indicating:

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10% tolerance.

There are also these at about $3 each:

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But you have to want 25. 5% tolerance.

Jon

Reply to
Jon Kirwan

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I recall. On the other hand, it might not have done as well in New Orleans or New York in the summer, especially if some assembly technician liked eating potato chips, or cleaned the board with drugstore rubbing alcohol instead of electronic-grade ethanol or IPA. (*) (Rubbing alcohol is enough to destroy the performance of a low-level board.)

Also flux isn't very stable with time. That's why I was wondering about how it does over the lifetime of the instrument.

Cheers

Phil Hobbs

(*) Isopropyl alcohol, not India Pale Ale. Even if it is Saturday, the sun's not even up yet, so it can't possibly be over the yardarm.

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

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