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weird DMM ohms readings on transformer

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Jon Elson
Guest

Tue Dec 31, 2013 6:28 am   



Cydrome Leader wrote:

Quote:
Jon Elson <elson_at_pico-systems.com> wrote:
Cydrome Leader wrote:



What other goofy effects have you seen with these other instruments?
I have a couple Protek meters that I really like. But, the autoranging
can sometimes screw up quite massively. One time, I was checking the
+5 V on a board with some logic. The meter gave an astounding reading
of 125 V or thereabouts! I knew this had to be wildly incorrect as
the circuit was mostly working, rather than exploding in flames.
I locked the range and it gave a somewhat more reasonable reading, but
still quite off. I used another meter and got 5 V on the nose.
Well, the fact the Protek went crazy on this circuit told me there
might be some high frequency noise on the +5, so I added some caps.

That't the most ridiculous reading I've ever gotten from a DVM.

That's pretty impressive. Did it give equally amazing AC readings too?

No, I think the AC mode has a low frequency cutoff, and this was likely
very high frequency noise.

Jon

Fred Abse
Guest

Wed Jan 01, 2014 11:49 pm   



On Sun, 29 Dec 2013 22:06:01 +0000, Baron wrote:

Quote:
Fred Abse scribbled thus:

On Sun, 29 Dec 2013 11:21:06 +0000, Baron wrote:

Come back AVO8, all is forgiven !

I still have one, and it's still within calibration tolerance.


Yup. There's a reason that they are/were industry standards. If I remember
correctly the model 7 was the low Z one, 200 OPV.


Never had a 7. ISTR they were 1000 OPV. Certainly too low for electronics.

I was fortunate enough to get an 8 MKIII, on a trip to England. Bakelite
case, stud-and-leaf switches, and tropicalized resistors. Later models had
thick film resistors and printed circuit switches.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

Baron
Guest

Thu Jan 02, 2014 4:33 am   



Fred Abse scribbled thus:

Quote:
On Sun, 29 Dec 2013 22:06:01 +0000, Baron wrote:

Fred Abse scribbled thus:

On Sun, 29 Dec 2013 11:21:06 +0000, Baron wrote:

Come back AVO8, all is forgiven !

I still have one, and it's still within calibration tolerance.


Yup. There's a reason that they are/were industry standards. If I
remember correctly the model 7 was the low Z one, 200 OPV.

Never had a 7. ISTR they were 1000 OPV. Certainly too low for
electronics.

I was fortunate enough to get an 8 MKIII, on a trip to England.
Bakelite case, stud-and-leaf switches, and tropicalized resistors.
Later models had thick film resistors and printed circuit switches.


Hi Fred, Happy new year.
I used to have a model 7 until it got borrowed. Currently I have two
Model 8, a MKII and MKIII. I did have an ex mill one in a leather
case, that one got stolen when I was burgled. The swine also took my
scope and spectrum analyser along with a lot of other gear.

Never did get any joy from the police, but that's another story.

--
Best Regards:
Baron.

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