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Resistance of ammeter caused voltage drop

F

Fred Bloggs

Jan 1, 1970
0
Larry said:
Why, if
you are such a valuable and respected contributor, do you
not help resolve the error you introduced?

Everything you say is worthless trash- and is to be disregarded- you
don't know what you're doing- you are an engineer impersonator and a
sociopathic narcissist. GFOAD.
 
L

Larry Brasfield

Jan 1, 1970
0
message [More invective and refusal to admit clear error cut.]
The answer is still No. Do you imagine it will
change at some magical repetition number?
If so, why? If not, why not stop asking?
 
F

Fred Bloggs

Jan 1, 1970
0
Larry said:
message [More invective and refusal to admit clear error cut.]

The answer is still No. Do you imagine it will
change at some magical repetition number?
If so, why? If not, why not stop asking?

You will be gone soon- it is easy to shoot down every one of your posts-
you are so ignorant and prone to error. Your posts appear to be an
excuse to tell us more about your life experiences, every one of which
seems to be some sort of gloating about exposing someone as vastly
inferior to yourself- you are a true reject, and of no value to USENET.
You can score your "contribution" to this thread as yet another zero-
totally worthless verbiage- mainly because you failed to comprehend the
question- this inability to understand what others have to say is
another symptom of your narcissism- you don't care what they are saying-
they are not in your tightly sealed internal universe. You are a very
sick reject.
 
L

Larry Brasfield

Jan 1, 1970
0
John Fields said:
---
In light of the fact that his power supply might have been capable of
remote sensing and in view of your statement: "I thought the OP would
like a solution utilizing what he mentioned he had on hand." It seems
to me that your "familiarity" with remote sensing supplies would, at
the very least, brought forth the question of his power supply having
that capability and, if it did, a suggestion to use that capability.

I figured if he had a variable supply, he would not be
so concerned about voltage drop. I tend to assume,
until shown otherwise, that people have a modicum of
intelligence and initiative. So it would not occur to me
to ask if he thought of turning his supply up, although
I gave him a subtle hint that such might be possible.

As for the OP's possible possession of a supply with
remote sensing, I tried to concentrate on what he
claimed to have and give him a workable method
within that constraint. A long list of questions about
what else he might have did not seem time effective
for him or me. I spent a short time considering what
supply he had and decided it was likely something
simple, probably hobbiest grade, since he could
not trust its current meter. Then I decided not to
worry about it and take its output as fixed.

If you want to label those judgements as "ignorance",
"lack of familiarity", "rush to judgement", or anything
else from your panoply, be my guest and I hope you
get as much out of it as I do.

In context, my "knew of" clearly refers to my
knowledge or alleged lack thereof. This last
point is getting to be a real sidetrack.
You, though, knowing that such an option might
have been available didn't bring it up either.

That's right, for reasons stated.
---
He probably shouldn't, but that's not what you advised him to do, you
sent him on some wild goose chase to measure this and that and
calculate this and that, when all you had to tell him was to monitor
the voltage at the input of the radio and crank the supply up to make
that voltage go to 7.5V when he was transmitting, LOL!

HaHa. What makes you so sure he had a variable
supply? And that it could be set higher than he had
already set it? The guy comes here wondering what
to do about a few 100mV of supply drop, knows
enough electronics to recognize some issues that
concern him, and I should start asking him if he has
thought about doing the most obvious things that
anybody with the sense he already exhibits would
not need to come here for? LOL indeed! Thanks,
but no thanks. I'll leave the insulting in the capable
hands of you, Fred, and all your invisible friends.
You also wrote:

"You could also put a lower shunt resistor across
your ammeter and calibrate the combination."

which is one of the stupidest things I've ever read. Do you know why
or would you like me to explain it to you while typing through fits of
laughter?

Ok, I'll bite. (But I must say, your stupidity guage
has some strange attributes given our recent chat! ;^)
Be sure you do not let any lack of imagination affect
your notion of how stupid that idea actually is.

[snip]
That may well be true for your stuff. It just goes
to show that your experience, or anybody's, is
limited and does not constrain reality. Maybe,
since those resistors (when they exist) are inside
the supply, you just never noticed them.

....
"Chicanery" is a little much, John. Nobody was
hurt or even sorry it happened. I am sorry that
this is not obvious to you, and that you have to
leap to that kind of unwarranted conclusion.

I should caw here about how few seconds that would
take to find on your own, (assuming you could remember
how to spell my name for a few moments), but seeing as
how you've been such a helper with Google: US 4656416
 
T

Terry Given

Jan 1, 1970
0
[snip]

Clearly its pick-on-Larry O'clock, so here's my 2 cents worth:

I dont like your hat

Cheers
Terry
 
T

Terry Given

Jan 1, 1970
0
Dummy said:
I have a simple setup as below. The ammeter is used to measure the
transmit current of the radio. Power supply has an display of total
current as well.

Power supply (Vin=7.5V)-------ammeter--------- (Vout) radio

When connecting the ammeter, there's a 0.3V voltage drop across the
ammeter before transmitting. During transmit mode, total current as
displayed at ammeter is 1.80A, matched with the power supply current
display. But Vout is measured to be 6.14V only, thus causing the Tx
power to be lower.

Using direct cable connection without ammeter, the current measured is
almost similar, but the Tx power is much more higher. Current is
1.85A. Vout is 7.0V during transmission - a voltage drop of 0.5V.
I guess the ammeter is giving more resistance the the cable.

So I was wondering whether the ammeter should be used to measure any
high current in circuit level if it can cause some voltage drop. The
voltage drop might affect the circuit performance at the subsequent
stage.

Why not stick one of the power supply leads thru the centre of a DCCT
(aka hall effect DC current transducer). Surely everyone has
half-a-dozen of these sitting in their junk box?

Cheers
Terry
 
J

Jim Thompson

Jan 1, 1970
0
[snip]
Why not stick one of the power supply leads thru the centre of a DCCT
(aka hall effect DC current transducer). Surely everyone has
half-a-dozen of these sitting in their junk box?

Cheers
Terry

Oh Woe Is ME! I only have three. (For three phase EC motors :)

...Jim Thompson
 
T

Terry Given

Jan 1, 1970
0
Jim said:
[snip]
Why not stick one of the power supply leads thru the centre of a DCCT
(aka hall effect DC current transducer). Surely everyone has
half-a-dozen of these sitting in their junk box?

Cheers
Terry


Oh Woe Is ME! I only have three. (For three phase EC motors :)

...Jim Thompson

Bad Jim! :{

Alas, all 12 I have are 300A rated, 3x overload.....

I must buy a few smaller ones :)

Cheers
Terry
 
J

Jim Thompson

Jan 1, 1970
0
Jim said:
[snip]
Why not stick one of the power supply leads thru the centre of a DCCT
(aka hall effect DC current transducer). Surely everyone has
half-a-dozen of these sitting in their junk box?

Cheers
Terry


Oh Woe Is ME! I only have three. (For three phase EC motors :)

...Jim Thompson

Bad Jim! :{

Alas, all 12 I have are 300A rated, 3x overload.....

I must buy a few smaller ones :)

Cheers
Terry

Mine are 50A FS.

...Jim Thompson
 
L

Larry Brasfield

Jan 1, 1970
0
Terry Given said:
Clearly its pick-on-Larry O'clock, so here's my 2 cents worth:

I dont like your hat

Ouch! You guys sure know how to pile on. That's
very close to the most damaging blow so far. said:

Thanks, and likewise.
 
T

Terry Given

Jan 1, 1970
0
Larry said:
Ouch! You guys sure know how to pile on. That's



Thanks, and likewise.

What can I say, I'm one of the people my parents warned me about :)

wrt OP, I once had the brilliant idea of incorporating -ve feedback into
a TL431-opto feedback circuit, by placing the LED resistor at the o/p
rail, then taking the o/p voltage feedback from the bottom of that
resistor in order to reduce the maximum gain and stabilise it (Aol is
all over the show for a TL431). OK, fair enough, it ought to work. In
order to test it, I slapped a Fluke87 (in mA mode) in series with the
TL431. The voltage drop across the ammeter was more than enough to screw
up the entire circuit (esp. since it was in the -ve feedback part), and
as I was being particularly thick that day it took several hours for me
to figure out why it didnt work.

Thats not so bad. What really hurt was my tech roaring with laughter
when he found out what I had done, then calling the other guys down for
a laugh. Perhaps it was revenge for the time I kicked him in the ankle
whilst his head was under a shelf - ouch clonk **** OWTTE ;]

Actually it was probably payback for the time I gave him a dish
containing about 10,000 0603 caps (200 values), and asked him to sort
them out. Half an hour later, there he was painstakingly measuring each
one, until one of the other techs took pity on him and told him the
correct response to such a request was "piss off"

Cheers
Terry
 
J

JeffM

Jan 1, 1970
0
Why are you responding to me?
oh no...the thread police
Mark

174 posts to Usenet and you still haven't figured out
context
attribition
threads

Congratulations. You hit the dumb-ass trifecta.
 
R

Rich Grise

Jan 1, 1970
0
Actually it was probably payback for the time I gave him a dish
containing about 10,000 0603 caps (200 values), and asked him to sort
them out. Half an hour later, there he was painstakingly measuring each
one, until one of the other techs took pity on him and told him the
correct response to such a request was "piss off"

Was he getting paid by the hour? ;-)

Cheers!
Rich
 
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