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resistors in series

resistors in series

2009-10-05 by Guy

I need a 22M resistor, so I solder two 10M's + one 2M in series.
However, when I measure the end terminals, I end up with something like 32M ?
When I measure in the middle *between* the two 10Ms (the 2M comes last), I get about 20M.

Once again, I am puzzled by this illogical behaviour.

_g

Re: resistors in series

2009-10-05 by Loscha

Your typical domestic Multimeter really isn't optimized to measure anything
beyond about 10M in my experience.

As long as your individual amounts add up, you're in the clear.

/Edward
Show quoted textHide quoted text
On Tue, Oct 6, 2009 at 8:47 AM, Guy <guy@...> wrote:

>
>
> I need a 22M resistor, so I solder two 10M's + one 2M in series.
> However, when I measure the end terminals, I end up with something like 32M
> ?
> When I measure in the middle *between* the two 10Ms (the 2M comes last), I
> get about 20M.
>
> Once again, I am puzzled by this illogical behaviour.
>
> _g
>
>
>



--
www.loscha.com


[Non-text portions of this message have been removed]

Re: resistors in series

2009-10-05 by Guy

Yes, that could well be true. It's not a Fluke or anything fancy, but nonetheless not the cheapest one either... Though I get a bit suspicious when I see that it steps (it's not an autorange) from 2M to 20M and then to 200M.

Thanks, Edward.

_g
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, Loscha <loscha@...> wrote:
>
> Your typical domestic Multimeter really isn't optimized to measure anything
> beyond about 10M in my experience.
>
> As long as your individual amounts add up, you're in the clear.
>
> /Edward
>
> On Tue, Oct 6, 2009 at 8:47 AM, Guy <guy@...> wrote:
>
> >
> >
> > I need a 22M resistor, so I solder two 10M's + one 2M in series.
> > However, when I measure the end terminals, I end up with something like 32M
> > ?
> > When I measure in the middle *between* the two 10Ms (the 2M comes last), I
> > get about 20M.
> >
> > Once again, I am puzzled by this illogical behaviour.
> >
> > _g
> >
> >
> >
>
>
>
> --
> www.loscha.com
>
>
> [Non-text portions of this message have been removed]
>

Re: resistors in series

2009-10-05 by Ove Ridé

2009/10/6 Guy <guy@...>
> Yes, that could well be true. It's not a Fluke or anything fancy, but nonetheless not the cheapest one either... Though I get a bit suspicious when I see that it steps (it's not an autorange) from 2M to 20M and then to 200M.
>
> Thanks, Edward.
I don't see how it would matter in your particular case since the
value you get is too high, but it's worth noticing that your hands
offer some resistance as well. If you try to measure eg a 10M resistor
and hold a finger on each probe, your body will form a parallel
resistor with the one you're trying to measure, and will bring down
the value. It doesn't matter for anything <10k but might become very
noticeable at 10M and up. Solution: Only secure the resistor with one
hand don't touch the other side of the resistor with your other hand.

--
/Ove

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Re: resistors in series

2009-10-06 by Guy

I don't understand why you say "it doesn't matter because the value is too high", Ove ? Of course it matters - I need 22M, not 32M.
10M + 10M + 2M in series ought to be (around) 22M...

I measure pre-mounted, and I don't touch anything with my hands; just using the probes.

Not sure what you're trying to say here, Ove ?

_g
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, Ove Ridé <nitro2k01@...> wrote:
>
> 2009/10/6 Guy <guy@...>
> > Yes, that could well be true. It's not a Fluke or anything fancy, but nonetheless not the cheapest one either... Though I get a bit suspicious when I see that it steps (it's not an autorange) from 2M to 20M and then to 200M.
> >
> > Thanks, Edward.

> I don't see how it would matter in your particular case since the
> value you get is too high, but it's worth noticing that your hands
> offer some resistance as well. If you try to measure eg a 10M resistor
> and hold a finger on each probe, your body will form a parallel
> resistor with the one you're trying to measure, and will bring down
> the value. It doesn't matter for anything <10k but might become very
> noticeable at 10M and up. Solution: Only secure the resistor with one
> hand don't touch the other side of the resistor with your other hand.
>
> --
> /Ove
>
> -----BEGIN 2ROT13 MESSAGE-----
> Blog:
> <http://gameboygenius.8bitcollective.com/>
> SKRIVA på Lysator. Ditt Ahrvid-fria alternativ:
> <http://lists.lysator.liu.se/mailman/listinfo/korkek?SKRIVA?>
> Sätt på ett par flipflops, vippa på rumpan
> och gör det här till en minnesvärd sommar!
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>

Re: resistors in series

2009-10-06 by Ove Ridé

2009/10/6 Guy <guy@...>
> I don't understand why you say "it doesn't matter because the value is too high", Ove ? Of course it matters - I need 22M, not 32M.
> 10M + 10M + 2M in series ought to be (around) 22M...
>
> I measure pre-mounted, and I don't touch anything with my hands; just using the probes.
Hello. My point is that if you touch the probes with your fingers, the
value will be too low, and not as in your case, too high, so that's
not likely to be your problem. Still, I wanted to mention it in case
it might be relevant.
As for your actual problem, I'm chiming in with Loscha, guessing that
your problem is that the meter has a problem measuring high resistance
values.

--
/Ove

-----BEGIN 2ROT13 MESSAGE-----
Blog:
<http://gameboygenius.8bitcollective.com/>
SKRIVA på Lysator. Ditt Ahrvid-fria alternativ:
<http://lists.lysator.liu.se/mailman/listinfo/korkek?SKRIVA?>
Sätt på ett par flipflops, vippa på rumpan
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Re: resistors in series

2009-10-06 by Ehud Tamir

I suggest that you check the batteries in your DVM, I've seen more than once that bad batteries, or battery if it's 9V, will create unreliable and wrong readings.
Also, most of DVM's will measure up tp 20Mohms, and anything above would read as OL (overload - overrange).
If you measure the resistors individally and get the right values, then the total is the sum - in this case as you pointed 22M.




________________________________
Show quoted textHide quoted text
From: Ove Ridé <nitro2k01@...>
To: cgs_synth@yahoogroups.com
Sent: Tue, October 6, 2009 7:02:11 PM
Subject: Re: [cgs_synth] Re: resistors in series


2009/10/6 Guy <guy@...>
> I don't understand why you say "it doesn't matter because the value is too high", Ove ? Of course it matters - I need 22M, not 32M.
> 10M + 10M + 2M in series ought to be (around) 22M...
>
> I measure pre-mounted, and I don't touch anything with my hands; just using the probes.
Hello. My point is that if you touch the probes with your fingers, the
value will be too low, and not as in your case, too high, so that's
not likely to be your problem. Still, I wanted to mention it in case
it might be relevant.
As for your actual problem, I'm chiming in with Loscha, guessing that
your problem is that the meter has a problem measuring high resistance
values.

--
/Ove

-----BEGIN 2ROT13 MESSAGE-----
Blog:
<http://gameboygenius.8bitcollective.com/>
SKRIVA på Lysator. Ditt Ahrvid-fria alternativ:
<http://lists. lysator.liu. se/mailman/ listinfo/ korkek?SKRIVA?>
Sätt på ett par flipflops, vippa på rumpan
och gör det här till en minnesvärd sommar!
-----END 2ROT13 MESSAGE-----






[Non-text portions of this message have been removed]

Re: resistors in series

2009-10-06 by Richard Brewster

Something else to try is to measure the three resistors separately.
This approach avoids the upper limit of the DVM. The total will be the
sum of the three.

Richard Brewster
http://pugix.com

Ehud Tamir wrote:
Show quoted textHide quoted text
> I suggest that you check the batteries in your DVM, I've seen more than once that bad batteries, or battery if it's 9V, will create unreliable and wrong readings.
> Also, most of DVM's will measure up tp 20Mohms, and anything above would read as OL (overload - overrange).
> If you measure the resistors individally and get the right values, then the total is the sum - in this case as you pointed 22M.
>
>
>
>
> ________________________________
> From: Ove Ridé <nitro2k01@...>
> To: cgs_synth@yahoogroups.com
> Sent: Tue, October 6, 2009 7:02:11 PM
> Subject: Re: [cgs_synth] Re: resistors in series
>
>
> 2009/10/6 Guy <guy@...>
>
>> I don't understand why you say "it doesn't matter because the value is too high", Ove ? Of course it matters - I need 22M, not 32M.
>> 10M + 10M + 2M in series ought to be (around) 22M...
>>
>> I measure pre-mounted, and I don't touch anything with my hands; just using the probes.
>>
> Hello. My point is that if you touch the probes with your fingers, the
> value will be too low, and not as in your case, too high, so that's
> not likely to be your problem. Still, I wanted to mention it in case
> it might be relevant.
> As for your actual problem, I'm chiming in with Loscha, guessing that
> your problem is that the meter has a problem measuring high resistance
> values.
>
> --
> /Ove
>
> -----BEGIN 2ROT13 MESSAGE-----
> Blog:
> <http://gameboygenius.8bitcollective.com/>
> SKRIVA på Lysator. Ditt Ahrvid-fria alternativ:
> <http://lists. lysator.liu. se/mailman/ listinfo/ korkek?SKRIVA?>
> Sätt på ett par flipflops, vippa på rumpan
> och gör det här till en minnesvärd sommar!
> -----END 2ROT13 MESSAGE-----
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> The CGS Modular Synth home page: http://www.cgs.synth.net/
> Yahoo! Groups Links
>
>
>
>
>

Re: resistors in series

2009-10-09 by Mark Pulver

And the 2M measures as 2M? What's the color banding?

Any chance that the "3" in the 32M reading is actually an over-range
indicator on your meter?

-----
Guy (02:47 PM 10/5/2009) wrote:
Show quoted textHide quoted text
>I need a 22M resistor, so I solder two 10M's + one 2M in series.
>However, when I measure the end terminals, I end up with something like 32M ?
>When I measure in the middle *between* the two 10Ms (the 2M comes last), I
>get about 20M.
>
>Once again, I am puzzled by this illogical behaviour.
>
>_g

Re: resistors in series

2009-10-09 by midiwall

And the 2M measures as 2M? What's the color banding?

Any chance that the "3" in the 32M reading is actually an over-range indicator on your meter?
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, "Guy" <guy@...> wrote:
>
> I need a 22M resistor, so I solder two 10M's + one 2M in series.
> However, when I measure the end terminals, I end up with something like 32M ?
> When I measure in the middle *between* the two 10Ms (the 2M comes last), I get about 20M.
>
> Once again, I am puzzled by this illogical behaviour.
>
> _g

Re: resistors in series

2009-10-09 by cg_synth

Most digital multimeters can't measure over 20M, if even that much.
I often wonder why Serge thought such a miniscule bias current was needed. There's another spot where there is a 1M between the wiper of a pot and one end. I can't see that making a lot of difference either.
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, "Guy" <guy@...> wrote:
>
> I need a 22M resistor, so I solder two 10M's + one 2M in series.
> However, when I measure the end terminals, I end up with something like 32M ?
> When I measure in the middle *between* the two 10Ms (the 2M comes last), I get about 20M.
>
> Once again, I am puzzled by this illogical behaviour.
>
> _g
>

Re: resistors in series

2009-10-09 by Guy

Thanks for all the replies so far, everyone !

Here's a rundown:

- just replaced the DVM's batteries the day before.
- quite sure (like in:100%) that the '3' in '32" is just that: a number three :-)
- the individual resistors do indeed measure correctly (pm).
- I'm beginning to suspect that the "200M" setting on the DVM is a joke; a bit like the speedometer in cars, where every car seems to be able to do 240Km/H.
- I'm also anally retentive in thinking that the color banding on resistors is a joke as well, what with certain manuf's putting green bands on dark green backgrounds et all -- so I often simply measure resistors. Amazing to see how far off certain values can be, even with 1% resistors.

And, Ken, how important is it then to get those particular high values exactly right (in the VCO) ? For instance, would a 20M (instead of 22M) be good too ? (for lesser kludginess)

_g
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, "cg_synth" <sasami@...> wrote:
>
> Most digital multimeters can't measure over 20M, if even that much.
> I often wonder why Serge thought such a miniscule bias current was needed. There's another spot where there is a 1M between the wiper of a pot and one end. I can't see that making a lot of difference either.
>
> --- In cgs_synth@yahoogroups.com, "Guy" <guy@> wrote:
> >
> > I need a 22M resistor, so I solder two 10M's + one 2M in series.
> > However, when I measure the end terminals, I end up with something like 32M ?
> > When I measure in the middle *between* the two 10Ms (the 2M comes last), I get about 20M.
> >
> > Once again, I am puzzled by this illogical behaviour.
> >
> > _g
> >
>

Re: resistors in series

2009-10-09 by sasami@hotkey.net.au

Considering that the original resistors were probably 5%, I wouldn't be too
worried about the difference between 22M and 20M.

Ken
Show quoted textHide quoted text
>Thanks for all the replies so far, everyone !
>
>Here's a rundown:
>
>- just replaced the DVM's batteries the day before.
>- quite sure (like in:100%) that the '3' in '32" is just that: a number
three :-)
>- the individual resistors do indeed measure correctly (pm).
>- I'm beginning to suspect that the "200M" setting on the DVM is a joke; a
bit like the speedometer in cars, where every car seems to be able to do
240Km/H.
>- I'm also anally retentive in thinking that the color banding on resistors
is a joke as well, what with certain manuf's putting green bands on dark
green backgrounds et all -- so I often simply measure resistors. Amazing to
see how far off certain values can be, even with 1% resistors.
>
>And, Ken, how important is it then to get those particular high values
exactly right (in the VCO) ? For instance, would a 20M (instead of 22M) be
good too ? (for lesser kludginess)
>
>_g
>
>
>
>--- In cgs_synth@yahoogroups.com, "cg_synth" <sasami@...> wrote:
>>
>> Most digital multimeters can't measure over 20M, if even that much.
>> I often wonder why Serge thought such a miniscule bias current was
needed. There's another spot where there is a 1M between the wiper of a pot
and one end. I can't see that making a lot of difference either.
>>
>> --- In cgs_synth@yahoogroups.com, "Guy" <guy@> wrote:
>> >
>> > I need a 22M resistor, so I solder two 10M's + one 2M in series.
>> > However, when I measure the end terminals, I end up with something like
32M ?
>> > When I measure in the middle *between* the two 10Ms (the 2M comes
last), I get about 20M.
>> >
>> > Once again, I am puzzled by this illogical behaviour.
>> >
>> > _g
>> >
>>
>
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: resistors in series

2009-10-09 by peng3002

--- In cgs_synth@yahoogroups.com, "Guy" <guy@...> wrote:
Show quoted textHide quoted text
>

> Amazing to see how far off certain values can be, even with 1% resistors.
>


Well...if the resistor is off more than 1%, it is NOT a 1% resistor.


> And, Ken, how important is it then to get those particular high values exactly right (in the VCO) ? For instance, would a 20M (instead of 22M) be good too ? (for lesser kludginess)
>
>

I would think it would be perfectly fine to use a 20M. For 5% resistors:
22M could actually measure between approx. 21M or 23M and still be in spec. A 20M could measure between 19M and 21M.
22M and 20M are practically the same resistor.

Still unsure? Just try it. CGS boards are very easy to desolder components if needed.

I see a 22M at the input pin 3 of the 3900 for the staircase generator. The other end of the 22M is attached to a trimmer wired between +V and 0V. If I were building this, I would simply use a 10M resistor (since that is the highest value I have) and set the trimmer lower.

p.

Re: resistors in series

2009-10-09 by Tony Mowbray

For all high resistance measurement, a higher voltage is required. At
work we work in the hundreds of MegOhm region. The resistance testers we
use, offer several hundred volts across the resistor under test. A DMM
with a 9volt battery cannot compete, nor can it measure with any
accuracy, such large values.

Just my $0.02 worth...

Regards,

Tony Mowbray

------------------------------------------------------------------------
http://www.linkedin.com/in/tonymowbray

Moto Guzzi 1200 Sport '07

VK2AGM



peng3002 wrote:
Show quoted textHide quoted text
>
>
>
>
> --- In cgs_synth@yahoogroups.com <mailto:cgs_synth%40yahoogroups.com>,
> "Guy" <guy@...> wrote:
> >
>
> > Amazing to see how far off certain values can be, even with 1%
> resistors.
> >
>
> Well...if the resistor is off more than 1%, it is NOT a 1% resistor.
>
> > And, Ken, how important is it then to get those particular high
> values exactly right (in the VCO) ? For instance, would a 20M (instead
> of 22M) be good too ? (for lesser kludginess)
> >
> >
>
> I would think it would be perfectly fine to use a 20M. For 5% resistors:
> 22M could actually measure between approx. 21M or 23M and still be in
> spec. A 20M could measure between 19M and 21M.
> 22M and 20M are practically the same resistor.
>
> Still unsure? Just try it. CGS boards are very easy to desolder
> components if needed.
>
> I see a 22M at the input pin 3 of the 3900 for the staircase
> generator. The other end of the 22M is attached to a trimmer wired
> between +V and 0V. If I were building this, I would simply use a 10M
> resistor (since that is the highest value I have) and set the trimmer
> lower.
>
> p.
>
>

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