Korg Poly800/EX800 Users

Hi friends,

Well, it seems that I may have run into a slight problem with the
backup battery in the HAWK-800 kit. I don't think it's big enough to
do the job since my EX800 had lost its patches (twice) after replacing
the CR2032 battery about 6 weeks apart.

6 weeks is not very good now is it!

So, I had a look at the design and think I might have missed a pull
down resistor that would reduce the current by about half. I've added
the pull down onto both of the HAWK-800 kits and I guess in about six
weeks I'll know if it made any difference at all.

And then perhaps at some point after that, I'll have an idea as to how
much longer the little CR2032 battery will hold up those two 8K static
RAMs.

My calculations for using the CR2032 are below: I would appreciate
feedback from anyone if they can suggest if I've messed up these
calculations.

A high quality CR2032 battery gives about 230mAh or 230,000uAh.

A single 6264 static RAM in standby mode uses between 2 and 50uA.

So two static RAMs will pull between 4 and 100uA.

Therefore, the range of the battery life at 4uA pull should be 2,395
days or 6.5 years (I think this might exceed its shelf life).

At 100uA the life should be 95 days or a little over 3 months.

If we take the middle ground then at 50uA the life should be 191 days
or about 6.5 months.

Now, no matter how I look at it, this just doesn't look very good.

The longer term solution is now being looked at. There are two ways to
go about this. One way would be to use a rechargeable battery
scenario. The other, would be to write patches into flash memory. I'll
post again as soon as I come up with a solution.

In the meantime, BACKUP YOUR PATCHES, and do let me know how long your
patches last before you have to replace the CR2032.

Mike.

On Tue, 27 May 2008, korgpolyex800 wrote:

> So, I had a look at the design and think I might have missed a pull down
> resistor that would reduce the current by about half. I've added the
> pull down onto both of the HAWK-800 kits and I guess in about six weeks
> I'll know if it made any difference at all.

=================

do you have a multi-meter? measure how much current is moving through the
battery...

> A single 6264 static RAM in standby mode uses between 2 and 50uA.

==============

that's a big range... what determines the actual current?

> The longer term solution is now being looked at. There are two ways to
> go about this. One way would be to use a rechargeable battery scenario.
> The other, would be to write patches into flash memory. I'll post again
> as soon as I come up with a solution.

================

a slightly larger rechargeable battery (1/3 AA) would have a better
amp-hour rating, and would last longer than a 2032. i've seen gear with
original 10-15 year old lithium batteries running strong.


--
...atom

________________________
http://atom.smasher.org/
762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
-------------------------------------------------

"In peace, sons bury their fathers.
In war, fathers bury their sons."
-- Herodotus

--- In korgpolyex@yahoogroups.com, Atom Smasher <atom@...> wrote:

>
> > a slightly larger rechargeable battery (1/3 AA) would have a better
> amp-hour rating, and would last longer than a 2032.

I don't know what a 1/3 AA is, but if its one of those weird formats,
please reconsider! I don't understand why you'd be using a 2032
anyway. a triple or double A would last a lot longer and would be
cheaper and easier to source than watch batteries, weirdo cellphone
batteries, etc. The only place I can get reasonably priced 2032s is
the dollar store, and I'm not exactly confident in their quality.

--- In korgpolyex@yahoogroups.com, "zoinky420" <zoinky420@...> wrote:

>
> --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> >
> > > a slightly larger rechargeable battery (1/3 AA) would have a

better

> > amp-hour rating, and would last longer than a 2032.
>
> I don't know what a 1/3 AA is, but if its one of those weird formats,
> please reconsider! I don't understand why you'd be using a 2032
> anyway. a triple or double A would last a lot longer and would be
> cheaper and easier to source than watch batteries, weirdo cellphone
> batteries, etc. The only place I can get reasonably priced 2032s is
> the dollar store, and I'm not exactly confident in their quality.
>

Actually now that I think about it, if you don't use a double or triple
A battery I'm just going to replace whatever you do use with one, so I
guess it doesn't really matter to me one way or another!

Hi Atom,

I will see if I can measure the current but at low current draws the
meter may not be entirely accurate. I'll give it a go though.

According to the datasheet, if I take CS1 high or CS2 low before the
power supply drops from 5V to battery 3V, then the current draw will
be 2uA (typical) up to 100uA (max). But the datasheet seems a bit non
specific about the timing of the chip select lines being at correct
levels prior to the supply dropping to 3V.

So I have a couple of theories as to why the battery is going flat
fast. First, the CS2 chip select line was not being pulled down to 0V.
I've placed a 10K pull down on that line. I am hoping that this, easy
to install, extra resistor will fix the problem.

Second, perhaps the timing of the shutdown of power from 5V to 3V (on
battery) is critical. If that is the case, then I can see a situation
where the chip select lines could be in the wrong state when the power
down occurs. In that circumstance, the battery will pull alot more
current while on battery. As I said though, the datasheet is doesn't
explain the timing very well. Nevertheless, if the one pull down
resistor doesn't fix the problem then I'll add a capacitor on the 3V
battery side of the power supply to the two static RAMs. This will
ensure that the chip select lines settle into their correct state long
before the memory power supply falls from 5 to 3V.

So I don't think this is a big problem, it is just going to take a
while to work out exactly what has to be done. I am hoping that the
single 10K ohm pull down resistor is all that is needed.

Zoinky makes a good point though. The button cell most certainly can
be replaced by two AA batteries. I like the button cell because it's
guaranteed not to leak all over the insides of your precious synth's.

I cringe thinking about the number of Poly's that have been sitting in
storage with batteries slowly decomposing all of the PCB's. I bought
one on ebay specifically because the case, joystick etc was in perfect
condition while the insides were completely acid wrecked.

I think the button cell should be OK in the long run. It is just going
to take a few months to be certain that it is set up just right. And I
wanted to warn everyone before they lose their patches.

Mike.

--- In korgpolyex@yahoogroups.com, Atom Smasher <atom@...> wrote:
>
> On Tue, 27 May 2008, korgpolyex800 wrote:
>
> > So, I had a look at the design and think I might have missed a
pull down
> > resistor that would reduce the current by about half. I've added the
> > pull down onto both of the HAWK-800 kits and I guess in about six
weeks
> > I'll know if it made any difference at all.
> =================
>
> do you have a multi-meter? measure how much current is moving
through the
> battery...
>
>
> > A single 6264 static RAM in standby mode uses between 2 and 50uA.
> ==============
>
> that's a big range... what determines the actual current?
>
>
> > The longer term solution is now being looked at. There are two
ways to
> > go about this. One way would be to use a rechargeable battery
scenario.
> > The other, would be to write patches into flash memory. I'll post
again
> > as soon as I come up with a solution.
> ================
>
> a slightly larger rechargeable battery (1/3 AA) would have a better
> amp-hour rating, and would last longer than a 2032. i've seen gear with
> original 10-15 year old lithium batteries running strong.
>
>
> --
> ...atom
>
> ________________________
> http://atom.smasher.org/
> 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> -------------------------------------------------
>
> "In peace, sons bury their fathers.
> In war, fathers bury their sons."
> -- Herodotus
>

Mike,
Button cells are available in larger sizes too. Some of the gear I
have uses a CR2450 which has 620 mAh of storage. I have a problem
with some of the rechargeables especially the NiCad nightmares I've
seen in the Peavey equipment. I replace them with cell phone
batteries mounted in a remote location away from all boards and
switches.
Letting the current settle will help a lot getting to the 2uA state
in these ram chips.
Fran
--- In korgpolyex@yahoogroups.com, "korgpolyex800"
<korgpolyex800@...> wrote:

>
> Hi Atom,
>
> I will see if I can measure the current but at low current draws the
> meter may not be entirely accurate. I'll give it a go though.
>
> According to the datasheet, if I take CS1 high or CS2 low before the
> power supply drops from 5V to battery 3V, then the current draw will
> be 2uA (typical) up to 100uA (max). But the datasheet seems a bit

non

> specific about the timing of the chip select lines being at correct
> levels prior to the supply dropping to 3V.
>
> So I have a couple of theories as to why the battery is going flat
> fast. First, the CS2 chip select line was not being pulled down to

0V.

> I've placed a 10K pull down on that line. I am hoping that this,

easy

> to install, extra resistor will fix the problem.
>
> Second, perhaps the timing of the shutdown of power from 5V to 3V

(on

> battery) is critical. If that is the case, then I can see a

situation

> where the chip select lines could be in the wrong state when the

power

> down occurs. In that circumstance, the battery will pull alot more
> current while on battery. As I said though, the datasheet is doesn't
> explain the timing very well. Nevertheless, if the one pull down
> resistor doesn't fix the problem then I'll add a capacitor on the 3V
> battery side of the power supply to the two static RAMs. This will
> ensure that the chip select lines settle into their correct state

long

> before the memory power supply falls from 5 to 3V.
>
> So I don't think this is a big problem, it is just going to take a
> while to work out exactly what has to be done. I am hoping that the
> single 10K ohm pull down resistor is all that is needed.
>
> Zoinky makes a good point though. The button cell most certainly can
> be replaced by two AA batteries. I like the button cell because it's
> guaranteed not to leak all over the insides of your precious

synth's.

>
> I cringe thinking about the number of Poly's that have been sitting

in

> storage with batteries slowly decomposing all of the PCB's. I bought
> one on ebay specifically because the case, joystick etc was in

perfect

> condition while the insides were completely acid wrecked.
>
> I think the button cell should be OK in the long run. It is just

going

> to take a few months to be certain that it is set up just right.

And I

> wanted to warn everyone before they lose their patches.
>
> Mike.
>
> --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> >
> > On Tue, 27 May 2008, korgpolyex800 wrote:
> >
> > > So, I had a look at the design and think I might have missed a
> pull down
> > > resistor that would reduce the current by about half. I've

added the

> > > pull down onto both of the HAWK-800 kits and I guess in about

six

> weeks
> > > I'll know if it made any difference at all.
> > =================
> >
> > do you have a multi-meter? measure how much current is moving
> through the
> > battery...
> >
> >
> > > A single 6264 static RAM in standby mode uses between 2 and

50uA.

> > ==============
> >
> > that's a big range... what determines the actual current?
> >
> >
> > > The longer term solution is now being looked at. There are two
> ways to
> > > go about this. One way would be to use a rechargeable battery
> scenario.
> > > The other, would be to write patches into flash memory. I'll

post

> again
> > > as soon as I come up with a solution.
> > ================
> >
> > a slightly larger rechargeable battery (1/3 AA) would have a

better

> > amp-hour rating, and would last longer than a 2032. i've seen

gear with

> > original 10-15 year old lithium batteries running strong.
> >
> >
> > --
> > ...atom
> >
> > ________________________
> > http://atom.smasher.org/
> > 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> > -------------------------------------------------
> >
> > "In peace, sons bury their fathers.
> > In war, fathers bury their sons."
> > -- Herodotus
> >
>

Fran,

What do mean by "Letting the current settle will help a lot getting to
the 2uA state in these ram chips." ?

I am not following what you're saying.

Mike.

--- In korgpolyex@yahoogroups.com, "narfman96" <narfman96@...> wrote:
>
> Mike,
> Button cells are available in larger sizes too. Some of the gear I
> have uses a CR2450 which has 620 mAh of storage. I have a problem
> with some of the rechargeables especially the NiCad nightmares I've
> seen in the Peavey equipment. I replace them with cell phone
> batteries mounted in a remote location away from all boards and
> switches.
> Letting the current settle will help a lot getting to the 2uA state
> in these ram chips.
> Fran
> --- In korgpolyex@yahoogroups.com, "korgpolyex800"
> <korgpolyex800@> wrote:
> >
> > Hi Atom,
> >
> > I will see if I can measure the current but at low current draws the
> > meter may not be entirely accurate. I'll give it a go though.
> >
> > According to the datasheet, if I take CS1 high or CS2 low before the
> > power supply drops from 5V to battery 3V, then the current draw will
> > be 2uA (typical) up to 100uA (max). But the datasheet seems a bit
> non
> > specific about the timing of the chip select lines being at correct
> > levels prior to the supply dropping to 3V.
> >
> > So I have a couple of theories as to why the battery is going flat
> > fast. First, the CS2 chip select line was not being pulled down to
> 0V.
> > I've placed a 10K pull down on that line. I am hoping that this,
> easy
> > to install, extra resistor will fix the problem.
> >
> > Second, perhaps the timing of the shutdown of power from 5V to 3V
> (on
> > battery) is critical. If that is the case, then I can see a
> situation
> > where the chip select lines could be in the wrong state when the
> power
> > down occurs. In that circumstance, the battery will pull alot more
> > current while on battery. As I said though, the datasheet is doesn't
> > explain the timing very well. Nevertheless, if the one pull down
> > resistor doesn't fix the problem then I'll add a capacitor on the 3V
> > battery side of the power supply to the two static RAMs. This will
> > ensure that the chip select lines settle into their correct state
> long
> > before the memory power supply falls from 5 to 3V.
> >
> > So I don't think this is a big problem, it is just going to take a
> > while to work out exactly what has to be done. I am hoping that the
> > single 10K ohm pull down resistor is all that is needed.
> >
> > Zoinky makes a good point though. The button cell most certainly can
> > be replaced by two AA batteries. I like the button cell because it's
> > guaranteed not to leak all over the insides of your precious
> synth's.
> >
> > I cringe thinking about the number of Poly's that have been sitting
> in
> > storage with batteries slowly decomposing all of the PCB's. I bought
> > one on ebay specifically because the case, joystick etc was in
> perfect
> > condition while the insides were completely acid wrecked.
> >
> > I think the button cell should be OK in the long run. It is just
> going
> > to take a few months to be certain that it is set up just right.
> And I
> > wanted to warn everyone before they lose their patches.
> >
> > Mike.
> >
> > --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> > >
> > > On Tue, 27 May 2008, korgpolyex800 wrote:
> > >
> > > > So, I had a look at the design and think I might have missed a
> > pull down
> > > > resistor that would reduce the current by about half. I've
> added the
> > > > pull down onto both of the HAWK-800 kits and I guess in about
> six
> > weeks
> > > > I'll know if it made any difference at all.
> > > =================
> > >
> > > do you have a multi-meter? measure how much current is moving
> > through the
> > > battery...
> > >
> > >
> > > > A single 6264 static RAM in standby mode uses between 2 and
> 50uA.
> > > ==============
> > >
> > > that's a big range... what determines the actual current?
> > >
> > >
> > > > The longer term solution is now being looked at. There are two
> > ways to
> > > > go about this. One way would be to use a rechargeable battery
> > scenario.
> > > > The other, would be to write patches into flash memory. I'll
> post
> > again
> > > > as soon as I come up with a solution.
> > > ================
> > >
> > > a slightly larger rechargeable battery (1/3 AA) would have a
> better
> > > amp-hour rating, and would last longer than a 2032. i've seen
> gear with
> > > original 10-15 year old lithium batteries running strong.
> > >
> > >
> > > --
> > > ...atom
> > >
> > > ________________________
> > > http://atom.smasher.org/
> > > 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> > > -------------------------------------------------
> > >
> > > "In peace, sons bury their fathers.
> > > In war, fathers bury their sons."
> > > -- Herodotus
> > >
> >
>

On Wed, 28 May 2008, korgpolyex800 wrote:

> I will see if I can measure the current but at low current draws the
> meter may not be entirely accurate. I'll give it a go though.

===========

a good digital meter should be able to measure in the uA range.

> According to the datasheet, if I take CS1 high or CS2 low before the
> power supply drops from 5V to battery 3V, then the current draw will be
> 2uA (typical) up to 100uA (max). But the datasheet seems a bit non
> specific about the timing of the chip select lines being at correct
> levels prior to the supply dropping to 3V.

==============

who makes the chips? try calling their tech info number, and you may be
able to reach a product specialist... then you can ask what factors
determine the current draw, and how to decrease it.

> Zoinky makes a good point though. The button cell most certainly can be
> replaced by two AA batteries. I like the button cell because it's
> guaranteed not to leak all over the insides of your precious synth's.

===============

i've seen coin-cells leak... they just have less "juice" than larger
batteries.

> I cringe thinking about the number of Poly's that have been sitting in
> storage with batteries slowly decomposing all of the PCB's. I bought one
> on ebay specifically because the case, joystick etc was in perfect
> condition while the insides were completely acid wrecked.

================

an acid wreched poly800... you make it sound like that's not good ;)



--
...atom

________________________
http://atom.smasher.org/
762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
-------------------------------------------------

"We hang the petty thieves and appoint
the great ones to public office."
-- Aesop

Hi Atom,

Glad you caught the acid pun. I prefer trance.

Batteries never leak trance over PCB's though.

A good multimeter will usually give you bad measurements when the
current you're measuring is under a millivolt. The resistance in the
leads and in the current shunt within the meter will drop the reading.

I'll give it a go though.

Mike.

--- In korgpolyex@yahoogroups.com, Atom Smasher <atom@...> wrote:
>
> On Wed, 28 May 2008, korgpolyex800 wrote:
>
> > I will see if I can measure the current but at low current draws the
> > meter may not be entirely accurate. I'll give it a go though.
> ===========
>
> a good digital meter should be able to measure in the uA range.
>
>
> > According to the datasheet, if I take CS1 high or CS2 low before the
> > power supply drops from 5V to battery 3V, then the current draw
will be
> > 2uA (typical) up to 100uA (max). But the datasheet seems a bit non
> > specific about the timing of the chip select lines being at correct
> > levels prior to the supply dropping to 3V.
> ==============
>
> who makes the chips? try calling their tech info number, and you may be
> able to reach a product specialist... then you can ask what factors
> determine the current draw, and how to decrease it.
>
>
> > Zoinky makes a good point though. The button cell most certainly
can be
> > replaced by two AA batteries. I like the button cell because it's
> > guaranteed not to leak all over the insides of your precious synth's.
> ===============
>
> i've seen coin-cells leak... they just have less "juice" than larger
> batteries.
>
>
> > I cringe thinking about the number of Poly's that have been
sitting in
> > storage with batteries slowly decomposing all of the PCB's. I
bought one
> > on ebay specifically because the case, joystick etc was in perfect
> > condition while the insides were completely acid wrecked.
> ================
>
> an acid wreched poly800... you make it sound like that's not good ;)
>
>
>
> --
> ...atom
>
> ________________________
> http://atom.smasher.org/
> 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> -------------------------------------------------
>
> "We hang the petty thieves and appoint
> the great ones to public office."
> -- Aesop
>

Sorry I was at work and kinda jumped tracks. I got called to check on
some of our process control gear on the floor. The cap idea on the 3
volt line should give the memory chips time to settle into the sleep
state where they will only draw the minimum rated amount of current.

The only pratical experience I have besides the Peavey DPM's is with
the Roland MT-32 battery backup mod. One way uses expensive DS1210
chips to clamp the memory chip enable line (CE) when the power is
removed. The second solution just backs up the 5 volts with a fast
diode to provide the 3 volts to hold the memory intact. Either way
will provide a glitch free memory backup. The second solution also
provides an easy (and cheap) way to provide the extra voltage needed
to recharge the battery pack so 3.6 volt NiMh batteries from a
cordless phone can be used.

Acid you say??? "Mr Watson, Come here, I want you!"

--- In korgpolyex@yahoogroups.com, "korgpolyex800"
<korgpolyex800@...> wrote:

>
> Fran,
>
> What do mean by "Letting the current settle will help a lot getting

to

> the 2uA state in these ram chips." ?
>
> I am not following what you're saying.
>
> Mike.
>
> --- In korgpolyex@yahoogroups.com, "narfman96" <narfman96@> wrote:
> >
> > Mike,
> > Button cells are available in larger sizes too. Some of the gear

I

> > have uses a CR2450 which has 620 mAh of storage. I have a problem
> > with some of the rechargeables especially the NiCad nightmares

I've

> > seen in the Peavey equipment. I replace them with cell phone
> > batteries mounted in a remote location away from all boards and
> > switches.
> > Letting the current settle will help a lot getting to the 2uA

state

> > in these ram chips.
> > Fran
> > --- In korgpolyex@yahoogroups.com, "korgpolyex800"
> > <korgpolyex800@> wrote:
> > >
> > > Hi Atom,
> > >
> > > I will see if I can measure the current but at low current

draws the

> > > meter may not be entirely accurate. I'll give it a go though.
> > >
> > > According to the datasheet, if I take CS1 high or CS2 low

before the

> > > power supply drops from 5V to battery 3V, then the current draw

will

> > > be 2uA (typical) up to 100uA (max). But the datasheet seems a

bit

> > non
> > > specific about the timing of the chip select lines being at

correct

> > > levels prior to the supply dropping to 3V.
> > >
> > > So I have a couple of theories as to why the battery is going

flat

> > > fast. First, the CS2 chip select line was not being pulled down

to

> > 0V.
> > > I've placed a 10K pull down on that line. I am hoping that

this,

> > easy
> > > to install, extra resistor will fix the problem.
> > >
> > > Second, perhaps the timing of the shutdown of power from 5V to

3V

> > (on
> > > battery) is critical. If that is the case, then I can see a
> > situation
> > > where the chip select lines could be in the wrong state when

the

> > power
> > > down occurs. In that circumstance, the battery will pull alot

more

> > > current while on battery. As I said though, the datasheet is

doesn't

> > > explain the timing very well. Nevertheless, if the one pull down
> > > resistor doesn't fix the problem then I'll add a capacitor on

the 3V

> > > battery side of the power supply to the two static RAMs. This

will

> > > ensure that the chip select lines settle into their correct

state

> > long
> > > before the memory power supply falls from 5 to 3V.
> > >
> > > So I don't think this is a big problem, it is just going to

take a

> > > while to work out exactly what has to be done. I am hoping that

the

> > > single 10K ohm pull down resistor is all that is needed.
> > >
> > > Zoinky makes a good point though. The button cell most

certainly can

> > > be replaced by two AA batteries. I like the button cell because

it's

> > > guaranteed not to leak all over the insides of your precious
> > synth's.
> > >
> > > I cringe thinking about the number of Poly's that have been

sitting

> > in
> > > storage with batteries slowly decomposing all of the PCB's. I

bought

> > > one on ebay specifically because the case, joystick etc was in
> > perfect
> > > condition while the insides were completely acid wrecked.
> > >
> > > I think the button cell should be OK in the long run. It is

just

> > going
> > > to take a few months to be certain that it is set up just

right.

> > And I
> > > wanted to warn everyone before they lose their patches.
> > >
> > > Mike.
> > >
> > > --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> > > >
> > > > On Tue, 27 May 2008, korgpolyex800 wrote:
> > > >
> > > > > So, I had a look at the design and think I might have

missed a

> > > pull down
> > > > > resistor that would reduce the current by about half. I've
> > added the
> > > > > pull down onto both of the HAWK-800 kits and I guess in

about

> > six
> > > weeks
> > > > > I'll know if it made any difference at all.
> > > > =================
> > > >
> > > > do you have a multi-meter? measure how much current is moving
> > > through the
> > > > battery...
> > > >
> > > >
> > > > > A single 6264 static RAM in standby mode uses between 2 and
> > 50uA.
> > > > ==============
> > > >
> > > > that's a big range... what determines the actual current?
> > > >
> > > >
> > > > > The longer term solution is now being looked at. There are

two

> > > ways to
> > > > > go about this. One way would be to use a rechargeable

battery

> > > scenario.
> > > > > The other, would be to write patches into flash memory.

I'll

> > post
> > > again
> > > > > as soon as I come up with a solution.
> > > > ================
> > > >
> > > > a slightly larger rechargeable battery (1/3 AA) would have a
> > better
> > > > amp-hour rating, and would last longer than a 2032. i've seen
> > gear with
> > > > original 10-15 year old lithium batteries running strong.
> > > >
> > > >
> > > > --
> > > > ...atom
> > > >
> > > > ________________________
> > > > http://atom.smasher.org/
> > > > 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> > > > -------------------------------------------------
> > > >
> > > > "In peace, sons bury their fathers.
> > > > In war, fathers bury their sons."
> > > > -- Herodotus
> > > >
> > >
> >
>

On Wed, 28 May 2008, korgpolyex800 wrote:

> A good multimeter will usually give you bad measurements when the
> current you're measuring is under a millivolt. The resistance in the
> leads and in the current shunt within the meter will drop the reading.

===============

mA??

my DMM has a current scale that ranges from (up to) 10A down to 200uA.
sure, the resistance of the leads, the shunt, and also the inductance of
the leads will all lead to an "impure" reading, but you're still applying
battery voltage to the circuit, and the circuit will draw what it draws...
and within a reasonable margin of error you can read that with a good DMM,
down to a little less than 1uA. the 4-100uA range that you're trying to
achieve shouldn't pose a problem, unless you're trying to use an analog
meter, or a $5 special.


--
...atom

________________________
http://atom.smasher.org/
762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
-------------------------------------------------

"Our people have made the mistake of confusing the methods
with the objectives. As long as we agree on objectives,
we should never fall out with each other just because we
believe in different methods or tactics or strategy."
-- Malcolm X