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70 Posts
Discussion Starter #1
Son of a.....
=

Here at work, I just had an epiphany, and not the good kind!
=

To correctly measure battery amps, the ammeter shunt should be placed at th=
e end of the string, between the last battery and the controller right?
=

Well the cable that arced on me on the way to last Saturday's "Show 'n Shin=
e" IS the last cable and the shunt is NOT ON IT. Ok, wait a sec....does it =
matter if the shunt is on the positive end or the negative end? I'll double=
-check when I get back to the car. Maybe it's on the positive end of the st=
ring.
=

OMG I'm going to cry if the shunt is in the middle of the pack somewhere. I=
found it in place and just assumed it was correct. I may have been hammeri=
ng my batteries way worse than what the meter shows if this is true!
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Boo!Scare away worms, viruses and so much more! Try Windows Live OneCare!
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70 Posts
Discussion Starter #2
The current in a series circuit is the same throughout the circuit so it do=
es not matter where in the string the shunt is, the reading will be the sam=
e. If being used with an e-meter, the e-meter requires it to be on the neg=
ative end of the pack. This has nothing to do with properly measuring curr=
ent, it is simply an electrical requirement of the meter.

damon
> From: [email protected]
> To: [email protected]
> Date: Thu, 1 Nov 2007 15:21:52 -0400
> Subject: [EVDL] What the [email protected]#$!!
>
>
> Son of a.....
>
> Here at work, I just had an epiphany, and not the good kind!
>
> To correctly measure battery amps, the ammeter shunt should be placed at =
the end of the string, between the last battery and the controller right?
>
> Well the cable that arced on me on the way to last Saturday's "Show 'n Sh=
ine" IS the last cable and the shunt is NOT ON IT. Ok, wait a sec....does i=
t matter if the shunt is on the positive end or the negative end? I'll doub=
le-check when I get back to the car. Maybe it's on the positive end of the =
string.
>
> OMG I'm going to cry if the shunt is in the middle of the pack somewhere.=
I found it in place and just assumed it was correct. I may have been hamme=
ring my batteries way worse than what the meter shows if this is true!
> _________________________________________________________________
> Boo! Scare away worms, viruses and so much more! Try Windows Live OneCare!
> http://onecare.live.com/standard/en-us/purchase/trial.aspx?s_cid=3Dwl_hot=
mailnews
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Windows Live Hotmail and Microsoft Office Outlook =96 together at last. =
Get it now.
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Discussion Starter #3
Ummm I'm confused now. My Electrical mind is a little retro grade, but isn'=
t a meter Shunt supposed to go accross the two terminals of a volt meter, a=
djusted to the voltage measured? And an amp meter has a preset one inthe sa=
me place (internal ususlly) measured to the sensitivty of the meter?
=

Both shunts are very low ohms?
=




Arak Leatham - Web and Desktop Systems Developer




Estimating, Point of Sale, Tracking, Reporting Applications> From: damonhen=
[email protected]> To: [email protected]> Date: Thu, 1 Nov 2007 19:29:09 +0000=
> Subject: Re: [EVDL] What the [email protected]#$!!> > > The current in a series circuit =
is the same throughout the circuit so it does not matter where in the strin=
g the shunt is, the reading will be the same. If being used with an e-meter=
, the e-meter requires it to be on the negative end of the pack. This has n=
othing to do with properly measuring current, it is simply an electrical re=
quirement of the meter.> > damon> > From: [email protected]> > To: [email protected]=
s.sjsu.edu> > Date: Thu, 1 Nov 2007 15:21:52 -0400> > Subject: [EVDL] What =
the [email protected]#$!!> >> >> > Son of a.....> >> > Here at work, I just had an epiphan=
y, and not the good kind!> >> > To correctly measure battery amps, the amme=
ter shunt should be placed at the end of the string, between the last batte=
ry and the controller right?> >> > Well the cable that arced on me on the w=
ay to last Saturday's "Show 'n Shine" IS the last cable and the shunt is NO=
T ON IT. Ok, wait a sec....does it matter if the shunt is on the positive e=
nd or the negative end? I'll double-check when I get back to the car. Maybe=
it's on the positive end of the string.> >> > OMG I'm going to cry if the =
shunt is in the middle of the pack somewhere. I found it in place and just =
assumed it was correct. I may have been hammering my batteries way worse th=
an what the meter shows if this is true!> > _______________________________=
__________________________________> > Boo! Scare away worms, viruses and so=
much more! Try Windows Live OneCare!> > http://onecare.live.com/standard/e=
n-us/purchase/trial.aspx?s_cid=3Dwl_hotmailnews> > ________________________=
_______________________> > For subscription options, see> > http://lists.sj=
su.edu/mailman/listinfo/ev> > _____________________________________________=
____________________> Windows Live Hotmail and Microsoft Office Outlook =96=
together at last. Get it now.> http://office.microsoft.com/en-us/outlook/=
HA102225181033.aspx?pid=3DCL100626971033> > _______________________________=
________________> For subscription options, see> http://lists.sjsu.edu/mail=
man/listinfo/ev
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Discussion Starter #4
>
> Ummm I'm confused now. My Electrical mind is a little retro grade, but
> isn't a meter Shunt supposed to go accross the two terminals of a volt
> meter, adjusted to the voltage measured? And an amp meter has a preset one
> inthe same place (internal ususlly) measured to the sensitivty of the
> meter?
>
> Both shunts are very low ohms?

Umm, huh?

Assuming we are talking about simple analog moving coil meters...

A typical meter movement needs 50mv to move full scale.
For an Amp meter, the shunt is select to produce 50mv when a given current
flows through it (ohms law).
Where the shunt is located in a series circuit is irrelevant because the
current is the same everywhere so the current flowing through the shunt's
resistance will have the same voltage drop anywhere in the circuit.

For a Volt meter you typically use a resistor divider network so that 50mv
flows through the meter when a given voltage is across the network.
The location of the connections HAVE to be at where you want to measure
the voltage.
If you want to measure battery voltage, then the leads must be on each end
of the battery pack.
If you put a voltmeter's leads on either side of your shunt, then all
you'll read is 50mv at max current.

If you are using an E-meter (or similar multifunction meter), it has
specific requirements on connection locations. The e-meter makes
electrical connections between shunt and and battery negative and if the
two points are at different voltage levels (i.e the shunt isn't where it
needs to be) then you can short out something (normally the e-meter)

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Discussion Starter #6
check this out it may help

http://www.allaboutcircuits.com/vol_1/chpt_8/4.html

Rich in Va


----- Original Message -----
From: "Peter VanDerWal" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, November 02, 2007 12:50 AM
Subject: Re: [EVDL] What the [email protected]#$!!


>
>>
>> Ummm I'm confused now. My Electrical mind is a little retro grade, but
>> isn't a meter Shunt supposed to go accross the two terminals of a volt
>> meter, adjusted to the voltage measured? And an amp meter has a preset
>> one
>> inthe same place (internal ususlly) measured to the sensitivty of the
>> meter?
>>
>> Both shunts are very low ohms?
>
> Umm, huh?
>
> Assuming we are talking about simple analog moving coil meters...
>
> A typical meter movement needs 50mv to move full scale.
> For an Amp meter, the shunt is select to produce 50mv when a given current
> flows through it (ohms law).
> Where the shunt is located in a series circuit is irrelevant because the
> current is the same everywhere so the current flowing through the shunt's
> resistance will have the same voltage drop anywhere in the circuit.
>
> For a Volt meter you typically use a resistor divider network so that 50mv
> flows through the meter when a given voltage is across the network.
> The location of the connections HAVE to be at where you want to measure
> the voltage.
> If you want to measure battery voltage, then the leads must be on each end
> of the battery pack.
> If you put a voltmeter's leads on either side of your shunt, then all
> you'll read is 50mv at max current.
>
> If you are using an E-meter (or similar multifunction meter), it has
> specific requirements on connection locations. The e-meter makes
> electrical connections between shunt and and battery negative and if the
> two points are at different voltage levels (i.e the shunt isn't where it
> needs to be) then you can short out something (normally the e-meter)
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.503 / Virus Database: 269.15.17/1103 - Release Date:
> 11/1/2007 6:01 AM
>
>

_______________________________________________
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Registered
Joined
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70 Posts
Discussion Starter #7
You might also like this amp meter...

http://cgi.ebay.com/3-1-2-Red-LED-Digital-AMP-Panel-Meter-Shunt-AC-1000-A_W0QQitemZ270159415056QQihZ017QQcategoryZ73158QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

Rich in Va

----- Original Message -----
From: "torich" <[email protected]>
To: <[email protected]>; "Electric Vehicle Discussion List"
<[email protected]>
Sent: Friday, November 02, 2007 1:31 AM
Subject: Re: [EVDL] What the [email protected]#$!!


> check this out it may help
>
> http://www.allaboutcircuits.com/vol_1/chpt_8/4.html
>
> Rich in Va
>
>
> ----- Original Message -----
> From: "Peter VanDerWal" <[email protected]>
> To: "Electric Vehicle Discussion List" <[email protected]>
> Sent: Friday, November 02, 2007 12:50 AM
> Subject: Re: [EVDL] What the [email protected]#$!!
>
>
>>
>>>
>>> Ummm I'm confused now. My Electrical mind is a little retro grade, but
>>> isn't a meter Shunt supposed to go accross the two terminals of a volt
>>> meter, adjusted to the voltage measured? And an amp meter has a preset
>>> one
>>> inthe same place (internal ususlly) measured to the sensitivty of the
>>> meter?
>>>
>>> Both shunts are very low ohms?
>>
>> Umm, huh?
>>
>> Assuming we are talking about simple analog moving coil meters...
>>
>> A typical meter movement needs 50mv to move full scale.
>> For an Amp meter, the shunt is select to produce 50mv when a given
>> current
>> flows through it (ohms law).
>> Where the shunt is located in a series circuit is irrelevant because the
>> current is the same everywhere so the current flowing through the shunt's
>> resistance will have the same voltage drop anywhere in the circuit.
>>
>> For a Volt meter you typically use a resistor divider network so that
>> 50mv
>> flows through the meter when a given voltage is across the network.
>> The location of the connections HAVE to be at where you want to measure
>> the voltage.
>> If you want to measure battery voltage, then the leads must be on each
>> end
>> of the battery pack.
>> If you put a voltmeter's leads on either side of your shunt, then all
>> you'll read is 50mv at max current.
>>
>> If you are using an E-meter (or similar multifunction meter), it has
>> specific requirements on connection locations. The e-meter makes
>> electrical connections between shunt and and battery negative and if the
>> two points are at different voltage levels (i.e the shunt isn't where it
>> needs to be) then you can short out something (normally the e-meter)
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>>
>>
>> --
>> No virus found in this incoming message.
>> Checked by AVG Free Edition.
>> Version: 7.5.503 / Virus Database: 269.15.17/1103 - Release Date:
>> 11/1/2007 6:01 AM
>>
>>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.503 / Virus Database: 269.15.17/1103 - Release Date:
> 11/1/2007 6:01 AM
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
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