flyadive(at)gmail.com
Guest
|
 Posted: Mon Nov 01, 2010 2:28 pm Post subject: AMP METER & SHUNT |
 |
|
Hi David;
You do not require two shunts. �Only one shunt and a meter capable of reading both�Positive�and Negative current flow. �
If I may, let me describe what a SHUNT is and why it is required.
A SHUNT is�exactly�what the word says it is... "A way around", "To�circumvent" as in a�Shun-pike�- A way around a pike.
Why are there shunts? �It is not�practicable�to manufacture an AMMETER for ever current range required by different applications. �So, there are some basic Ammeters at basic current levels: �100 uA. 1 mA, 100 mA & 1 A.
The SHUNT is placed in�PARALLEL�with the above ammeter(s) to�divert�the HIGH current around the Meter, while allowing the small amount through the meter. �
For example:-
If you wanted to read 10 Amps you may use a 1 Amp Meter with a SHUNT capable of�carrying�9 Amps.
The meter reads 0 to 1 and that would be 0 to 10 Amps with the shunt installed.
How is the value of the shunt determined?
By RESISTANCE.
If the Meter has an internal resistance of say 100 Ohms the Shunt must carry a ratio of (X):
1 Amp is to 100 Ohms �
as
9 Amps is to X Ohms
---> WHY 9 AMPS? �Because since the Shunt is in�Parallel�with the 1 Amp meter ...
1 Amp goes through the meter and 9 amps goes through the shunt. A total of a 10 Amp flow.
100 / 9 = 11.11 Ohms for the SHUNT value.
Now I�arbitrarily�picked 100 Ohms and 1 Amp for the meter.
The real value of the meter would probably be closer to 12 Ohms.
Now, You Can Not just put a DMM across a meter to find the resistance. �Because the DMM would load down the meter and give an incorrect reading. �This would be indicated by a deflection of the ammeter needle. �OF COURSE - If the amperage of the un-shunted meter was high enough there would be less loading of the DMM.
Did this confuse ya? �I could go more in depth if anyone is interested � �
One more NOW - The direction of the current does not mater, NOT to the shunt... Dave, you do NOT need anymore than ONE SHUNT. �The direction ONLY�mater�to the Meter.
OK, DONE - - -�Phew!
--
Barry
[quote][b]
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
