Accurate Current Measurement

Hey all,
Looking for a way to accurately measure low level current running over a power line on my robot (current somewhere between 0.05A and 0.5A). I do not
need it to measure higher values. Current I am using a toroid ring style system but I feel that is more suited to larger current applications (1 - 15A) rather than mine. Any ideas?
TIA
Fr33
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
A small value resistor -- like 0.1 to 1.0 ohm -- can be inserted in line with the incoming power. Measure across the resistor for a voltage...Ohm's Law will tell you the current. Of course, you will need an ADC or comparator input on your controller, but I assume you already have that for the torroid you're presently using.
The resistor should ideally not be wire-wound, and it should be a wattage suitable for the voltage * current drawn through the circuit. A 5 or 10 watt resistor ought to be more than enough for a 5 volt system, at half an amp max.
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
fr335tyl3r

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I normally use a current probe at work, but the resistor I was provided for using the measurment technique Gordon describes is labeled:
Isabellenhutte A-H1-R100-0.1 R04
Hope this helps.
- James B

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.