Shunts are available on EBAY occasionally. If you need to make a measurement and cannot wait to get the proper shunt, a reasonable shunt can be patched together with a chunk of wire that can handle the load and a sensitive meter. A meter that will read millivolts is best. The innovative part is how to calibrate the reading. I generally: 1- measure the voltage drop on an existing cable already in the circuit. 2- Add a known load to the measured load & measure again 3- do the arithmetic Don't forget to measure and consider the voltage each time. Hopefully, you will have the ability to measure the load to be added directly. If you find the measurement varying with time you probably are heating the cable you are using as a shunt. Shunts are every where, just look around. A roll of house wiring, a piece of pipe, an auto headlamp(lamps can be tricky), an electric heater, even an aluminum cooking pot! John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "Alan B. Pearce" To: Sent: Thursday, November 21, 2002 8:20 AM Subject: Re: [EE]:Maxim 472 / 4377 Current sense amps > >However my application calls for measuring > 10 amps at > 24v which would require a sense resistor of 5 mOhm. How > >on earth (apart from a pcb track which I don't think > >I will be able to measure or make) do I get 5 mOhm ? > > This sounds like you are into territory where you start with a piece of > copper bar or tube as the sense resistor, and solder (or more likely bolt) a > couple on wires on it at appropriate tap points. > > If you do take this route, then you may need to think about the temp co-eff > of the material used for the bar. If using solid bar, then you can probably > make it in a manner that minimises heat rise due to current flow. > > Personally I would start with a piece of copper 1/2" water pipe, work out > from theoretical resistance of copper how far apart the tap points should > be, and solder a couple of wires on and give it a try. > > Doing things this way also has the advantage that it is almost impossible to > burn out the current shunt :) > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body