[SI-LIST] Kelvin current sense resistor
- From: "Joel Brown" <joel@xxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Thu, 25 Feb 2010 14:35:04 -0800
Sorry if this is not considered signal integrity related.
I am using a 0.001 (1 milli-ohm) resistor to sense up to 60A of current.
They make 4 terminal Kelvin resistors so that the voltage drop created by
the current flowing through the PCB to resistor connection do not cause an
error in the measurement.
I can also do a similar thing with a 2 terminal resistor by making two pads
on each side, one large one for the current and a small one for the sense.
However when I calculate the resistance of the solder connection, using a
resistivity of 1.21 E-7 ohm.m, a pad size of 2.54 x 5.46 mm and a joint
thickness of 10 mils,
I get a resistance of 2 micro-ohms, resulting in an error of 0.4% This would
say I don't really need a 4 terminal connection and I could even calibrate
out the error. Is there something I am missing?
Joel Brown
Chief Electrical Design Engineer
Z Microsystems, Inc.
9820 Summers Ridge Rd.
San Diego, CA 92121
Tel: 858-831-7011
Fax: 858-831-7001
<mailto:joel@xxxxxxxxxx> joel@xxxxxxxxxx
http://www.zmicro.com
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