Surface mounted four terminal resistor

Abstract

An electrical resistor has a surface mounted four terminal current sensor of a very low resistance value and capable of handling short pulses of high power. It comprises a flat metal late, 1 to 50 mils thick, of an alloy of high electrical resistivity, to which are welded, on two opposite sides, two flat metal plates of very high electrical conductivity which serve as terminations for electrical interconnection. A slot is cut, from the outside edge toward the center, into each of the two termination plates which divides them into a wide pad for connection of current carrying wires and a narrow one for voltage sensing. The depth of the slots is optimized to get the best stability of resistance readings with changing ambient temperature and under influence of the self-heating effect.

1. A surface mounted four terminal connection current sensing resistor for Kelvin type measurement comprising, ;
 a flat metal plate made of a resistive alloy having opposite side surface portions,  
 a pair of high conductivity  conductive metal terminal plates each secured  welded to a separate side of the resistance plate with a high thermal conductive dielectric cement  and supported by the resistive plate,  
 a slot inserted  cut transversely in the terminal plates creating four separate pad portions,  
 said slot set to a partial depth that determines the best  stability of resistance for  sensed voltage drop over the resistor,  
 said pad portions  terminal plate being split into a current pad and a sense pad with each pad portion comprising terminal connection areas;  
 said current pad portion having a length greater in a direction from said slot than the corresponding length of said sense pad portion,  
 said sense pad portions being  enabling a measurement of voltage drop proportional to the value of current flowing between the said current pads and resistive to drifts in electrical measurements created by temperature rises that occur due to pluses of high power or high  to changing ambient temperatures.  
 
     
     
       2. A surface mount four terminal resistor having a stability of resistance, comprising:
   a flat metal resistive plate made of a resistive alloy material having opposite first and second sides;        a first plate of conductive metal attached to and supported by the first side of the flat metal resistive plate;        a second plate of conductive metal attached to the second side of the flat metal resistive plate;        a first slot cut transversely in the first plate;        a second slot cut transversely in the second plate;        the stability of measured resistance at least partially determined by the depth of each slot;        the first slot dividing the first plate of conductive metal into a first sense pad and a first current pad;        the second slot dividing the second plate of conductive metal into a second sense pad and a second current pad;        each of the pads providing a terminal connection area;        each of the current pads having a length greater in a direction from said slot than the corresponding length of the corresponding sense pad.     
     
     
       3. The surface mount four terminal resistor of  claim 2  wherein the length of each of the current pads is at least twice as long as the corresponding length of the corresponding sense pad. 
     
     
       4. The surface mount four terminal resistor of  claim 2  wherein the resistor is bonded to a metal substrate with a dielectric cement for better heat dissipation.