Document Number: 63086

For technical questions, contact: foil@vishay.com

www.vishay.com

Revision: 02-Mar-05

2

Power Current Sense Resistors

Rapid

ΔR Stabilization - Low WCR - Low TCR

Vishay Foil Resistors

SALES

• AMERICAS: foilsales.usa@vishay.com

• ASIA/JAPAN: foilsales.asia@vishay.com

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• GERMANY/CZECH REPUBLIC/AUSTRIA: foilsales.eucentral@vishay.com

• FRANCE/SWITZERLAND/SOUTHERN EUROPE: foilsales.eusouth@vishay.com

• ISRAEL: foilsales.israel@vishay.com

Kelvin, 4-terminal, connections are utilized for these low

ohmic value products to measure a precise voltage drop

across the resistive element. In these applications the

contact resistance, lead resistance, and their TCR effect may

be greater than that of the element itself and could cause

significant errors if the standard 2-terminal connection is

used. Figure 5 shows a high impedance measurement

negates their lead resistance and TCR effect. With the

negated and only the resistance and TCR of the element R

are sensed. This method of measurement is essential for

precise current sensing.

FIGURE 1 - RAPID STABILIZATION

FIGURE 3 - TEMPERATURE COEFFICIENT

RESISTANCE

FIGURE 5 - KELVIN CONNECTION

15

10

5

0

- 5

- 10

- 15

0

20

40

60

80

100

120

140

160 180

200

TIME IN SECONDS

RESISTANCE CHANGE UNDER LOAD AT 10 WATTS

MOUNTED ON COOLED HEAT SINK HELD AT + 25 °C

AMBIENT TEMPERATURE (

NO LOAD APPLIED

+ 8ppm/°C

+ 8ppm/°C

+ 200

- 200

5

2

1

+

5

2

+

5

5

-

- 250

- 200

- 150

- 100

- 50

0

50

100

150

200

250

+ 2

ppm

/

- 2

ppm

+ 2

ppm

- 2

pp

m/

0

R

FIGURE 2 - POWER COEFFICIENT (WCR)

FIGURE 4 - POWER DERATING CURVE

60

40

20

0

- 20

- 40

- 60

0

1

258

10

APPLIED POWER IN WATTS

RESISTANCE CHANGE VS APPLIED POWER

MOUNTED ON COOLED HEAT SINK HELD AT + 25 °C

+ 100

+ 75

+ 50

+ 25

0

- 50

0

+ 50

+ 100

+ 150

+ 200

AMBIENT TEMPERATURE

- 55 °C

+ 25 °C