CMF Non-Magnetic

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Vishay Dale

Revision: 23-Apr-14

3

Document Number: 31091

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

TEMPERATURE COEFFICIENT CODES

GLOBAL TC CODE

HISTORICAL TC CODE

TEMPERATURE COEFFICIENT

E

T-9

25 ppm/°C

H

T-2

50 ppm/°C

K

T-1

100 ppm/°C

L

T-0

150 ppm/°C

N

T-00

200 ppm/°C

LOAD LIFE SHIFT DUE TO POWER AND DERATING (AT +70 °C AND AT +125 °C)

The power rating for the CMF parts is tied to the derating temperature, the heat rise of the parts, and the

R for the load life performance.

When the tables/graphs below are used together they show that when the parts are run at their higher power ratings, the parts will run hotter,

which has the potential of causing the resistance of the parts to shift more over the life of the part.

LOAD LIFE SHIFT VS. POWER RATING

LOAD LIFE

MAXIMUM

R (TYPICAL TEST LOTS)

± 0.15 %

± 0.5 %

± 1.0 %

± 0.15 %

± 0.5 %

± 1.0 %

MODEL

POWER RATING AT +70 °C

POWER RATING AT +125 °C

CMF50..143

1/20 W and 1/10 W

1/8 W

1/4 W

1/20 W

1/10 W

1/8 W

CMF55..143, CMF07..143

1/10 W and 1/8 W

1/4 W

1/2 W

1/10 W

1/8 W

1/4 W

CMF60..143, CMF20..143

1/8 W and 1/4 W

1/2 W

3/4 W and 1 W

1/8 W

1/4 W

1/2 W

CMF65..143

1/4 W and 1/2 W

3/4 W

1 W and 1-1/2 W

1/4 W

1/2 W

3/4 W and 1 W

CMF70..143

1/4 W and 1/2 W

3/4 W

1 W and 1-3/4 W

1/4 W

1/2 W

3/4 W and 1-1/4 W

CMF resistors have an operating temperature range of -55 °C to +175 °C.



They must be derated at high ambient temperatures according to the derating curve.

Example:



When a CMF55..143 part is run at 1/8 W in a 70 °C ambient environment, the resistor will generate enough heat that the surface temperature

of the part will reach about 19 °C over the ambient temperature, and over the life of the part this could cause the resistance value to shift up

to ± 0.15 %.



If the same resistor was instead run at 1/4 W in a 70 °C environment, the element will heat up to about 30 °C over ambient, and over the life

of the part the resistance value could shift roughly ± 0.5 %.



And if the resistor was run at it maximum power rating of 1/2 W in a 70 °C environment, it will heat up to about 58 °C over ambient, and you

could see the resistance value shift roughly ± 1 % over the life of the part.

MATERIAL SPECIFICATIONS

Element

Vacuum-deposited nickel-chrome alloy

Coating

Flame retardant epoxy, formulated for superior

moisture protection

Core

Fire-cleaned high purity ceramic

Solderability

Continuous satisfactory coverage when tested

in accordance with MIL-R-10509

AMBIENT TEMPERATURE IN °C

125

DERATING

120

100

80

60

40

20

0

- 55 - 50

- 25

0

25

70

75

100

150

175

50

200

165

APPLIED POWER IN W

THERMAL RESISTANCE

120

100

80

60

40

20

0

0

0.125

0.25

0.375

0.5

0.75

0.875

1

1.125

0.625

CMF50..143

CMF55..143,

CMF07..

143

CMF60..143,

CMF20..143

CMF65..143,

CMF70..143