Specifications

2645A Specifications A

2645A Thermocouple per ITS-1990 Measurement Specifications A-27.

Tables A-35 to A-36 provide 2645A specifications for the thermocouple measurement function per ITS-1990.

Table A-35. 2645A Thermocouple General Specifications

Specification

Input Impedance

Open Thermocouple Detect

Temperature Coefficient

Accuracy at -20°C

Characteristic

100 MΩ minimum in parallel with 150 pF

Operates by injecting a small ac signal into the input after each measurement. A thermocouple resistance greater than 1 kΩ to 10 kΩ is detected as an open input.

To calculate Thermocouple accuracy for temperatures between 28ºC and 60ºC, or -10ºC and 18ºC, use a linear interpolation between the two applicable points. e.g., if the applicable spec at 28ºC is .6 and the spec at 60ºC is 1.1, then the spec at 40ºC is (1.1-.6)*(40-28)/(60- 28)+.6 = .5*(12.32) + .6 = .7875.

Multiply the -10°C to + 60°C accuracy specification by 2. After 1 hour warm-up. For accuracy between -10°C and -20°C, interpolate linearly.

Table A-36. 2645A Thermocouple Specifications

Thermocouple

Resolution

 

 

Accuracy ± ºC

 

 

 

 

 

18ºC to 28ºC

-10ºC to 60ºC

 

 

 

 

90

 

1 Year

1 Year

Day

 

 

 

 

 

 

 

Type

J

K

N

Temperature ºC

-100 to 80 80 to 230 230 to 760

-100 to -25 -25 to 120 120 to 1000 1000 to 1372

-100 to -25 -25 to 120 120 to 1000 1000 to 1300

.3

.2

.2

.4

.3

.3

.3

.5

.5

.4

.3

Slow

0.8

0.7

0.7

1.0

0.8

0.9

1.2

1.4

1.1

1.0

1.0

Slow

0.9

0.8

0.8

1.1

0.9

1.1

1.5

1.5

1.3

1.1

1.2

Fast

1.6

1.4

1.3

2.0

1.7

1.8

2.3

2.8

2.3

2.0

1.9

Slow

0.9

0.9

1.0

1.2

1.0

1.5

2.0

1.5

1.3

1.2

1.6

Fast

1.7

1.5

1.5

2.1

1.8

2.2

2.9

2.9

2.4

2.1

2.4

A-23

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Fluke 2640A, 2645A user manual Table A-35 a Thermocouple General Specifications, Slow Fast

2645A, 2640A specifications

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