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FP-RTD-124 and cFP-RTD-124

8

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Unfortunately, not all TCR values are as well defined by standards 
organizations, and the behavior of RTDs with the same TCR value 
may vary from vendor to vendor. The variations are usually small, 
and the built-in linearization algorithms of the [c]FP-RTD-124 are 
appropriate for nearly all applications.

The [c]FP-RTD-124 uses a linearization curve known as the 
Callendar-Van Dusen equation to measure the temperature of 
RTDs. The equation is as follows:

Temperatures below 0

 °

C:

R

T

 = 

R

0

[1 

+

 A

 

× 

T

 

+

 B

 

× 

T

2

 

+

 C 

× 

T

3

 

× 

(

T

 – 100

°

C)]

Temperatures above 0 

°

C:

R

T

 = 

R

0

[1 

+

 A

 

× 

T

 

+

 B

 

× 

T

2

]

T

 = temperature in 

°

C

R

T

 = RTD resistance at temperature 

T

R

0

 = RTD nominal resistance at 0 

°

C

A, B, and C are coefficients given in Table 2.

Table 2 lists the coefficients used in this equation for each of the 
TCR values that the [c]FP-RTD-124 supports. If you have a 
nonstandard RTD that does not match one of these linearization 
curves, measure the resistance with the [c]FP-RTD-124 and 
convert the resistance to temperature in the manner suggested by 
the RTD vendor.

Table 2.  

Callendar-Van Dusen Coefficients Used by the [c]FP-RTD-124

TCR 

m

/

/

°

C

A

(

°

C)

–1

B

(

°

C)

–2

C

(

°

C)

– 4

3.750

3.81 

×

 10

–3

–6.02 

×

 10

–7

–6.0

 ×

 10

–12

3.851

3.9083 

×

 10

–3

–5.775 

×

 10

–7

–4.183 

×

 10

–12

3.911

3.9692 

×

 10

–3

–5.8495 

×

 10

–7

–4.233

 ×

 10

–12

3.916

3.9739

 ×

 10

–3

–5.870 

×

 10

–7

–4.4

 ×

 10

–12

3.920

3.9787

 ×

 10

–3

–5.8686 

×

 10

–7

–4.167 

×

 10

–12

3.928

3.9888

 ×

 10

–3

–5.915 

×

 10

–7

–3.85 

×

 10

–12

Содержание Fieldpoint cFP-RTD-124

Страница 1: ...how to install and use the National Instruments FP RTD 124 and cFP RTD 124 three wire RTD and resistance input modules referred to inclusively as the c FP RTD 124 For details on configuring and access...

Страница 2: ...any module or position 1 used for the FP RTD 124 module 2 Align the FP RTD 124 alignment slots with the guide rails on the terminal base 3 Press firmly to seat the FP RTD 124 on the terminal base When...

Страница 3: ...cFP RTD 124 prevent backward insertion 2 Press firmly to seat the cFP RTD 124 on the backplane 3 Using a number 2 Phillips screwdriver with a shank of at least 64 mm 2 5 in length tighten the captive...

Страница 4: ...es at the signal end Taking RTD Measurements with the c FP RTD 124 The c FP RTD 124 has eight input channels All eight channels share a common ground that is isolated from other modules in the FieldPo...

Страница 5: ...terminals COM and SENSE Figure 4 Four Wire RTD Connections on One Channel Taking Measurements from Three Wire RTDs NI recommends the c FP RTD 122 for three wire RTD measurements because it includes sp...

Страница 6: ...m Two Wire RTDs Connect one wire of a two wire RTD to the SENSE terminal and the other wire to the SENSE terminal Use a short jumper wire to connect the SENSE terminal to the EXCITE terminal Use anoth...

Страница 7: ...c FP RTD 124 linearizes resistance values and returns readings in units of temperature The available ranges are 73 to 1 123 K 200 to 850 C and 328 to 1 562 F You can configure each channel independen...

Страница 8: ...perature in C RT RTD resistance at temperature T R0 RTD nominal resistance at 0 C A B and C are coefficients given in Table 2 Table 2 lists the coefficients used in this equation for each of the TCR v...

Страница 9: ...e The most accurate way to measure temperature from RTDs is the four wire method shown in Figures 2 and 3 With this method one pair the EXCITE and COM leads carries the current through the RTD The oth...

Страница 10: ...l on the cFP BP x backplane to the system safety ground The backplane PE ground terminal has the following symbol stamped beside it Connect the backplane PE ground terminal to the system safety ground...

Страница 11: ...3 to 1123 K 200 to 850 C 328 to 1562 F Resistance 0 to 400 Temperature accuracy Resolution 0 016 C Resistance accuracy Offset error 0 03 typical 0 1 max Gain error 0 06 typical 0 1 max Resolution 0 00...

Страница 12: ...dules are intended for indoor use only For outdoor use FieldPoint modules must be mounted inside a sealed enclosure Operating temperature 40 to 70 C Storage temperature 55 to 100 C Humidity 10 to 90 R...

Страница 13: ...romagnetic Compatibility CE C Tick and FCC Part 15 Class A Compliant Electromagnetic emissions EN 55011 Class A at 10 m FCC Part 15A above 1 GHz Electromagnetic immunity Evaluated to EN 61326 1997 A1...

Страница 14: ...operating instructions FieldPoint terminal base operating instructions If you no longer have the print versions of these documents you can find them online at ni com If you have searched the technica...

Страница 15: ...ly 02 413091 Japan 03 5472 2970 Korea 02 3451 3400 Malaysia 603 9596711 Mexico 001 800 010 0793 Netherlands 0348 433466 New Zealand 09 914 0488 Norway 32 27 73 00 Poland 22 3390 150 Portugal 210 311 2...

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