# Appendix b. the sensor matching function, B.1 specifications – Yokogawa Wireless Temperature Transmitter YTA510 User Manual

## Page 36

IM 01C50T03-01E

B-1

APPENDIX B. THE SENSOR MATCHING FUNCTION

APPENDIX B. THE SENSOR MATCHING

FUNCTION

B.1 Specifications

Function: The sensor-specific constants can be pro-
grammed into the transmitter.

Applicable model: YTA310 /CM1, YTA320 /CM1

RTD sensor: Pt100, Pt200, Pt500

Significant temperature measurement accuracy im-
provement can be attained using a temperature sensor
that is matched to a temperature transmitter. This
matching process entails teaching the temperature
transmitter the relationship between resistance and
temperature for a specific RTD sensor. This relation-
ship, approximated by the Callendar-Van Dusen
equation, is described as:

Rt = R0 {1 +

␣ ( 1 + 0.01␦ ) t - ␣␦ / 10

4

t

2

-

␣␤ / 10

8

( t - 100 ) t

3

}

where: Rt = Resistance (ohms) at Temperature t (

ЊC)

R0 = Sensor - Specific Constant
(Resistance at t = 0

ЊC)

␣ = Sensor - Specific Constant
␦ = Sensor - Specific Constant
␤ = Sensor - Specific Constant (0 at t > 0 ЊC)

The exact values for R0 ,

␣, ␦, and ␤ are specific to

each RTD sensor, and are obtained by testing each
individual sensor at various temperatures. These
constants are known as Callendar-Van Dusen con-
stants.

Generally the constants R0, A, B, and C are also being
used as the characteristic coefficients of the sensor

␣, ␦, and ␤. These are derived from the

IEC Standard Curve and the relationship is described
as:

Rt = R0 [ 1 + At + Bt

2

+ C ( t - 100 ) t

3

]

where: Rt = Resistance (ohms) at Temperature t (

ЊC)

R0 = Sensor - Specific Constant
(Resistance at t = 0

ЊC)

A = Sensor - Specific Constant

B = Sensor - Specific Constant

C = Sensor - Specific Constant (0 at t > 0

ЊC)

These two equations are equivalent. A model YTA can
cope with either case above-mentioned.

IMPORTANT

There is the following limitations for R0,

,

,

,

A, B, and C with the YTA.

IT is necessary to enter the value, which is
normalized by the exponential part specified
for each parameter. See Table B.1.

It is necessary to enter the value, which is
rounded off to three or two decimal places
specified for each parameter. See Table B.1.

When a three decimal place data is entered,
it may be automatically changed to the four
decimal place data that is equivalent to the
input data.

Example: +3.809 E-3

+3.8089 E-3

Table B.1

T0B01.EPS

Item

Number of

decimal

places

exponential

part

Input

Example

Factory

Initial

R0

A

B

C

2

3

3

3

3

3

3

non

E-3 (10

-3

)

E-7 (10

-7

)

E-12 (10

-12

)

E-3 (10

-3

)

E0 (10

0

)

E-1 (10

-1

)

+ 100.05

+ 3.908 E-3

- 5.802

E-7

- 0

E-12

+ 3.850 E-3

+ 1.507 E0

+ 0

E-1

+100

+3.9083 E-3

-5.7749 E-7

-4.183 E-12

+3.8505 E-3

+1.4998 E0

+1.0862 E-1