Yokogawa Wireless Temperature Transmitter YTA510 - Manual (Page 73)

A2-4
IM 01C50T02-01E
Access the parameter CAL_STATE_1 and set 2.
0 = User Cal Off (Invalidate user-set calibration
values)
1 = User Cal On (Validate user-set calibration
values)
2 = Calibration Exec (User calibration mode)

Check that the sensor type and number of connection
wires are set correctly for the sensor 1 input.
Refer to Table 5.16 in Section 5.6.4, “Parameters of
Transducer Block,” and apply the low level voltage or
resistance appropriate for the sensor type, to the input
terminals for the sensor 1 input.

Access the parameter CAL_POINT_LO_1, and write
the voltage or resistance value that is currently applied.

Vary the input voltage or resistance to a high level
appropriate for the sensor type.

Access the parameter CAL_POINT_HI_1, and write the
voltage or resistance value that is currently applied.

Access the parameter CAL_STATE_1 and return the
setting to 1 (validate the user-set calibration values).
IMPORTANT
While adjusting one input, connect the correct
sensor to the other input. If you do not connect a
sensor to the other input, set ‘No Connection’ to
the sensor type.
(5) Setting Up the Sensor Matching Function
The sensor matching function is applicable to
Pt100, Pt200, and Pt500 sensors only. The
YTA320 employs the temperature-to-resistance
characteristics of RTDs stipulated by IEC
Publication 751-1995, which permits ranges
of variations for each sensor type, causing
measurement errors. The sensor matching function
allows you to program each sensor’s inherent
constants called Callendar-Van Dusen constants, in
the transmitter, and reduces those errors to improve
the temperature measurement accuracy.
The resistance value of an RTD and the
temperature t have the following relation:
Rt = R0 {1 + α(1 + 0.01δ)t – α • δ/10 4 t 2
– a • β/10 8 (t – 100)t 3 } (Eq. 1)
where
Rt = resistance (Ω) at temperature t (°C)
R0 = inherent constant of the sensor
=resistance (Ω) at 0°C
α = inherent constant of the sensor
δ = inherent constant of the sensor
β = inherent constant of the sensor
(= 0 if t > 0°C)
The precise values of R0, α, δ, and β can be
obtained by measuring the characteristics of each
RTD at several temperatures. This relation is also
expressed by a different equation using inherent
constants R0, A, B, and C as shown below.
Rt = R0 {1 + A• t + B • t 2 + C(t – 100)t 3 }
(Eq. 2)
where
Rt = resistance (Ω) at temperature t (°C)
R0 = inherent constant of the sensor
= resistance (Ω) at 0°C
A = inherent constant of the sensor
B = inherent constant of the sensor
C = inherent constant of the sensor
(= 0 if t > 0°C)
Equations 1 and 2 are equivalent to each other, and
the YTA320 can handle either equation and allows
you to specify either the values of α, δ, and β, or the
values of A, B, and C.
The following shows the procedure to set up the
sensor matching function for sensor 1 by entering
the values of α, δ, and β for example. Also perform
the setup for sensor 2, if connected, in the same
way.