<3. Parameter Setting>
3-17
IM 01C50T03-02EN
(4) Execute the parameter of the Sensor Backup
return instruction.
Setting
parameter
Setting
value
Remarks
G21:RETURN
S1
EXEC
After execution, the
system returns to the NO
EXEC state automatically.
(2) Checking the sensor backup state
To check the backup state, read the following
parameter.
Parameter
Value
Remarks
G20:BACKUP
ST
N/A
Sensor Backup function is
disabled.
(Sensor1 and Sensor2
are used to measure the
different targets.)
SENSOR1 The temperature transmitter
outputs an input of Sensor1.
SENSOR2 The temperature transmitter
outputs an input of Sensor2.
(3) Returning from the backup status (Release
of “AL.23 Backup S1 Fail” alarm)
Even if Sensor1 is recovered to the normal
operation state during backup operation (an
“AL.23 Backup S1 Fail” alarm has occurred), the
temperature transmitter outputs an input of Sensor2
until the backup operation is reset by the parameter
or by switching the power OFF.
To return the output back to the Sensor1 input,
execute the parameter of the Sensor Backup return
instruction.
Setting
parameter
Setting
value
Remarks
G21:RETURN
S1
EXEC
After execution, the
system returns to
the NO EXEC state
automatically.
(4) Releasing the “AL.24 Backup S2 Fail” alarm
When the Sensor Backup function is enabled and
if Sensor2 has failed, the temperature transmitter
outputs an input of Sensor1 as it is, however, an
“AL.24 Backup S2 Fail” alarm occurs. To release
this failure, follow the procedure below.
(1) Recover Sensor2 (by repairing wiring, replacing
the sensor, and other measures).
(2) Execute the parameter of the Sensor Backup
return instruction.
Setting
parameter
Setting
value
Remarks
G21:RETURN
S1
EXEC
After execution, the
system returns to
the NO EXEC state
automatically.
3.2.15 Sensor Matching Function
This function is only available when optional
specification/CM1 is specified.
The sensor matching function sets specific
sensor constants in the temperature transmitter to
significantly improve the temperature measurement
accuracy.
(1) Sensor matching function of YTA710
The properties of the RTD sensor for the YTA 710
comply with the standard specified in IEC 60751.
As the characteristics of the RTD sensor, there
are variations within the range permitted by the
standard, and they may cause measurement
errors. The Sensor Matching function improves
the precision of temperature measuring by
programming the Callendar-Van Dusen constants,
specific numbers defined for each RTD sensor, in
the temperature transmitter.
The following relationship exists between
the resistance (Rt) of a RTD sensor and the
temperature (t) at that time.
R
t
= R
0
{
1 + α (1 + 0.01δ) t - t
2
- (t - 100) t
3
}
αδ
10
4
αβ
10
8
i
where, R
t
=Resistance (ohms) at temperature
t
(°C)
R
0
=Sensor-specific constant (Resistance at 0°C)
α (alpha)=Sensor-specific constant
δ (delta)=Sensor-specific constant
β=Sensor-specific constant (0 if t>0°C)
The exact values for R0, α, δ and β are
specific to each RTD sensor, and are obtained
by testing each individual sensor at various
temperatures.
Generally, constants A, B and C are also used as
the characteristic coefficients of the RTD instead of
α, δ and β. The relationship is described as follows.
R
t
= R
0
{1 + At + Bt
2
+ C ( t - 100 ) t
3
}
ii
where, R
t
=Resistance (ohms) at temperature
t
(°C)
R
0
=Sensor-specific constant (Resistance at 0°C)
A=Sensor-specific constant
B=Sensor-specific constant
C=Sensor-specific constant (0 if t>0°C)
These two equations are equivalent. Model YTA710
can cope with either case (α, δ and β, or A, B and
C) as above mentioned.
