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4. SETTING AND PROCEDURE BEFORE OPERATION
4.4
Error Compensation by the Offset Value/Gain Value Setting
The AJ65BT-68TD error compensation is a function that compensates values at arbitrary 2 points
(offset value/gain value) within the usage temperature range at system startup or when a correct
temperature cannot be detected.
The error compensation is executed by reading the detected temperature value in the remote register
using a sequence program and monitoring the values using a peripheral device.
SW
MODE
0
NORMAL
1-8
TEST CH.
9
TEST
The following shows the characteristic of detected temperature value with respect to the input
temperature.
Compensate the detected
temperature value to equal
the input temperature.
* The error compensation may be executed using a standard DC voltage generator instead of inputting
the temperature directly to a thermocouple.
Power value of a standard
DC voltage generator
POINT
• The offset value/gain value can be obtained with a high accuracy when error compensation is
carried out at the minimum and maximum temperatures in the range used.
• Set the offset value/gain value while reading the detected temperatures values.
• Always set the offset and gain values within the allowable temperature input range so that the
gain value minus offset value is smaller than or equal to 10°C.
If an invalid error compensation (out of allowable temperature input range, gain value minus
offset value is greater than 10°C) is performed, the RUN LED flickers at a high speed (at 0.1
second intervals) and the offset value/gain value will not be set even if the offset value/gain
value setting switch is set at SET.
• The offset value and gain value are stored inside AJ65BT-68TD and are not erased even at
power off.
B RATE
STATION NO.
X10
X1
0 1
0 1
0 1
•
•
9
PW
•
2
•
2
8
2
•
3
•
3
7
3
RUN
•
4
6
4
6
4
•
5
5
L RUN
SD
MODE OFFSET
UP
RESET
RD
SET
0 1
9
L ERR.
8
2
7
3
6
4
5
GAIN
DOWN
-50 [°C]
OFFSET
=
OFFSET
Lower value of the two
points to be compensated
UP/DOWN adjustment of OFFSET/GAIN
80 [°C]
79.7
Characteristics before
error compensation
Characteristics after
error compensation
0
Input temperature
-49.7
-50 [°C]
Thermal electromotive force of a thermocouple with respect
to the input temperature to be the offset value/gain value.
4-5
MELSEC-A
GAIN
Higher value of the two
<
points to be compensated
GAIN
Compensate the detected
temperature value to equal
the input temperature.
80 [°C]
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