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4-84
Chapter 4. Functions
z
z
CT operation
When set to "0: Continuous current measurement," the current is measured
regardless of whether V-P block output is ON or OFF. When set to "1: Detection
of heater burnout for terminal OUT," different types of current value are measured
depending on whether V-P block output is ON or OFF.
The measurable current values and detectable errors based on the "CT operation"
settings are shown in the table below.
CT operation
Current value type
Current measurement
possible / not possible
Error detection setting
value
Error detection
Continuous current
measurement
Current when
output ON
Measurable
Heater burnout
detection current value
Current low limit error
(Current value < Set value)
Overcurrent detection
current value
Current high limit error
(Current value > Set value)
Current when
output OFF
Not measurable
(Current value = 0.0 A)
None
None
Time proportioning
current value
Not measurable
(Current value = 0.0 A)
None
None
Detection of
heater burnout for
terminal OUT
Current when
output ON
Measurable
Heater burnout
detection current value
Heater burnout
(Current value < Set value)
Overcurrent detection
current value
Overcurrent
(Current value > Set value)
Current when
output OFF
Measurable
Short-circuit detection
current value
Short-circuit
(Current value > Set value)
Time proportioning
current value
Measurable
None
None
Handling Precautions
•
The time proportioning current value can be calculated using the following
formula.
Time proportioning current value = Measured current when output ON × √
(Time proportional output ON time ÷ Time proportional cycle)
•
The time proportioning current value cannot be measured correctly if "Time
proportioning operation type" is set to "0: Priority on controllability." If using
the time proportioning current value, set "Time proportioning operation type"
to "1: Priority on device life." If the version of the MAIN block firmware is 5.x.x
or later (where x stands for any number), the time proportioning current value
= 0.0 A when set to "Priority on controllability."
•
The detection status for heater burnout, overcurrent, and short-circuit is
reflected in the value of the standard bit.
•
The current low limit error status for continuous current measurement is
reflected in the value of the standard bit for heater burnout detection, and the
current high limit error status is reflected in the standard bit for overcurrent
detection.
14 - 2 Standard Bit Codes and Standard Numerical Codes (p. 14-6)