ABB 615 Series ANSI, Technical Manual

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Section 3
1MAC050144-MB C
Basic functions
74 615 series ANSI
Technical Manual
Table 46: Function identification, limits for the RTD/mA inputs
3.10.7 Selfsupervision
Each input sample is validated before it is fed into the filter algorithm. The samples are
validated by measuring an internally set reference current immediately after the inputs are
sampled. Each RTD sensor type has expected current based on the sensor type. If the
measured offset current deviates from the reference current more than 20%, the sample is
discarded and the output is set to invalid. The invalid measure status deactivates as soon
as the measured input signal is within the measurement offset.
3.10.8 Calibration
RTD and mA inputs are calibrated at the factory. The calibration circuitry monitors the
RTD channels continuously and reports a circuitry break of any channel.
3.10.9 Limit value supervision
The limit value supervision function indicates whether the measured value of AI_INST#
exceeds or falls below the set limits. All the measuring channels have an individual limit
value supervision function. The measured value contains the corresponding range
information AI_RANGE# and has a value in the range of 0 to 4:
• 0: “normal”
• 1: “high”
• 2: “low”
• 3: “high-high”
• 4: “low-low”
The range information changes and the new values are reported.
Input Limit value
RTD temperature, high > 200 °C
RTD temperature, low < -40 °C
mA current, high > 23 mA
Resistance, high > 2000 Ω