ABB RELION REX640 Technical Manual page 173

1MRS759142 F
Self-supervision
Each input contains functionality to monitor the input measurement chain. The
circuitry monitors the RTD channels continuously and reports a circuitry break of
any enabled input channel. If the measured input value is outside the limits, the
minimum/maximum value is shown in the corresponding output. The quality of the
corresponding output is set accordingly, and the fault is reported at SENSOR_FLT to
indicate misbehavior in the mA/RTD input.
Table 103: Limits for the mA/RTD inputs
mA/RTD input
RTD temperature, high
RTD temperature, low
mA current, high
mA current, low
Resistance, high
Resistance, low
When necessary, the valid measuring range may be narrower than the default of the
selected measuring range. A narrower range can be defined with the
and
RTD input supervision
RTD sensor currents are measured continuously at a fixed rate. The delay between
the RTD current/connectivity checks is about 10s at a maximum (if all 10 RTD
channels are active). If the RTD current is not within ±5% of the expected current,
the measurement is considered to be invalid, and the channel is discarded until a
valid current is obtained.
The expected currents are 1 mA for RTD sensors and 0.21 mA for pure resistance.
While the quality of the invalid input is set accordingly, a warning is also provided on
the Relay Status page of LHMI/WHMI. The invalid signal is deactivated as soon as
the corresponding input signal is within the valid range.
mA input supervision
The current limit for mA input supervision is defined by parameter
level . Value must be below Input minimum parameter. SENSOR_FLT is activated,
and measurement quality is set bad when measured current is below set limit. The
supervision is disabled if
3.15.3.2 Output mode
A measurement value from another function, mA input or RTD input can be
represented by the mA output. The mA output scaling principle is otherwise similar
1
Low limit is not defined for the resistance input. In practice the low limit is 0 because the
resistance cannot be negative.
REX640
Technical Manual
Value maximum settings.
Delay for SENSOR_FLT activation depends on the connected sensor type,
amount of connected channels and RTD module type. The maximum
delay is 10 seconds.
Sensor fault level is set to 0 mA.
Limit value
> 200°C
< –40°C
> 24 mA
< –24 mA
> 4000 Ω
1
Not defined
Basic functions
Value minimum
Sensor fault
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