3.13.2.3
Input linear scaling
Each RTD/mA input can be scaled linearly by the construction of a linear output
function in respect to the input. The curve consists of two points, where the y-axis
(
Input minimum and Input maximum) defines the input range and the x-axis (Value
minimum and Value maximum) is the range of the scaled value of the input.
The input scaling can be bypassed by selecting
Value unit = "Ohm" when
Input mode = "Resistance" is used and by selecting Value unit = "Ampere"
when
Input mode = "0...20 mA" is used.
Example for linear scaling
Milliampere input is used as tap changer position information. The sensor
information is from 4 mA to 20 mA that is equivalent to the tap changer
position from -36 to 36, respectively.
Input maximum
Input minimum
Input mode
”0..20mA”
4 mA
20 mA
Value minimum
-36
AI_VAL#
Value maximum
36
Value unit
”Dimensionless”
X130-Input#
Figure 44: Milliampere input scaled to tap changer position information
3.13.2.4
Measurement chain supervision
Each input contains a 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,
minimum/maximum value is shown in the corresponding output. The quality of the
corresponding output is set accordingly to indicate misbehavior in the RTD/mA
input.
Table 53: Function identification, limits for the RTD/mA inputs
Input
Limit value
RTD temperature, high
> 200 °C
RTD temperature, low
< -40 °C
mA current, high
> 23 mA
Resistance, high
> 2000 Ω
1MRS757644 H
Basic functions
620 series
Technical Manual
121
