IM 253401-01E
4-9
4
Setting Measurement Conditions
Explanation
Scaling Function in combination with External Sensor Input
This function is useful for measuring current, power and such when you are using an external
sensor, and have connected their output to the input elements. You set the scaling value to the
current or power value, computed from the sensor. When the scaling function is turned ON,
measured values which have been converted to the corresponding values for the transformer
primary sides, can been displayed or otherwise output. This function is exactly the same as the
one described previously for use with PT/CT.
Measured/computed value
Scaled result
Current A
E
×
A
E: External sensor scaling value
Active power W
E
×
W
Reactive power var
E
×
var
Apparent power VA
E
×
VA
Selecting the Setting Format of the Scaling Value
The following two setting formats are available. The initial value is “ALL”. At the WT110, this
selection menu will not appear.
• ALL : Select this when the same scaling values should be applied to all elements together.
• EACH : Select this when the scaling values should only be applied to each element seperately.
Setting the Scaling Value
The procedure to set the scaling values depends on the setting format (previous setting). The
setting ranges from 0.001 to 1000. The initial value is 50.00. In case of the WT110, the scaling
value is set at display C.
• When ALL is selected:
The scaling value set at display C will be applied to all elements together.
• When EACH is selected:
• The scaling value set at display A will be applied to element 1 only.
• The scaling value set at display B will be applied to element 2 only. This selection will not
appear on model 253502.
• The scaling value set at display C will be applied to element 3 only.
After having selected ALL or EACH and entered the scaling values, press the ENTER key to
end this scaling setting.
Selecting the Measurement Range (Current, with Scaling function ON)
After having set the scaling values, select the menu for the current measurement range. Select
the rated output of the external sensor from this menu (refer to the Operating Procedure on the
previous page). Scaling of the external sensor input will start as soon as you press the ENTER
key after selecting. Scaling will stop as soon as you select a measurement range other than
external sensor input from the menu.
Setting Example of Scaling Values for External Sensor Input
• In case the rated specs of the external sensor are 50A/50mV, measurement range is 50mV, then
50A/50mV
×
50mV = 50A: scaling value is 50.00
• In case the rated specs of the external sensor are 100A/50mV, measurement range is 50mV, then
100A/50mV
×
50mV = 100A: scaling value is 100.00
• In case the rated specs of the external sensor are 50A/80mV, measurement range is 50mV, then
50A/80mV
×
50mV = 31.25A: scaling value is 31.25
However, since the setting range is 50mV, use a setting within the 0 to 50mV range.
Note
• When performing measurements using the external sensor, make sure to turn off the scaling function for
the external PT/CT. When this function is ON, the scaling value of the CT ratio will interfere.
• The input range for the external sensor can only be of the manual type.
• When you switch from external sensor input to direct, auto range input, an error will appear. First, select
manual range for direct input and afterwards select auto range. (same goes for setting by communication
interface.)
4.5 Selecting the Measurement Range and Setting the Scaling Value when External Sensor is Used (option)
