2-13
IM WT1801-01EN
External Current Sensor Conversion Ratio (
SENSOR RATIO;
option)
Set the conversion ratio used to measure the signal received by the external current sensor input connector (EXT)
from a current sensor that produces voltage. Set how many millivolts the current sensor transmits when 1 A of
current is applied (conversion ratio). Then, the input signal can be made to correspond to the numeric data or
waveform display data that is obtained when the current is directly applied to the input terminals. When using a
current sensor that produces current, set the conversion ratio as the CT ratio.
Measurement Function
Conversion
Ratio
Data before
Transformation
Transformation
Result
Current I
E
I
S
(current sensor output)
I
S
/E
Active power P
E
P
S
P
S
/E
Apparent power S
E
S
S
S
S
/E
Reactive power Q
E
Q
S
Q
S
/E
Max./min. current Ipk
E
Ipk
S
(current sensor output) Ipk
S
/E
Element1 to Element6
Use the soft keys to select an element, and then set the element’s external current sensor conversion ratio to a
value within the following range.
0.0001 to 99999.9999
Copying the External Current Sensor Conversion Ratio (Exec Copy Σ)
Copy the external current sensor conversion ratio of the selected input element to the other input elements in the
same wiring unit.
External Current Sensor Range and Conversion Ratio Configuration Example
When you measure a current with a maximum value of 100 A using a current sensor that produces 10 mV
when 1 A of current is flowing, the maximum voltage that the current sensor produces is 10 mV/A × 100 A = 1 V.
Therefore, configure the settings as indicated below.
• External current sensor range: 1 V
• External current sensor conversion ratio: 10 mV/A
• When you want to divide the external current sensor output by the conversion ratio and read the current of
the circuit under measurement directly, turn the external VT/CT scaling feature off. If the feature is turned
on, the value will be further multiplied by the CT ratio.
• When you are measuring a signal other than a sine wave (such as a distorted wave), you can obtain
accurate measurements by selecting the smallest measurement range that does not produce any of the
conditions below.
• The input peak over-range indicator at the top center of the screen illuminates or blinks in red.
• The measured values of the voltage and current are indicated as being overload values (“-OL-”).
2 Fundamental Measurement Conditions
