4-14
IM 760301-01E
Explanation
The output of current sensors that output voltage, such as shunts and clamps, can be
input to the current sensor input connector of an element and measured. When using a
current sensor that outputs current, set the transformation ratio as a CT ratio (see
section 4.5).
• Display Position of the Target Element and Specified Range
It is the same as section 4.3, “Setting the Measurement Range during Direct Input.”
• Selecting the External Current Sensor Input Connector
To measure the current using the input signal from the external current sensor input
connector, EXT SENSOR must be selected (EXT SENSOR key illuminated) by
pressing EXT SENSOR, and then the external current sensor range must be
specified.
• Selecting the External Current Sensor Range
Two types of range settings are available: fixed and auto.
• Fixed Range
• When the crest factor is set to 3
Select 50 mV, 100 mV, 200 mV, 500 mV, 1 V, 2 V, 5 V, or 10 V.
• When the crest factor is set to 6
Select 25 mV, 50 mV, 100 mV, 250 mV, 500 mV, 1 V, 2.5 V, or 5 V.
• Auto Range
When AUTO is pressed, the AUTO key illuminates and auto range is enabled. The
range changes automatically depending on the amplitude of the input signal. The
switching conditions and precautions are the same as the descriptions given in
section 4.3, “Setting the Measurement Range during Direct Input.” The different
ranges used in the auto mode are the same as those available for fixed range.
• Setting the External Current Sensor Transformation Ratio
The transformation ratio can be set in the range of 0.0001 to 99999.9999.
• Configuration Example of the External Current Sensor Range and
Transformation Ratio
When measuring a current with a maximum value of 100 A using a current sensor that
outputs 10 mV when 1 A of current is flowing, the maximum voltage that the current
sensor outputs is 10 mV/A
×
100 A = 1 V. Therefore, set 1 V for the external current
sensor range and 10 mV/A for the external current sensor transformation ratio.
Note
•
When attempting to directly read the current of the circuit under measurement by multiplying
the output of the external current sensor by the transformation ratio, turn OFF the external
VT/CT scaling function (see section 4.5). If it is turned ON, the value will be multiplied by the
CT ratio.
•
When measuring a signal other than a sine wave such as a distorted wave, accurate
measurements can be obtained by selecting the minimum measurement range that does not
meet the conditions below.
•
The input peak over-range indicator at the top center of the screen illuminates or blinks.
•
The measured values of the voltage and current indicate over range [-OL-].
•
For the list of the ranges and transformation ratios of all input elements, see section 3.17,
“Displaying the Setup Parameter List.” You can change the measurement range and the
external current sensor transformation ratio with the list displayed. However, for input
elements whose current measurement range is not set to external current sensor input range,
the change in the transformation ratio is not applied to the list display.
4.4 Setting the Measurement Range When Using the External Current Sensor