YOKOGAWA WT500 User Manual page 111

Explanation
IM 760201-01E
4.5 Setting the Measurement Ranges for an External Current Sensor (Optional)
The output of current sensors that produce voltage, such as shunts and clamps, can be
applied to an element's current sensor input connector and measured. When using a
current sensor that produces current, set the conversion ratio as the CT ratio (see section
4.6 for instructions).
Display Positions of the Element Being Set and the Specified Range
The display positions are the same as those described in section 4.4, "Setting the
Measurement Range during Direct Input."
Selecting the External Current Sensor Input Connector
To measure the current of an element using the input signal from the external current
sensor input connector, you must select the Ext Sensor box of that element and then
specify the external current sensor range.
Selecting the External Current Sensor Range
There are two types of ranges, fixed and auto.
• Fixed Range
• When the crest factor is set to 3
You can 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
You can select 25 mV, 50 mV, 100 mV, 250 mV, 500 mV, 1 V, 2.5 V, or 5 V.
• Auto Range
When you press SHIFT+ (AUTO) or select Auto in the external current sensor
range entry box, the AUTO indicator lights and the auto range feature is enabled.
The range is switched automatically depending on the amplitude of the input signal.
For auto range switching conditions and precautions, see section 4.4, "Setting the
Measurement Range during Direct Input." The different ranges used in the auto range
are the same as those listed above for the fixed range.
Setting the External Current Sensor Conversion Ratio
The conversion ratio can be set to a value from 0.0001 to 99999.9999.
External Current Sensor Range and Conversion Ratio Configuration
Example
When measuring 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, set the external current sensor
range to 1 V and the external current sensor conversion ratio to 10 mV/A.
Note
• When attempting to directly read the current of the circuit under measurement by multiplying
the output of the external current sensor by the conversion ratio, turn off the external VT/CT
scaling feature (see section 4.6 for instructions). If it is turned on, the value will be further
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 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 lights or blinks in red.
• The measured values of the voltage and current are indicated as over range ("-OL-").
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App
Index
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