YOKOGAWA WT200 User Manual page 34

IM 253421-01E
3.8 Wiring the Measurement Circuit when Using the External Sensor
Note
• The external sensor must be selected carefully, because the frequency and phase
characteristics of the sensor affects the measured value.
• Make the lead wires between the external sensor and the instrument as short as possible to
minimize measurement errors caused by stray capacitance and resistance of the lead wires.
• When using a shunt-type current sensor, note the following points when connecting the
external sensor cable to minimize errors:
• Connect the shield wire of the external sensor cable to the L side of the shunt output
terminal (OUT).
• Make the area that the lead wires create between the sensor and the external sensor
cable as small as possible. This reduces the effects caused by field lines (caused by
measurement current) entering this area and the external noise.
Shunt-type current sensor
OUT H
I
±
OUT L
• As shown in the figure below, connect the shunt-type current sensor to the power grounding
side. If you have to connect the sensor to the non-earth side, use a wire that is thicker than
AWG18 (conductive cross-sectional area of approx. 1 mm
instrument to reduce the effects of common mode voltage. Take safety and error reduction in
consideration when constructing an external sensor cable.
External shunt
• If the measurement circuit is not grounded and the measured signal is of high frequency or
high power, the effects of inductance of the shunt-type current sensor cable become large. In
this case, use an isolation sensor (CT, DC-CT, or clamp).
Clamp sensor
• Make sure you have the polarities correct when making the connections. Otherwise, the
polarity of the measurement current will be reversed and correct measurements cannot be
made. Be especially careful when connecting the clamp type current sensor, because it is
easy to reverse the polarity.
• You can use the scaling function to directly read the measured values on the display. For the
procedure, see section 4.6, "Selecting the Measurement Range and Setting the Scaling
Constant when External Sensor is Used (option)."
The area created by the lead wires
Input terminal of the WT200
External sensor cable
Shield wires
2
) between the sensor and the
V
Voltage input terminal
±
A
Current input terminal
±
Ext. sensor input terminal
V
Voltage input terminal
±
A
Current input terminal
±
Ext. sensor input terminal
LOAD
LOAD
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