Hioki 3332 - Notes on Connection Methods

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2.3 Making the Connections
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2.3.3 Notes on Connection Methods
Power
Input resistance on the current side
Load
Input resistance on
the voltage side
2MΩ
2mΩ
Input resistance on
the voltage side
2MΩ
2mΩ
Input resistance on the current side
Fig.1 Voltage Measurement Terminal Connected on the Load Side
Power
Load
Input resistance on the current side
Input resistance on
the voltage side
2MΩ
2mΩ
Input resistance on
the voltage side
2MΩ
2mΩ
Input resistance on the current side
Fig.2 Current Measurement Terminal Connected on the Load Side
Load
PowerPower
Load
The power meter can be connected either using the method shown below in
Fig.1, with the voltage measurement terminal connected on the load side, or
as shown in Fig.2, with the current measurement terminal connected on the
load side.
As shown in Fig.1, when the voltage measurement terminal is connected on
the load side, the power measurement includes a loss due to the inclusion of
the voltage measurement input resistance.
On the other hand, as shown in Fig 2, when the current measurement
terminal is connected on the load side, the power measurement includes a
loss due to the inclusion of the current measurement input resistance.
The method of connection should be shown so as to minimize the loss;
which connection is better depends on the relative magnitude of the current
and voltage. For example, measuring 600 V, 20 A supply:
Fig.1 loss = (600 [V])
2
÷ 2[MΩ] = 0.18 [VA]
Fig.2 loss = (20 [A])
2
× 2[mΩ] = 0.8 [VA]
In this case, therefore, the connection shown in Fig.1 should be used.
Next consider the case of measuring 600 V, 1 A system:
Fig.1 loss = (600 [V])
2
÷ 2[MΩ] = 0.18 [VA]
Fig.2 loss = (1 [A])
2
×2[mΩ] = 0.002 [VA]
In this case, the connection shown in Fig 2 allows more accurate
measurement.