Hioki PW3335 - 2.6 Activating Power to the Measurement Lines; 2.7 Turning Off the Instrument

2.2 Connecting the Measurement Lines
30
Example instrument loss calculation and connection method selection
The instrument's voltage input resistance and current input resistance are as follows:
Voltage input resistance: 2 M ±0.04 k (same for all ranges)
Current input resistance: For the 1 mA to 100 mA ranges, less than or equal to 520 m
For the 200 mA to 20 A ranges, less than or equal to 15 m
Depending on the magnitude of the input voltage and input current, instrument loss (loss caused by the input
resistance of the voltage inputs and the input resistance of the current inputs) will affect measured values.
Following are examples of how to calculate instrument loss for the PW3335 and an explanation of how to
choose the connection method.
Example 1: Input voltage of 100 V, current of 8 mA, and active power of 0.08 W (power factor of 0.1)
Method 1:
With Method 1, instrument loss is caused by the current input resistance of the current inputs.
Instrument loss = (Input current)
2
× (Current input resistance)
(1) Using the 10 mA range (with a current input resistance of 520 m)
Instrument loss = (0.008 A)
2
× 520 m = 0.03328 mW
(2) Using the 200 mA range (the range with the lowest current input resistance of 15 m)
Instrument loss = (0.008 A)
2
× 15 m = 0.00096 mW
Method 2:
With Method 2, instrument loss is caused by the voltage input resistance of the voltage inputs.
Instrument loss = (Input voltage)
2
÷ (Voltage input resistance)
= (100 V)
2
÷ 2 M = 5 mW
Connect the instrument using Method 1, which has the lower instrument loss. The instrument loss in this
configuration is 0.03328 mW (while using the 10 mA range) or 0.00096 mW (while using the 200 mA range).
Method 1
Method 2
Source Load Source Load
Voltage input
terminal
Current input
terminal
Source Load Source Load
Voltage input
terminal
Current input
terminal
Input resistance
Input resistance
Input resistance
Input resistance
Voltage input
terminal
Current input
terminal
Voltage input
terminal
Current input
terminal
Input resistance
Input resistance
Input resistance
Input resistance
Although it is possible to measure a current of 8 mA with the 200 mA range, which has an effective mea-
surement range of 2 mA to 300 mA, measurement accuracy will suffer. To make this measurement at a
higher level of accuracy, use a lower range that does trigger a peak value overage (i.e., one for which the
PEAK OVER I lamp does not light up).