Two Channel Measurements - Innova DS200 User Manual

Two Channel Measurements

Measuring Small Resistances/Calibrating a Current Shunt
Your DS200 Multimeter is capable of reading any two of its three channels simultaneously.
NOTE: Measurements using the internal current shunt will experience a degree of
crosstalk due to the impedance of the Common lead. Other measurement types
will also experience this crosstalk, but it should be negligible.
MEASURING SMALL RESISTANCES / CALIBRATING A CURRENT
SHUNT
The DS200 Multimeter can be used to measure small resistances in a live circuit. The
meter simultaneously measures the current and the corresponding voltage with the
precision voltage channel (Ω), and then finds the slope to calculate resistance.
This can be done with either the internal current shunt or an external current clamp.
Using a current clamp allows the measurement to be done without breaking the circuit
and allows for test currents above 10 Amps.
Wire the meter in as shown and enable the measurement mode. Apply a test current
and run the analysis.
The analysis works best with several points along the curve. Therefore, the optimal test
current has a large magnitude and a strong time varying component below 1kHz. Often
this test current can be the current already present within the system due to normal
operation. For example, an AC system's steady state or a DC systems startup transient
may provide sufficient data.
Figure 7: Current Clamp and Current Shunt Comparison
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