Test Modes
The DLRO10HD features five test modes, selectable via a rotary switch on the instrument. Modes include normal, automatic, automatic unidirectional, continuous, and inductive.
To initiate normal mode, simply connect the test leads to the unit under test and press the "test" button. The instrument will perform continuity checks on all four connections and apply current in both forward and reverse directions. Results will then appear on-screen. A mode like this one with a multidirectional current will be ideal for testing dissimilar metals because it will cancel out the thermocouple effect.
In automatic mode, testing begins as soon as the instrument detects that probes have made contact with a test source. The DLRO10HD will then apply forward and reverse current and display the average value. This mode makes testing more streamlined, especially with the included DH4 handspikes, because there is no need to press "test" every time when testing multiple sources in quick succession.
Automatic unidirectional mode is similar to automatic mode in that testing begins when probes make contact. However, in this mode, current is only applied in one direction to make testing faster. Keep in mind that thermal EMF from dissimilar metal bonds can lower the accuracy of this test mode.
In continuous mode, tests are made repeatedly on the same sample as long as leads remain connected. Measurement data is updated every three seconds in this mode until the circuit is broken.
Inductive mode is useful when testing motors or generators, however, it requires the user to keep a close eye on voltage stability while the inductive element is charged. When test leads are connected to the test source and the "test" button is pressed, the DLRO10HD sends current through the test sample in one direction. As voltage stabilizes, readings will decrease to the true measurement value. This is where the operator must determine if the result is stable enough.