DLRO10 and DLRO10X
Digital Micro-Ohmmeters - Features

Description
The DLRO10 and DLRO10X set the standards for low resistance measurement. DLRO10 and DLRO10X are fully automatic instruments, selecting the most suitable test current up to 10 Amps DC to measure resistance from 0.1µΩ to 2000Ω, on one of seven ranges.

For user's who desire more control over the measurement process, DLRO10X uses a menu system controlled by a two-axis paddle to allow the user to manually select the maximum test current. The DLRO10X also adds real time download of results and on board storage for later download to a PC.

Both instruments are built into a strong, lightweight case that is equally at home in the field or in the laboratory. Light enough to be worn around the neck. The DLRO10 uses a large, bright 4 1/2-digit LED display while the DLRO10X has a large backlit LCD display.

Normally, measurements are made with forward and reverse currents to cancel the effects of any standing voltages across the test sample. The average value is then displayed within 3 seconds, to a basic accuracy of 0.2%. The model DLRO10X displays both forward and reverse measurements as well as the average of the two.

DLRO10X allows the user to set high and low pass limits, thereby enabling simple GO-NO-GO testing. At the end of a test the DLRO10X will store the test results, as well as any notes relevant to the test. The unit is fitted with RS-232 communications that will allow results to be downloaded in real time or stored for later retrieval. Up to 700 sets of results may be stored, complete with notes containing up to 200 characters.
 

• Auto current reversal cancels Standing EMF's.
• Protected to 600 Volts.
• Automatically detects continuity in potential and current connections.
• Multiple operating modes including fully automatic measurements.
• Alpha-numeric keypad for entering test notes (Model DLRO10X).
• User selectable High and Low Limits (Model DLRO10X).
• Printer output and memory (Model DLRO10X).

• Four terminal resistance method shows the true resistance of the item under test.
• Bright LED displays are easily visible under all lighting conditions.
• Automatically applies forward and reverse currents which cancel out any standing voltages across the sample under test.
• Checks for undue noise during measurement, reducing the possibility of recording the incorrect result.
• Automatically detects continuity in P and C circuits, preventing erroneously high reading to be taken due to high resistance contact.
• Battery module has a battery condition indicator allowing the user to check the state of spare batteries without connecting to the unit.
• The RS-232 communications port on the DLRO10X allows downloading of results in real time or stored for later retrieval.

Applications and Test Modes
The needs for accurate low resistance measurement are well known and very diverse. They range through Goods Receiving inspection of components to ground bonding and welding joints. Typical applications include, but are not limited to, making DC resistance measurements of:

• Switch and contact breaker resistance.
• Busbar and cable joints.
• Aircraft frame bonds and static control circuits.
• Integrity of welded joints.
• Inter-cell connections on battery systems up to 600 volt peak.
• Quality control of resistive components.
• Transformer and motor winding resistance.
• Rail and pipe bonds.
• Metal alloys, welds and fuse resistance.
• Graphic electrodes and other composites.
• Transmitter aerial and lighting conductor bonding.

The DLRO10 will display the average of the measurements achieved using forward and reverse current, while the DLRO10X displays both individual measurements and the average of both.

Any metallic joint can be measured but users must be aware of measurement limitations depending on application. For example, if a cable manufacturer plans to make resistive measurements on a thin wire, a low test current should be selected to prevent heating the wire thereby changing its resistance.

Measurements on electric motors and generators will be inductive and require the user to understand the inductive mode and charging process before a correct result is achieved. The DLRO10HD is well suited to measure thick conductors, bonds and quality of welding because of its 10A range for resistance values up to 250mΩ.

Electromagnetic noise induced into the leads can interfere with a reading. A noise symbol alerts the user and prevents a measurement when the instrument detects noise above its threshold.

When dissimilar metals are joined a thermocouple effect is created. Users should select a bidirectional mode to ensure cancellation of this effect. The instrument measures with current flowing in both directions and averages the result.

Normal mode is initiated by pressing the 'Test' button after connecting the test leads to the unit under test. Continuity of all four connections is checked. Current is applied in both forward and reverse direction following which measurement is displayed.

Automatic mode allows forward and reverse current measurements to be made and the average displayed simply by making contact with all four probes. This mode is ideal when working with the supplied handspikes. Each time the probes are removed and reconnected to the load another test will be performed without the need to press the test button on the instrument.

Continuous mode allows repeated measurements to be made on the same sample. Simply connect the test leads and press the test button. The measurement is updated every three seconds until the circuit is broken.

Inductive mode is intended for use when measuring inductive loads. When measuring inductive loads it is necessary to wait for the voltage to stabilize. This means that the measurement could take a few seconds or several minutes. The test leads are firmly connected to the item to be measured and the Test Button is pressed. The instrument will pass a current through the sample and wait for the voltage to stabilize. If possible the current will be increased. This procedure will be repeated until the voltage detected falls into the range 15mV to 200mV. The instrument will continue to take readings, which will gradually decrease to the true value as the voltage stabilizes further. The operator decides when the result is stable and presses the Test Button to terminate the test. Measurement is made with forward current only.

Uni-directional mode, (DLRO10X), applies a current in one direction only. This does not enable any standing EMF's to be negated but speeds up the measurement process. Test starts automatically when probes are connected.