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The Extech 380560 (117V) or 380562 (220V) is a high-resolution benchtop milliOhm meter designed for precise resistance measurements. This instrument is particularly useful in applications requiring accurate low-resistance readings, such as testing transformers, motor coils, and PC boards. Its core function is to measure resistance across seven different ranges, offering a resolution as fine as 0.01mΩ, which allows for the detection of very small variations in resistance.
A key feature of this meter is its 4-wire Kelvin clip connection. This type of connection is crucial for ensuring optimum accuracy in low-resistance measurements. By separating the current-carrying leads from the voltage-sensing leads, the Kelvin method effectively eliminates the influence of lead resistance and contact resistance from the measurement. This means that the meter measures only the resistance of the device under test, providing a more precise and reliable reading. The DC test current flows from the FORCE+ terminal to the FORCE- terminal, while the S+ and S- (SENSE) terminals measure the DC voltage drop across the device. The meter then calculates and displays the resistance based on the measured voltage and the test current (Rx = Vx / Is).
The device incorporates a built-in comparator feature, which is a significant usage feature for quality control and sorting applications. This HI-LO-GO testing capability allows users to program specific high and low resistance limits. When a measurement is taken, the meter compares the reading against these programmed limits and indicates whether the resistance is too high (HI), too low (LO), or within the acceptable range (GO). This is visually indicated by HI, LO, and GO status LEDs on the front panel. For added convenience, the comparator function can be configured to sound an audible tone for each "GO" measurement, providing immediate feedback without requiring constant visual monitoring. The comparator limits are easily adjustable via dedicated screws on the front panel, accessed by positioning the SET/TEST pushbutton to SET and the LO/HI pushbutton to either LO or HI.
Operating the meter is straightforward. After connecting the Kelvin test leads to the meter and pressing the POWER pushbutton, users can select the desired measuring range using the black pushbuttons. If the resistance of the device under test is unknown, it is recommended to start with the highest range and work downwards to avoid potential over-range conditions. The meter's LED display will show "1 _" to indicate an over-range condition. To check the meter's zero, the test leads can be clipped together. The SET/TEST pushbutton allows users to switch between the test mode and the comparator setting mode.
The meter's design emphasizes ease of use and clear indication. The large LED display provides a clear digital readout of the resistance value. The HI/LO/GO status indicators are prominently placed to give quick visual feedback on comparator results. Power and range selection are managed through intuitive pushbuttons. The Kelvin clip leads connect to clearly labeled input terminals on the front of the device.
In terms of maintenance, the device is designed for years of reliable service with careful use. While specific user-level maintenance beyond proper handling and storage is not detailed, the robust construction and the 4-wire measurement principle contribute to its long-term accuracy. The replacement Kelvin leads (model 380465) are available, indicating that these components are considered wear items that can be replaced to maintain the meter's functionality. Annual calibrations are recommended to verify the meter's performance and accuracy, ensuring that it continues to provide reliable measurements over time. Extech offers calibration and repair services, including NIST traceable calibration, to support this maintenance requirement. Users should ensure the meter is connected to the correct power source (110V for model 380560 or 220V for model 380562) and, critically, should never apply voltage to the meter input terminals, as this can cause damage. The power cable input and an audible alert button are located on the rear of the instrument for convenience.
General| Model | 380560 |
|---|---|
| Category | Measuring Instruments |
| Type | Multimeter |
| Display | LCD |
| Diode Test | Yes |
| Continuity Test | Yes |
| Data Hold | Yes |
| Auto Ranging | Yes |
| Battery Type | 9V |
| Temperature Range | -40°C to 1000°C |
| Safety Rating | IEC 61010-1 |
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