UNI-T UT620C Digital Micro Ohm Meter Operating Manual

I. Safety Information

• ⚠️ Pay special attention to safety when using the product.
• Do not measure any live object. Make sure that the resistor or metal object to be measured is de-energized before measurement, otherwise, it may damage the product.
• When ? low battery symbol appears, please charge the product in time (the charging time is 5~8 hours).
• Please charge the battery once a month or two months if the product is not used for a long time.
• Please stop use immediately in case test lead is broken during use.
• Do not place or store the product in environments with high temperature, high humidity, dews, and direct sunlight for a long time.
• Perform regular maintenance, keep product and test leads clean. Avoid drop or impact.
• Use, dismantling or repair shall be performed by authorized professional.
• If danger caused by the product occurs, please stop use and seal the product immediately, and send it to authorized center for maintenance.
• The symbol "⚠️" affixed at product and shown in user manual indicates user must operate according to the instruction.

II. Overview

The Digital Micro Ohm Meter (also known as Micro Ohm Meter, Ohm Meter, and DC Resistance Tester) adopts micro-processor technology and 4-wire testing method to make measurement safe, accurate and reliable. The meter is mainly applied to measure resistance of conductor, contact resistance of switch, connector and relay, resistance and contact resistance of coil, motor and transformer winding. It can also test connection resistance and low resistance between metal parts, resistance and contact resistance of connecting conductors between grounding electrode of ground grid. The product consists of meter, monitoring software, test leads, communication cable, etc. Featuring a large LCD, the tester enables user to view the data easily. It can store 500 groups of data. The measured resistance ranges from 0.001mΩ to 300.0kΩ. The software of master computer has multiple functions including data viewing, data accessing, data storage, report generation, etc.

III. Range and Accuracy

Note: ±0.2%FS±20dgt (18°C~28°C; >70%rh / -10°C~50°C; <80%rh)

IV. Technical Specifications

V. External Structure

Diagram showing the external structure of the UNI-T UT620C Digital Micro Ohm Meter:

• 1. USB transmission/charging port ?
• 2. Charging indicator light
• 3. Connectors for test leads
• 4. LCD display
• 5. Rubber insulation protector
• 6. Functional buttons ⚙️
• 7. Test leads (red: 1pc; black: 1pc)

The device features a DC/USB port, input terminals labeled C1, P1, P2, C2, an LCD display, and several functional buttons.

VI. Operating Instructions

1. Power on/off

Press the ⏻ button to power on/off the meter. The "APO" [auto power off] symbol appears on the bottom right corner of the LCD after the meter powers on. The meter powers off automatically after 15 minutes of inactivity.

2. Check battery voltage

If the ? [low battery] symbol appears on the LCD after the meter turns on for 2 to 4 seconds, it indicates the battery voltage is low. Please charge the battery in time. Sufficient battery voltage ensures measurement accuracy. The battery indication bars decrease as the battery voltage decreases.

3. Resistance precision testing

Please clear the insulation layer and the oxidation layer on the surface of the object to be measured before test. Do not perform live test for resistance or DC low resistance. Live test may damage the meter. Test clips may be oxidized after they are used for a long time. To ensure good contact of clips, please clear the oxide and the foreign object at the clips. Make sure the connection between test leads and tester/measured object are reliable. Component heat during test may cause error, thus it is recommended to perform test for 30 seconds, with testing interval at 30 seconds. If the "OL" [overload] symbol appears during test, it indicates the resistance between measured points exceeds the range. Please restart the meter and then retest to troubleshoot fault caused by overload protection. If the fault is caused by overload protection, it indicates the measured resistor is energized; please de-energize the measured resistor immediately and restart the meter for retesting. Or please check if poor contact of test leads occurs (the circuit between measured points may be open).

Measuring resistance by connecting the meter with the resistor:

Diagram shows the meter connected to a "Measured resistor RX" using red and black test leads. The meter displays "OL" indicating overload.

Measuring the resistance between electric meter and down conductor:

Diagram shows a setup for measuring resistance between an electric meter (connected to a grounding wire of electric meter, copper busbar, and equipment grounding wire) and a down conductor. Red and black test leads connect the meter to these points. The meter displays "OL".

Measuring the resistance between metal connectors:

Diagram shows the meter connected to "Metal connectors" using red and black test leads. The meter displays "OL".

4. Backlight control

In power-on state, press the ? button (or similar function button) to turn on/off backlight. The backlight function applies in dark environments. The default state of backlight is off when powering on the meter.

5. Data hold/storage

After the meter is powered on or measurement is completed, press the [hold] button (labeled HOLD) to hold the current displayed data. Press the [memory] button (labeled MEM) to perform numbering automatically and store current displayed data. The "FULL" [full storage] symbol appears on the LCD if storage is full. As shown below, the measurement data is 70.11mΩ, it is held when the [hold] button is pressed.

LCD Display Examples:

• Display showing "R 70.11 mΩ", "DH", "APO", and battery indicator.
• Display showing "FULL".
• Display showing "R 70.11 mΩ", "MEN" (likely a typo for MEM), "APO", and battery indicator.

6. Data viewing/deletion

After the meter is powered on or measurement is completed, the meter switches to data viewing mode and "MR" [memory read] appears on the LCD when the [mode] button (labeled MODE) is pressed. Press the [up] ▲ or [down] ▼ buttons to set the step as 1 (group), press the [left] ◀ or [right] ▶ buttons to set the step as 10 (groups). Press the [mode] button (labeled MODE) or the [power] ⏻ button for twice to exit the mode and return to testing mode. As shown below, the number "1" at top right is the number of group. If no data is stored, "NULL" appears on the LCD.

LCD Display Examples:

• Display showing "R 70.11 mΩ", "MR", "APO", and battery indicator.
• Display showing "NULL".

In data viewing mode, press the [mode] button (labeled MODE) to switch to data deletion mode. Press the [left] ◀ or [right] ▶ buttons to select "NO" or "YES". When pressing "NO" and then pressing the [power] ⏻ button, the data will not be deleted and the meter returns to testing state. Press "YES" and then press the [power] ⏻ button to delete all stored data. After deletion, the display is showed as below:

LCD Display Examples:

• Display showing "DEL", "NO", and "DEL".
• Display showing "DEL", "YES", and "DEL".

7. Data upload

Connect the meter with computer via USB cable, turn on the meter, then operate the software of master computer. If USB connection is successful, the stored data can be viewed, uploaded and saved. The software of master computer has multiple functions including data viewing, data accessing, data storage, etc.

8. Line resistance calibration (clear residual resistance)

Short-circuit both clips first, then long press the [up] ▲ button for 2 to 3 seconds after the displayed value is stabilized, to complete calibrating line resistance, as shown below: Note: Only when the displayed value is stabilized can the [up] ▲ button be pressed.

Diagram shows the red and black test leads short-circuited, connected to the meter which displays "OL".

VII. Battery Description

The charging time is 5~8 hours typically. Please charge the battery once a month or two months if the product is not used for a long time. ⚠️ Charge the battery with the equipped original charger. The product does not support fast charging. The charger lights up red when charged and lights up green after charged fully. The product is powered by 3.7V lithium battery. If the battery voltage decreases, the battery indication bars will decrease and the ? [low battery] symbol will appear on the LCD. In such situation, please charge the battery in time. Low battery voltage can affect measurement accuracy.

VIII. Packing List

Note: The content of this user manual cannot be used as a reason for using the product for special purposes. The company is not responsible for other losses caused by use. The company reserves the right to modify the contents of the user manual. If there are changes, no further notice will be given.