1. Introduction
The UNI-T UT500 series digital insulation resistance testers, including the UT501C model, are advanced instruments designed for measuring insulation resistance, alternating voltage, and other electrical parameters. Featuring a new design, large-scale integrated circuit, and digital circuit technology, these testers offer comprehensive functions, high accuracy, stable performance, and user-friendly operation. The UT501C is an essential tool for maintenance, testing, and verification of various electrical equipment, suitable for measuring insulation resistance in transformers, motors, cables, switches, and other electrical appliances.
Figure 1: UNI-T UT501C Insulation Resistance Tester
2. Key Features
- Insulation resistance measurement
- AC voltage measurement
- Buzzer alarm for low insulation
- Backlight display for clear readings in various lighting conditions
- Automatic shutdown to conserve battery life
- Voltage reminder for safety
- Data Hold function
- Auto Discharge feature for safety after high voltage tests
- Overrange Indication
- Low Battery Indication
- Self-Lock Function for continuous testing
3. Specifications
| Parameter | Description |
|---|---|
| Model Number | UT501C |
| Display Type | Digital Only |
| DIY Supplies | Electrical |
| Brand Name | UNI-T |
| Origin | Mainland China |
| Certification | CE, FCC, RoHS |
| Output Voltage | 100V, 250V, 500V, 1000V |
| Insulation Resistance Measurement Range | 0.00MΩ - 5.00GΩ (up to 20GΩ for UT502C, UT501C up to 5GΩ) |
| Accuracy Class | 1 |
| Testing Voltage | 30V-750V (AC) |
| Short-Circuit Current | <2mA |
| Power Source | 6 x 1.5V AA alkaline batteries |
| Dimensions | 183.5mm x 115mm x 74mm |
| Product Weight | 0.6kg |
| Operating Temperature & Humidity | 0℃~35℃, <75% RH |
| Storage Temperature & Humidity | -20℃~60℃, <80% RH |
| Altitude | ≤2000 m |
| Rating | CAT III 600V |
Figure 2: Detailed Specifications Table
4. Package Contents
The standard package for the UNI-T UT501C Insulation Resistance Tester includes:
- 1 x UNI-T UT501C Insulation Resistance Tester
- 1 x Pair of Test Leads (Red and Black)
- 1 x Pair of Alligator Clips (Red and Black)
- 1 x Carrying Bag
- 1 x User Manual
Figure 3: Included Accessories
5. Safety Information
Please read and understand all safety warnings and operating instructions before using this instrument. Failure to observe safety precautions may result in electric shock, injury, or damage to the instrument.
- Always inspect the instrument, test leads, and accessories for any damage before use. Do not use if damaged.
- Ensure the battery compartment is securely closed before operation.
- Do not apply voltage to the input terminals that exceeds the maximum rated voltage (CAT III 600V).
- Be cautious when working with high voltages. Always assume circuits are live until proven otherwise.
- Do not operate the instrument in explosive atmospheres or in the presence of flammable gases or dust.
- Keep fingers behind the finger guards on the test probes during measurements.
- The instrument is designed for indoor use and at altitudes up to 2000m.
- The device is certified with CE, FCC, and RoHS standards.
6. Setup
6.1 Battery Installation
- Ensure the tester is turned OFF.
- Locate the battery compartment cover on the back of the instrument.
- Use a screwdriver to open the battery compartment.
- Insert six (6) 1.5V AA alkaline batteries, observing the correct polarity markings inside the compartment.
- Replace the battery compartment cover and secure it with the screw.
Figure 4: Battery Installation
6.2 Connecting Test Leads
Connect the test leads to the appropriate terminals on the tester:
- Connect the red test lead to the "LINE" terminal.
- Connect the black test lead to the "EARTH" terminal.
- For 3-wire measurements, connect the green test lead to the "GUARD" terminal.
7. Operation
7.1 Power On/Off and Mode Selection
Turn the rotary switch to the desired measurement function (e.g., 100V, 250V, 500V, 1000V for insulation resistance, or ACV for AC voltage measurement). To turn off the device, rotate the switch to the "OFF" position.
7.2 AC Voltage Measurement
- Turn the rotary switch to the "ACV" position.
- Connect the test leads to the circuit or component where you want to measure AC voltage.
- Read the voltage value displayed on the LCD.
Video 1: Demonstrates AC voltage measurement (0:00-0:06)
7.3 Insulation Resistance Measurement
- Ensure the circuit or device under test is de-energized and safely discharged before connecting the tester.
- Turn the rotary switch to the desired test voltage (100V, 250V, 500V, or 1000V).
- Connect the test leads to the points where insulation resistance is to be measured. For example, between a conductor and ground, or between two conductors.
- Press and hold the "PRESS TO TEST" button. The measurement will begin.
- For continuous measurement, press the "LOCK" button while holding "PRESS TO TEST". Release "LOCK" to stop.
- Read the insulation resistance value on the LCD. An audible alarm will sound if the insulation resistance is below a certain threshold (e.g., 4 MΩ).
- After the test, the instrument will automatically discharge any residual charge from the circuit under test.
Figure 5: Insulation Resistance Measurement in progress
Video 1: Demonstrates cable insulation resistance measurement (0:07-0:20), motor insulation resistance measurement (0:21-0:30), and transformer insulation resistance measurement (0:31-0:53).
8. Maintenance
8.1 Cleaning
Wipe the case with a damp cloth and mild detergent. Do not use abrasives or solvents. Ensure the instrument is completely dry before use.
8.2 Battery Replacement
When the low battery indicator appears on the display, replace all six (6) 1.5V AA alkaline batteries as described in the Setup section (6.1 Battery Installation).
8.3 Storage
If the instrument is not used for a long period, remove the batteries to prevent leakage. Store the device in a cool, dry place within the specified storage temperature and humidity range (-20℃~60℃, <80% RH).
9. Troubleshooting
- No display or dim display: Check if the batteries are correctly installed and have sufficient charge. Replace batteries if necessary.
- Incorrect readings: Ensure test leads are properly connected and not damaged. Verify that the correct measurement function is selected for the task.
- "OL" or Overrange Indication: This indicates that the measured value exceeds the instrument's maximum measurement range for the selected function.
- Buzzer alarm during insulation test: This indicates that the insulation resistance is below the safety threshold, suggesting a potential insulation fault.
10. User Tips
- Safety First: For enhanced safety, especially when working with high voltages, consider installing the device within a flame-retardant enclosure if there's a risk of deterioration or unexpected events.
- Insulation vs. Grounding: The UT501C is primarily an insulation resistance tester and AC voltage meter. It is not designed for measuring grounding resistance directly. For grounding resistance measurements, a dedicated earth ground resistance tester is required.
- Certifications: The UT501C is certified with CE, FCC, and RoHS, ensuring it meets relevant safety and environmental standards.
11. Warranty and Support
For warranty information, technical support, or service inquiries, please refer to the contact information provided with your purchase or visit the official UNI-T website. Keep your purchase receipt as proof of purchase.
