5 Things to Know Before Buying insulation resistance tester

Trying to decide on an insulation resistance tester? Not sure exactly which model, what features, or what output test voltage you need?

Hengfeng contains other products and information you need, so please check it out.

There are six things to consider when deciding on the best insulation resistance tester for your needs, including:

1. What equipment needs to be tested?
2. What are the voltage requirements?
3. Where are the tests going to take place?
4. What questions will an insulation resistance tester help me answer?
5. What is the experience level of the technician performing the tests?
6. What role does safety play in selecting a new tool?

The insulation tester you choose should match your testing requirements. Many handheld insulation testers can supply test voltages up to volts.

A look at the products

Before examining these six issues, let’s look at the relevant products. (Use the scroll bar at the bottom of the chart to move right and left.)

What equipment needs testing?

First, make a list of the equipment that you expect to require insulation resistance testing. Write down the equipment's nominal voltage rating (found on the nameplate of the equipment) and the approximate number of insulation resistance tests that you plan to perform annually. The nominal voltage will help determine what test voltage is needed from the tester. The annual number of insulation resistance tests estimated may be surprising. When more tests need to be conducted, the overall quality, durability, and convenience features of the test instrument become more important.

What are the voltage requirements?

The output test voltage applied to equipment should be based on the manufacturer's recommended DC insulation resistance test voltage. If test voltage is not specified, use industry best practice data. (See the table for recommendations of the International Electrical Testing Association.) Make sure you choose an insulation resistance tester that will supply the needed output test voltage. Not all insulation resistance testers are the same: some will supply only up to 1,000 V DC, while others may supply 5,000 V DC test voltage or more.

Where are the tests going to take place?

Considering the testing environment and other possible uses for the insulation resistance tester will help in selecting additional features. For example, the ability to use one instrument for insulation resistance tests and as a typical digital multimeter can add convenience. Because all circuits and equipment must be verified as electrically de-energized before an insulation resistance tester is connected to the equipment, it is often less convenient to carry both a digital multimeter for voltage testing and an insulation resistance tester to various locations.

Nominal voltage rating of equipmentMinimum insulation resistance DC test voltageRecommended minimum insulation resistance in megohms,,,,,,,,,000

Recommended test voltages and minimum insulation values. The International Electrical Testing Association (NETA) provides representative test and minimum insulation values for various voltage ratings of equipment for use when manufacturer's data is not available.

When thinking about the environment for testing, ask yourself these questions:

• Will the insulation resistance tester be used for troubleshooting, preventive maintenance, or both?
• Where will the test instrument be used — only in a shop environment or in an industrial plant?

Some insulation resistance testers can be relatively large and not very portable, while others can be carried easily.

HVAC service technicians not only test for failed insulation, but they also commonly test for open fuses and failed capacitors. Technicians who often perform voltage checks, capacitor checks, temperature measurements, and insulation resistance tests may prefer a test tool that combines all these functions into one instrument. 

Consider also the features you need based on the type of insulation resistance test to be performed. In fact, this one question may come to mind: If you need only one simple insulation test, why purchase an insulation resistance tester at all, since a standard multimeter already has the ability to read resistance? To help answer that question and better understand some of the features that may be required in an insulation resistance tester, it is necessary to understand what happens in the process of measuring insulation resistance and what the test is designed to accomplish.

What you learn from an insulation resistance test

Insulation resistance testing puts a qualitative value on the condition of conductor insulation and the internal insulation of different pieces of electrical equipment. As an insulation resistance test begins, apply a DC voltage to the conductor or equipment under test. Some current flows out of the test equipment into the conductor and begins to charge the insulation. This current is called capacitive charging current and can be observed on the meter face.

As the charging current first begins to build, the resistance reading on the meter face will indicate a low value. Think of this as electrons beginning to flow into and become stored in the insulation itself. The more current that flows out of the test set, the lower the megohm reading. The insulation becomes charged quickly and the meter indication will begin to settle out at a higher megohm value, provided the quality of the insulation is good.

The next current that flows is the absorption — or polarization — current. The amount of absorption current is dependent upon the contamination of the insulation. For example, if moisture is present in the insulation, absorption current will be high, indicating a lower resistance value. However, it is important to realize this absorption current takes longer to build than the capacitive charging current. Therefore, an insulation tester operated for too short a period will observe only the capacitive charging current and not begin to show the presence of contaminants in the insulation.

Finally, the current that leaks through deteriorated insulation and into the non-current carrying metal components is the leakage current. This current is most often considered in an insulation resistance test. However, for more accurate troubleshooting and maintenance, the absorption or polarization current must also be considered. Some insulation resistance testers can be programmed to perform the tests needed to consider all currents.

Will you measure polarization current?

Since the polarization current takes longer to build, the insulation resistance tester must run for a longer period. The industry standard for this test is ten minutes. To help determine the contamination and overall condition of insulation, take a reading on the insulation resistance tester at one minute and another reading at ten minutes. The ten-minute reading is divided by the one-minute reading to provide the polarization index. As part of a routine maintenance program, you should record both spot reading test values and the polarization index values. Always compare the most recent readings to previous readings. The polarization index should never be less than 1.0.

Will you measure leakage current?

While all insulation resistance testers will indicate leakage current and provide the information to help estimate contamination of the insulation, for industrial environments you should consider those testers that automatically obtain this data. You obtain leakage current by applying the test voltage to the component under test, then taking a resistance reading after one minute. This is often called the spot reading test. The spot reading test allows capacitive charging currents to stabilize and is the industry standard to determine leakage current through insulation. Minimum insulation resistance values in megohms should be based on the spot reading test.

What is your experience level?

Any test instrument is only as good as the knowledge and experience level of the person using the equipment and interpreting its readings. When selecting an insulation resistance tester, consider the expertise of the individuals who will be performing the insulation resistance tests. Obviously, simplicity and limited functions should be considered if application needs and experience levels are minimal. However, training on insulation resistance testing need not be extensive. Manufacturers' manuals and basic texts are available to serve the purpose. For inexperienced personnel, consider on-the-job training for proper and safe use of insulation resistance testers. Make sure the insulation resistance tester purchased will meet the application needs for output test voltage and other functions. Then, provide training for those who will be performing the tests.

What role does safety play in testing and troubleshooting?

Safety is paramount when it comes to testing and troubleshooting. Because the insulation resistance tester produces significant DC voltages, it can never be connected to an energized circuit. Also, the output of the tester can destroy electronic circuits. Never connect an insulation resistance tester to electronic power supplies, PLCs, VSDs, UPS systems, battery chargers, or other solid-state devices. Some insulation resistance testers have a built-in type of warning system that will let technicians know when voltage is present on a circuit.

Like all test tools, insulation resistance testers should be rated for their application, suitable for the environment in which they will operate, and tested by a nationally recognized testing laboratory. If it will also be used as a multimeter, the insulation resistance tester should be category rated. Test leads should be durable, rated, and tested.

Insulation can hold a significant voltage charge for a period after the insulation resistance test is complete. Most testers will automatically discharge the insulation after the test is complete, but some will not. This is an important point to consider when selecting an insulation resistance tester. Some testers will indicate voltage levels as well as insulation resistance values. On such testers it is possible to watch the voltage level decay to zero after the test output voltage is shut off. Some manufacturers recommend the insulation resistance tester remain connected to the circuit or component under test after the test is complete for up to four times as long as the test was conducted to ensure safe discharge. Most technicians will ground the circuit under test after the test is complete to verify the insulation is discharged. Research the tester's self-discharge feature carefully when selecting an insulation resistance tester.

The next step in selecting your insulation resistance tester

The selection of the best insulation tester is crucial when dealing with electrical equipment like cables, motors, and appliances. Insulation resistance is the barrier that prevents potential hazards such as short circuits, overheating, or fires. But what exactly is insulation resistance testing, and how can it safeguard your electrical systems? In this guide, we’ll explore the essentials of insulation testing, explain its importance for your equipment, and guide you in choosing the best insulation tester. Are you ready to protect your electrical systems with the right tools?

what is testing for insulating resistance?

But what is testing for insulating resistance, and how does it operate? Testing for insulating resistance is a crucial aspect of maintaining and ensuring the safety of electrical systems. This process involves assessing the resistance level of electrical insulation used in components such as cables, transformers, motors, and switchgear. This testing aims to verify that the insulation is in good condition and performing its protective role effectively, thereby minimizing the risk of electrical malfunctions, fires, and other hazards.

Insulation resistance testing is a method used to determine how well an insulating material can resist the flow of electric current. The process involves applying a specified DC voltage, known as a dielectric, across the insulating material and then measuring the amount of leakage current that passes through or around it. This measurement provides insight into the condition of the insulation and its ability to prevent electrical leakage.

Importance of Insulation Testing

The importance of insulation testing can be highlighted in several key areas:

• Prevention of Electrical Shocks: One of the primary purposes of insulation is to provide a barrier between live electrical components and the environment, protecting users from harmful electric shocks. Insulation testing ensures that this barrier remains intact and effective.
• Fire Hazard Reduction: Insufficient or degraded insulation can lead to short circuits, which in turn can cause overheating and fires. Regular insulation testing helps identify potential weak spots, thereby preventing such dangerous incidents.
• Prolonging Equipment Life: Insulation degradation is a common cause of premature equipment failure. By regularly testing insulation, potential issues can be detected and addressed before they lead to significant damage, thus extending the lifespan of electrical equipment.
• Cost Efficiency: Early detection of insulation problems through regular testing can prevent costly repairs or replacements. This proactive approach saves money by avoiding major breakdowns and extending the operational life of the equipment.
• Meeting Industry Standards: Many industries are subject to strict regulations regarding electrical safety. Insulation testing is often a mandatory requirement to comply with these standards, ensuring that the equipment operates safely and legally.
• Insurance Compliance: Some insurance policies require regular insulation testing as part of their terms. Conducting these tests helps ensure that insurance coverage remains valid and that your business is protected in case of an incident.
• Minimizing Downtime: Insulation failure can lead to unplanned downtime, which can be particularly costly in industrial settings. Regular insulation testing allows for planned maintenance, reducing the risk of unexpected outages and ensuring continuous operation.
• Ensuring Consistent Performance: Reliable insulation is essential for the consistent performance of electrical equipment. Regular testing helps maintain this reliability, preventing unexpected failures that could disrupt operations.
• Trend Analysis: By conducting regular insulation tests and tracking the results over time, it is possible to identify trends that indicate gradual insulation degradation. This data-driven approach allows for more accurate maintenance scheduling and better resource allocation.
• Predictive Maintenance: Insulation testing can be a key component of a predictive maintenance strategy, where potential issues are identified and resolved before they cause significant problems, thus avoiding costly downtime and repairs.

How to Choose an Insulation Resistance Tester

You should take into account a number of elements when selecting an insulation resistance tester, including features, performance, cost, and warranty. Additionally, you ought to contrast several models to observe how they vary in these areas. Here are some key factors to consider when choosing an insulation tester:

Want more information on tan delta tester? Feel free to contact us.

1. Voltage Range

Application Requirements: The insulation tester should have a voltage range that suits the equipment you are testing. For instance, if you are working with low-voltage systems, a tester with a range of up to 1 kV might suffice. For high-voltage equipment, you may need a tester capable of delivering up to 10 kV or more.

Multiple Voltage Settings: Choose a tester that offers multiple voltage settings, allowing flexibility to test a variety of equipment with different insulation requirements.

2. Resistance Measurement Range

Wide Resistance Range: Ensure the tester can measure a broad range of resistance values. A good tester should be able to measure resistance from a few kilohms (kΩ) up to several teraohms (TΩ), as different equipment will have different insulation resistance requirements.

Accuracy: Consider the accuracy of the tester at different resistance levels. Higher accuracy is essential for reliable measurements, especially when testing critical equipment.

3. Testing Features

PI and DAR Tests: Look for a tester that can perform Polarization Index (PI) and Dielectric Absorption Ratio (DAR) tests. These tests provide more detailed information about the insulation condition over time, which is crucial for predictive maintenance.

Step Voltage Testing: This feature applies different voltages in steps and measures the insulation resistance at each level, helping to identify insulation weaknesses that may not be apparent at a single voltage.

4. Safety Features

Safety Standards Compliance: Ensure the insulation tester complies with international safety standards, such as IEC or UL. This compliance guarantees that the device is safe to use, even in demanding environments.

Overload Protection: Choose a tester with overload protection to prevent damage to the device and ensure user safety in case of accidental overvoltage.

5. Ease of Use

User Interface: Look for a tester with a clear, easy-to-read display and intuitive controls. A tester with a backlit screen is helpful for working in low-light conditions.

Portability: Consider the size and weight of the tester, especially if you will be using it in the field. A portable and lightweight tester is easier to carry and use in different locations.

6. Data Logging and Connectivity

Memory Storage: Some insulation testers come with built-in memory to store test results. This feature is useful for tracking measurements over time and for generating reports.

Connectivity Options: Modern insulation testers may offer USB or wireless connectivity, allowing you to download test data directly to a computer or mobile device for analysis and reporting.

7. Battery Life and Power Options

Long Battery Life: If you are working in the field, consider a tester with a long battery life to avoid interruptions during testing. Some models also offer rechargeable batteries.

Power Supply Options: Some testers can be powered by AC mains, which can be beneficial for extended testing sessions in a fixed location.

8. Brand and Support

Reputable Brand: Choose a tester from a reputable manufacturer known for quality and reliability. Brands like Fluke, Megger, and Kyoritsu are well-regarded in the industry.

Warranty and Support: Check the warranty period and the availability of customer support and service centers. A good warranty and responsive support can save time and money in the long run.

9. Budget Considerations

Cost vs. Features: While it’s important to stay within budget, ensure that the tester you choose has all the necessary features for your application. Sometimes, investing a bit more upfront can save money by preventing future equipment failures.

Long-Term Value: Consider the long-term value of the tester in terms of durability, support, and how well it meets your ongoing testing needs.

Top Features of Insulation Resistance Testers from Leading Brands

The table below provides a general comparison between three well-known brands: Fluke Insulation Tester, Megger Insulation Tester, and Kyoritsu Insulation Tester

Feature Megger Fluke Kyoritsu Test Voltage Range 250V to 10kV 50V to 10kV 250V to 5kV Resistance Measurement Range Up to 35 TΩ Up to 2 TΩ Up to 5 TΩ Measurement Accuracy ±5% reading + ±1 digit ±5% reading + ±2 digits ±5% reading + ±2 digits Test Features PI, DAR, Step Voltage, Dielectric Discharge PI, DAR, Ramp Test PI, DAR, Step Voltage Safety Features IEC Standards, Overload Protection IEC Standards, Overload Protection IEC Standards, Overload Protection User Interface Large digital display with backlight Large digital display with backlight Large digital display with backlight Data Storage Internal memory for storing results Internal memory and PC connectivity Limited internal memory Connectivity USB, Data Management Software USB, Bluetooth, Data Management Software Limited to wired connection Battery Life Long-lasting with rechargeable option Long-lasting with rechargeable option Decent battery life Price Mid to High Mid to High Economical to Mid Support and Service Excellent, with multiple service centers Excellent, with multiple service centers Good, with less coverage in some areas

Top rated insulation testers

Here’s a list of some of the most highly regarded insulation testers in the market:

1. Fluke FC Insulation Multimeter

The Fluke FC is versatile, reliable, and user-friendly, making it a favorite among electricians and engineers.

• Combines a digital insulation tester with a full-featured, true-RMS digital multimeter.
• Insulation test range: 0.01 MΩ to 2 GΩ.
• Insulation test voltages: 50 V, 100 V, 250 V, 500 V, V.
• Built-in PI/DAR calculations for assessing insulation quality.
• Compatible with the Fluke Connect app for remote monitoring.

2. Megger MIT525 Insulation Resistance Tester

Known for its accuracy and ruggedness, the MIT525 is widely used in industrial settings for testing high-voltage equipment.

• Test voltage up to 5kV with insulation resistance up to 10 TΩ.
• Provides advanced diagnostic capabilities, including polarization index (PI), dielectric absorption ratio (DAR), and step voltage testing.
• Durable design with a robust carrying case.
•  Includes both USB and Bluetooth connectivity for data transfer.

3. Kyoritsu KEW Insulation Testers

The Kyoritsu KEW is a robust insulation tester known for its high voltage capability and advanced diagnostic features.

• Offers test voltages from 500V to 12kV.
• Can measure up to 35 TΩ, making it suitable for testing high-voltage equipment.
• Capable of storing up to measurement results, with USB connectivity for data transfer.

4. Chauvin Arnoux CA

The Chauvin Arnoux CA is another top-rated insulation tester, known for its high accuracy and advanced testing capabilities in professional applications.

• Offers test voltages up to 10kV.
• Capable of measuring insulation resistance up to 30 TΩ

5. Hioki IR-20 Insulation Tester

Hioki’s IR-20 is known for its speed, accuracy, and safety features, making it a popular choice for quick diagnostics.

• Provides five test voltages: 50V, 125V, 250V, 500V, V.
• Insulation resistance up to 4 TΩ.
• Fast response time with automatic discharge after testing.
• Dual display for simultaneous readings.

7. Extech Digital Insulation Tester

The Extech is well-regarded for its affordability and reliability, making it an excellent choice for both professionals and DIY users.