Metrix+ DIT 918 Insulation Resistance Tester 100V-1000V Megger

A. Product Overview

The Metrix Plus DIT 918 is a portable digital insulation resistance tester designed for checking the quality and condition of electrical insulation.

Insulation resistance testing helps technicians determine whether insulation around electrical conductors and equipment is providing sufficient resistance against unwanted leakage current.

The DIT 918 provides five insulation test voltage selections:

• 100V
• 250V
• 500V
• 1000V
• 2500V

Its insulation resistance measurement ranges are:

• 100V: 0 to 199.9 MΩ
• 250V: 0 to 499.9 MΩ
• 500V: 0 to 999.9 MΩ
• 1000V: 0 to 19.9 GΩ
• 2500V: 0 to 49.9 GΩ

The specified insulation resistance accuracy is ±5 percent of reading and ±5 digits. It also measures AC and DC voltage between 30V and 600V with 1V resolution. 

Key Features

• Digital insulation resistance measurement
• Test voltage up to 2500V
• Resistance measurement up to 49.9 GΩ
• AC and DC voltage measurement
• Backlit LCD display
• Automatic discharge function
• Live wire warning with audible indication
• Automatic power off
• Low voltage indication
• CAT III 600V safety category
• Battery operated portable design
• Supplied with test wires and alligator clips

B. Working Principle

The DIT 918 works by applying a controlled DC test voltage across the insulation being tested.

When the selected test voltage is applied, a very small current may flow through the insulation. The tester evaluates this current in relation to the applied voltage and calculates the resulting insulation resistance.

The relationship is based on Ohm's law:

Resistance = Voltage divided by Current

Healthy insulation normally presents very high resistance, often in the megaohm or gigaohm range.

If insulation has deteriorated because of factors such as moisture, ageing, contamination or physical damage, the measured insulation resistance may decrease.

Typical Testing Process

1. Isolate the equipment from its normal electrical supply.

2. Connect the test leads to the points specified by the applicable testing procedure.

3. Select the appropriate insulation test voltage.

4. Apply the test voltage.

5. Read the insulation resistance value on the LCD.

6. Compare the measured value with the equipment requirement or applicable maintenance standard.

7. After testing, the automatic discharge function helps discharge stored electrical energy.

The DIT 918 also incorporates a live wire warning with audible indication, helping alert the operator when voltage is present. 

C. Why Is the Metrix Plus DIT 918 Used?

1. Insulation Resistance Testing

The primary purpose of the DIT 918 is to measure high electrical resistance and evaluate insulation condition.

2. Preventive Electrical Maintenance

Periodic insulation testing can help maintenance teams identify deterioration before it develops into a more serious electrical problem.

3. Motor Insulation Testing

Insulation resistance testers are commonly used during maintenance checks on electrical motors and motor windings.

4. Cable Insulation Testing

Electrical cables can be checked for deterioration, moisture ingress or insulation problems.

5. Transformer Maintenance

Insulation testing can form part of electrical maintenance procedures for transformers and associated equipment.

6. Electrical Panel Inspection

Technicians may use insulation resistance testing when commissioning or maintaining electrical panels and circuits.

7. Installation Verification

New electrical installations may require insulation resistance checks as part of commissioning and verification procedures.

8. Fault Investigation

Low insulation resistance can indicate deterioration or leakage paths within an electrical system, helping technicians investigate possible electrical faults.

9. High Resistance Measurement

With measurement capability reaching 49.9 GΩ at the 2500V test setting, the DIT 918 is designed for high resistance insulation measurements. 

D. Suitable Buyers

The Metrix Plus DIT 918 Digital Insulation Tester is suitable for professionals involved in electrical testing, installation, maintenance and troubleshooting.

Typical users include:

• Electrical engineers
• Electricians
• Electrical maintenance technicians
• Industrial maintenance departments
• Electrical contractors
• Motor maintenance companies
• Motor rewinding workshops
• Control panel manufacturers
• Electrical panel technicians
• Facility maintenance teams
• Manufacturing plants
• Power distribution maintenance teams
• Transformer service companies
• Cable installation contractors
• Machine maintenance engineers
• HVAC electrical maintenance teams
• Automation companies
• Electrical testing laboratories
• Engineering service companies
• Preventive maintenance contractors

Frequently Asked Questions

1. What is the Metrix Plus DIT 918?

The Metrix Plus DIT 918 is a digital insulation resistance tester designed to measure high resistance electrical insulation using test voltages up to 2500V.

2. What test voltages are available in the DIT 918?

The instrument provides 100V, 250V, 500V, 1000V and 2500V insulation test voltage selections. 

3. What is the maximum insulation resistance range?

The highest specified measurement range is 0 to 49.9 GΩ at the 2500V setting. 

4. Can the DIT 918 measure AC voltage?

Yes. It supports AC voltage measurement from 30V to 600V.

5. Can the DIT 918 measure DC voltage?

Yes. The specified AC and DC voltage measurement range is 30V to 600V. 

6. What is the insulation resistance accuracy?

The specified accuracy is ±5 percent of reading and ±5 digits. 

7. Is the DIT 918 a 2500V insulation tester?

Yes. The highest available insulation test voltage is 2500V.

8. Can the DIT 918 be used as a digital megger?

Yes. In common industrial terminology, a digital insulation resistance tester is often referred to as a digital megger.

9. Does the DIT 918 have automatic discharge?

Yes. The tester includes an automatic discharge function. 

10. Why is automatic discharge important?

Insulation testing can leave electrical energy stored in the equipment being tested. The discharge function helps remove residual charge after the test.

11. Does the DIT 918 provide a live circuit warning?

Yes. It includes a live wire warning system with audible indication. 

12. Does the tester have a backlit display?

Yes. The DIT 918 has a backlit LCD display for easier reading.

13. What is the safety rating of the DIT 918?

The instrument is specified to IEC 61010-1 CAT III 600V, while the test leads are specified according to IEC 61010-031 with Pollution Level 2. 

14. What is the maximum short circuit current?

The specified maximum short circuit current is 1.3 mA. 

15. What type of batteries does the DIT 918 use?

It operates using six AA batteries