What Is an Electrical Test?

Why Is it Important to Perform Electricity Tests?

Electrical testing is critical for understanding the way electrical charges move through a material and across its surfaces. Electrical testing methods can be used to quantify electrical currents, test a circuit, identify and troubleshoot conductivity issues, and measure the efficacy of insulation materials. Electrical testing of all types are vital for ensuring a safe and effective end application.

Materials Conduct Electricity Differently

When it comes to electrical conductivity, not all materials are created equal. Some materials transfer electricity, heat, and sound easily, while others do not.

The electrical conductivity of a given material is determined by several factors: density, temperature, and the presence of free ions. Materials with free ions allow for smooth current flow because those ions and atoms are bound by attractive electrostatic forces.

Non-conductive materials are often referred to as “insulators.” Examples of insulators include rubber, wood, plastic, and glass. Highly conductive materials are usually called “conductors.” Common conductors include copper, graphite, and, surprisingly, the human body. A third category, “semiconductors,” refers to materials that offer moderate electrical conductivity. The most common semiconductors are silicon, germanium, and gallium arsenide.


Rubber is a poor conductor of electricity. The chain polymer structure of rubber does not allow the free movement of electrons. Many electrical wire coatings are made from rubber for this exact reason. The rubber coating prevents the current from escaping the wiring and keeps the circuit intact. Additionally, electricians use thick rubber gloves to protect themselves from currents when working. As mentioned, the human body is an excellent conductor and will absorb electrical currents. Rubber gloves can protect electrical workers from dangerous, high-voltage currents on the job.

While pure rubber is a poor conductor, the right additives can alter the electrical conductivity of a rubber compound. Carbon or metallic additives, such as single-wall carbon nanotubes, can meaningfully increase the conductivity of a rubber material.


The atomic structure of metal allows for easy movement of free electrons between atoms. Because of this, most metals are excellent conductors of both heat and electricity. Silver is the most conductive metal on the planet, followed very closely by copper. Gold and aluminum also offer excellent conductivity. As with any material, each type of metal offers a blend of advantages and limitations. There are trade-offs to consider when choosing the best option for a given application.


The electrical conductivity of water is nuanced. Truly pure water—distilled and deionized water—is an excellent insulator and does not conduct electricity. This may be surprising to anyone who has been warned to stay away from water during a lightning storm. But pure water is virtually nonexistent in the natural world. That’s because water is an excellent solvent: Chemicals, minerals, and other substances will dissolve easily into water. If a body of water contains a conductive element, such as salt, then that body of water will conduct electricity.


In addition to being an excellent conductor of electricity, copper has many attractive properties that make it an extremely popular choice for electrical wiring. Copper is flexible, strong, and resistant to rust. Copper often takes on a greenish patina, called copper oxide. Copper oxide offers an extra layer of protection against corrosion and does not affect the conductivity of the material.

How Electricity Tests Are Performed

Electrical Testing Tools

A wide variety of electrical testing tools and instruments may be used to measure the electrical conductivity of a product, component, or circuit. Three common examples of electrical testers include the multimeter, the megohmmeter, and the low-resistance ohmmeter.

Multimeter (VOM)

A multimeter measures current, voltage, resistance, and other electrical properties simultaneously. Some varieties of multimeter are called volt-ohm-milliammeters (VOMs). Multimeters are ideal for capturing highly accurate, moment-in-time data for objective benchmarking purposes. Everyday consumers can purchase small, cheap multimeters at the hardware store or online, but these instruments do not offer the accuracy and precision of a laboratory-grade multimeter.


While a multimeter is used to measure currents, megohmmeters are used to measure insulation properties. A megohmmeter, also called a “megger,” is ideal for assessing the performance of insulation or coatings on wires, generators, and other components. A megohmmeter may be used to report the performance of a new insulation product or monitor for deterioration over time.

Low-Resistance Ohmmeter

Low-resistance ohmmeters, also called “ductor testers,” are used to test switches, circuits, bonds, and other connections for contact resistance. A variety of environmental conditions and other factors can cause conductivity problems between surfaces in contact. A low-resistance ohmmeter is an excellent tool for detecting and quantifying these issues quickly so a solution can be found.

Electrical Conductivity Test Standards

Many manufacturers and governing bodies require electrical components to comply with industry standards. These standards create a shared benchmark for quality and performance. Two of the most common electrical test standards for rubber insulation materials are ASTM D257 and ASTM D991.

ASTM D257: Standard Test Methods for DC Resistance or Conductance of Insulating Materials

ASTM D257 provides a standard test method for measuring the insulation resistance of an insulating material by exposing a sample of the material to 60 seconds of voltage. Both surface and volume resistivity of material can be observed using this method.

ASTM D991: Standard Test Method for Rubber Property—Volume Resistivity Of Electrically Conductive and Antistatic Products

While ASTM D257 measures for both surface and volume resistivity, ASTM D991 is specific to volume resistivity. ASTM D991 was designed for testing rubber materials and components that are used specific in anti-static products and electrically conductive products.

Electrical testing for rubber products from ACE Laboratories

The experts at ACE Laboratories have a deep understanding of rubber performance and conductivity properties. Whether you’re developing an insulating material or component or a conductive product, we can help you choose the right material and compound formulation to achieve your goals. We also offer top-quality laboratory testing so you can measure the efficacy and performance of every component before you go to market.

To learn more about electrical testing or discuss a project, get in touch with the experts at ACE >