By Sean Silvey, product application specialist, Fluke
In the world of solar PV, a digital multimeter is a solar contractor’s most-used tool for troubleshooting, reviewing diagnostics and confirming repairs. With hundreds of options available, how do you know which digital multimeter is right for you? First, let’s review what exactly a digital multimeter is.
A digital multimeter is a test tool used to measure two or more electrical values — principally voltage, resistance and continuity. It is a standard diagnostic tool for technicians in the electrical/electronic industries.
Digital multimeters combine the testing capabilities of single-task meters — the voltmeter (for measuring volts), ammeter (amps) and ohmmeter (ohms). Often, they include several additional specialized features or advanced options. Technicians with special needs, like those in the solar industry, can seek out a model targeted to fit their needs.
Who needs a digital multimeter?
Digital multimeters are best suited for the installation and troubleshooting of combiner boxes and inverters, quick voltage detection and in environments with both AC and DC or ghost voltages.
Here’s a quick look at who needs one, and why.
Environment and safety
The increased occurrence and levels of transient over-voltages in today’s power systems have given rise to more stringent safety standards for electrical measurement equipment. Transients that ride on top of power sources (mains, feeder or branch circuits) can trigger a sequence of events that may lead to serious injury. Test equipment must be designed to protect people working in these high-voltage, high-current environments. Some things to consider when choosing testing equipment:
- The work environment (voltage level, types of equipment, types of measurements, applications)
- Specialty features/functions (capacitance, frequency, temperature, non-contact voltage, low impedance mode, min/max record, data logging, trending)
- Resolution and accuracy (6,000; 20,000; or 50,000 count resolution)
Measurement categories at a glance
To determine the correct overvoltage installation category rating (CAT II, CAT III, or CAT IV), it’s important to always choose the tool rated for the highest category it could be used in and select a voltage rating to match or exceed those situations. CAT-rated meters are designed to minimize or reduce the possibility of an arc flash occurring inside the meter. The ratings are usually located near the input jacks.
Each application with a digital multimeter presents potential safety hazards that must be considered when taking electrical measurements. Before using any electrical test equipment, people should always first refer to the user’s manual for proper operating procedures, safety precautions and limits.
Digital multimeter options
There are basically three types of digital multimeters with varying degrees of CAT ratings, safety features, resolution and accuracy. Here are the details about each option.
There are many factors that go into finding the right digital multimeter for the job. Choose carefully so the tool has a long lifespan of assessing solar projects.
Sean Silvey has been a product application specialist at Fluke for the past five years. Prior to that, he was a residential/commercial HVAC technician, and most recently a field service manager. Sean’s focus is on application awareness and product education.