DC Current Shunts

Using DC Current Shunts

A DC current shunt is a specialized resistor used to measure high currents. The shunt is wired in series with a heavy load, such as a DC motor, battery charger, heater, plating bath or smelter pot line. A DC voltmeter is connected to the shunt in a 4-wire (Kelvin) configuration. The shunt has bolt holes or


Insulation Testing: Megohmmeter or Hipot Tester

Insulation Testing: Megohmmeter or Hipot Tester

There are two common methods for performing insulation tests on cables, wiring and electrical equipment. One uses a megohmmeter to measure insulation resistance. The other uses a hipot tester to check for insulation breakdown. Both apply a high voltage, either ac or dc, to the device under test (DUT) and measure the resulting current flow. (more…)

AC Measurement

AC Measurement Considerations

Alternating current (ac) measurements involve more factors than direct current (dc) measurements. Let’s look at how some of these affect the measurement. We’ll focus on signals with a fundamental frequency below 1kHz. This is where digital multimeters and panel meters are typically used. Higher fundamental frequencies require instrumentation with wider bandwidth, such as audio meters or oscilloscopes. (more…)

Switchboard Thumbnail

What is a Switchboard Meter?

The National Electric Code (NFPA 70) defines a switchboard as ‘a large single panel, frame or assembly of panels on which are mounted… switches, overcurrent and other protective devices, buses, and instruments.’ A hundred years ago, the typical switchboard had knife switches, fuses, analog meters and other electrical apparatus mounted on a slate panel. It was large, heavy and live front, meaning hazardous voltages were exposed to the operator. (more…)

Panel Meter Selection Preview

Choosing the Right Panel Meter

Selecting a panel meter for a particular application can be a daunting task, given the wide variety of products that are available today. There are many factors to consider when making a decision. Let’s look at a few of the major items.