Voltmeter/Ammeter Switch

Instrumentation Switches Explained

An instrumentation switch (or instrument switch) is a special-purpose switch used in conjunction with an electrical meter in a control panel. It allows a single meter to read multiple circuits. The most common application is monitoring three-phase ac power systems. The meter is switched into the circuit to make a measurement. (more…)

Analog Multimeters

Advantages of An Analog Multimeter

The Simpson 260 has been an industry-standard multimeter for over 70 years. It is now available in 13 versions including industrial, ruggedized, safety rated, and high accuracy models. Why is this analog product still used, despite the abundance of digital multimeters? More generally, what advantages does an analog meter have compared to its digital counterpart? (more…)

AC Current Meters

AC Current Instrumentation

Last month’s posting covered the popular methods for sensing AC current (shunt, current transformer, Hall sensor, Rogowski coil). Here we will review some of the instruments available for fixed, portable, local and remote AC measurements. (more…)

AC Supply

AC Current Measurement Methods

There are two general methods for measuring ac currents:

  • by direct connection with the current-carrying circuit
  • by utilizing the magnetic field or flux generated by the current


Measurement Display

Display Resolution Is Not Accuracy

Casual users of digital instrumentation often assume that more resolution on the display provides a more accurate measurement – that an extra digit in the readout gives a decade improvement in accuracy. This is rarely the case. (more…)