Latest multimeters for measuring volts, amps and more

In any energy saving endeavour, the starting point is to understand the present state of energy consumption in terms of power consumed, V x I. Instantaneous measurement of voltage and current may be undertaken in order to understand which parts of a circuit, or which devices in an installation, are consuming the most energy. Today’s handheld digital multimeters can offer accurate voltage and current measurements in an inexpensive and portable format.

At the top end of the range of digital multimeters for industrial use is the Fluke 87V. This full-featured multimeter is designed for investigating complex signals; it can even make sense of noisy pulse-width modulation (PWM) signals, like those encountered when testing and diagnosing adjustable speed motor drives (ASDs). The 87V can accurately measure signals at the ASD (the readings may be compared with the information on the ASD display) and at the motor terminals. Accurate frequency measurements, and therefore motor speed, may be measured on ASDs using a specially designed low-pass filter. Special shielding protects the meter from high frequency noise that is typically generated by ASDs.

The 87V also features a special analogue display alongside its clear digital readout, which updates 40 times a second, 10 times faster than the digital readout. This is helpful when observing rapidly changing inputs and making peak and null adjustments. The segments below the digital readout light up to show the precise reading at that moment, and the scale changes as per the full-scale range selected.  Negative measurements are indicated by a lit-up minus sign. It’s also possible to zoom in on the analogue display using the meter’s zoom mode.

Other features of the Fluke 87V include capture of intermittent signals as fast as 250µs, a built-in thermometer, and a magnetic hanger for hands-free operation.

The Fluke 87V, specially designed for testing and diagnosing adjustable speed drives, features an analogue readout below the digital one which responds 10 times faster.

A new feature for digital multimeters is the ability to record measurements and display the saved data. As an example of this new breed of meters, the Metrix MTX3293 Recorder-Multimeter can store up to 6500 measurements in 10 sequences, and then display the measurements in the form of a graph (it has a graphical colour screen measuring 320 x 240 pixels for this purpose). This makes it very easy to spot trends in readings; the display can even be zoomed. Special SX-DMM software allows export of the data to a computer for further analysis, with communication via USB or Bluetooth. The readings can also be time and date stamped for convenience.

This meter can measure voltage up to 1000V and AC, DC or AC+DC current up to 10A. Frequency can be measured up to 5MHz, resistance up to 100MΩ and capacitance between 1nF and 60mF. The MTX3293 is also rugged for use either in the lab or in the field – it’s protected against dust and water to IP67 so can even be used outdoors. It’s a little bigger than most handheld meters but still perfectly portable.

The Metrix MTX3293 features a graphical display that can show traces – it can
store up to 6500 measurements in 10 sequences.

A more economical option, which still includes a recording function, might be the ISO-TECH IDM505. This compact multimeter features a memory to store and recall up to 1000 individual measurements. It also has a data log function which can capture successive measurements over a time period of 0.5 to 600 seconds; up to 20,000 measurements can be recorded using this function. The data can be exported to a computer using a USB cable and the software provided.

Specially designed for harsh environments, the IDM505 has a water-tight gasket and its rotary switch and input terminals are protected against dust and splashing. Its extra large 100,000/10,000 count digital display also shows a 43-segment analogue bar graph to provide a visual indicator of measurement trends.

The ISO-TECH IDM505 has a data log feature, which can capture up to 10 minutes’ worth of data (up to 20,000 measurements) for analysis.

And finally, at the budget end of the range, is the Keysight Technologies U1231A digital multimeter. This meter also has the ability to record and recall measurements, though as you’d expect, its memory isn’t as large as some of the other meters discussed here. The U1231A’s data log function can store 10 readings for recall, and the readings can be downloaded to a PC via an IR-to-USB cable. The U1231A also features an extremely practical LED torch on the back to illuminate the measurement area.

The Keysight Technologies U1231A offers a budget-friendly data log function which can store and recall up to 10 measurements.