Are you planning to buy a watt meter?

If your answer is in the affirmative, there are things you need to know before making your purchasing decision — like, its basic features and the different types of wattmeter available in the market.

For an outlander, a watt meter is an electric power measurement instrument used to measure Watts1 for any AC power circuit. There are hordes of wattmeters thronging the marketplace — from Heathkit, Collins, Swan, Drake, and Nye Viking — to MFJ, Diawa, Vectronics, Autek, Coaxial Dynamics, Palstar, Bird, and Kenwood. Almost all these manufacturers say theirs is accurate on frequency, while rendering the highest reading. What is the real story, let us find out. Types of Wattmeter Before narrowing down your choice of a standard wattmeter, you might want to explore the different types of wattmeter available in the market today.

1. Electrodynamics Wattmeter This wattmeter is one of the oldest and most frequently used to measure electric power in AC circuits. It consists of a pair of fixed or current coil, and a movable coil known as potential coil. The current coil is positioned in series, whereas, the potential coil or the movable coil is placed in parallel. Such an arrangement enables rotation of the potential coil by a limited angle, to an axis perpendicular to the fixed coils. Additionally, a needle is positioned in the wattmeter to indicate electric power.

2. Electricity meter is used to measure power at frequencies above the range of Electrodynamics Wattmeter. It is further divided into Vacuum Tube and Digital Wattmeter, depending upon the features and functions performed by the wattmeter.

3. Vacuum Tube Owing to its traditional design, this instrument can measure electric power in the nonlinear region of grid voltage and plate-current curves.

4. Digital Wattmeter This simple, yet optically isolated wattmeter is used to make accurate measurements of “real” power consumption, despite the presence of large reactive and DC components in the current drawn by the monitored load.

So there, now that you know about the different types of wattmeter, here are some tips to help your purchasing decision while buying a wattmeter from a trusted manufacturer.

If you are planning to buy a wattmeter from manufacturers like Coaxial Dynamics or Bird Electronic Corporation, it might be worthwhile to know that their “accuracy classification” claim of + or – 5% of full scale when the needle is mid-scale is correct.

If you want a measuring instrument that provides protection from the inverse attenuation effect, go for a cheap, cross-needle Putt-Putt wattmeter.

To measure the power of a single appliance or at a specific outlet, use the plug-in wattmeter. This instrument can be extensively used around your office or computer rooms, for testing the usefulness of an outlet and the power consumption of electronic items plugged into it. Plug-in wattmeters are able to detect damaged electronics or bad electrical wiring, by calculating the power flow through a single outlet. One of the simplest and easy-to-use wattmeter in this category includes the Kill-A-Watt EZ from the PowerMeterStore.

Professional-grade, portable wattmeters like the Test Equipment Depot and the Bird Model 5000-EX digital wattmeter fulfill the “on-site troubleshooting” needs of electricians, electrical repair crews, and system troubleshooters.

To stay on top of your electric bills, use digital wattmeters that evaluate the overall power consumption of an electrical system. These instruments have readouts that display where and how power is being consumed. Some advanced models even allow the power monitor to render small changes in the electrical power flow. Digital wattmeters like the Energy Detective and the EIG Shark 100 are quite a rage in the marketplace. The former is used to monitor a home office or small business, whereas the latter is used for more robust applications, such as large businesses or IT rooms.

Digital radio frequency (RF) wattmeters like Thomas Scherrer OZ2CPU are used to measure accurate RF power and gain in amplifiers, bandwidth in filters, transmitter power, Standing Wave Ratio (SWR), and return loss.

Some wattmeters like Palstar’s PM2000A have a dual movement meter system that measures and displays forward as well as reflected electric power.

Finally, whatever decision you make, please be reminded that wattmeters play an important role in the maintenance of large electrical systems. By measuring the overall wattage of a system, these instruments act as one of the first lines of defense versus electronic wear. Also, how you will use the instrument is an important consideration while deciding on the type of wattmeters you need.