Multimeter Buyers Guide
Selecting the Right Multimeter for Your RequirementsMultimeters are electronic devices that measure voltage, current and resistance. Although there are many different types of multimeters with different functions and benefits. Be it a small electronic connection or a large complicated circuit, every component ranging from a simple diode to a complex power amplifier needs to be tested for electrical properties.
A multimeter is an electronics designer's primary quality control tool. Making sure you have the right meter at the right price might take some planning. Some multimeters include additional specialized features or advanced options. Some technicians have specific requirements and may need a model targeted to meet their needs.
Analog MultimetersAnalog Multimeters, as you would suspect, use classic analog dials for measuring voltage, current and resistance. These are certainly more primitive and are rarely used these days, however some would argue that the analog meters are more sensitive than their digital counterparts and they are still preferred by many. After the slightest change in DC voltage, the needle on an analog multimeter can deflect, which affects the accuracy of measurement readings and might not be something you see on a digital meter. If you are dealing with circuits with highly sensitive measurements, an analog multimeter might be right for your needs.
Digital MultimetersDigital Multimeters (DMMs) consist of an LCD display, a knob to select ranges, an analog to digital converter and internal circuitry for signal conditioning. It is much more commonly used in today’s world and is primarily used to verify one of three factors of Ohm’s Law, voltage current and resistance.
Below is a simple equation used during diagnostic testing:
V = I x R
V = voltage
I = current
R = resistance
Digital multimeters are also used to verify the state of a circuit or system for safety purposed and to verify that a device is safe to work on. There are hundreds of models to choose from, so you need to filter down your options and consider various factors when selecting the correct DMM for you. Here are some things to keep in mind:
Digital Multimeter LCD Display
Multimeter PricesDMMs are available in a wide range of prices staring from $10 and going up to $1500. This depends on the brand and the included features. Higher priced meters tend to be more durable and accurate than the lower priced models. Workbench multimeters tend to be more expensive when compared to a Handheld DMM.
In general, we recommend looking at how frequently you will use the device and the features you need. If this is an occasional tool, a lower priced unit is probably fine. But, the more you plan to use the meter, the more you'll want a robust design and more expensive meter.
Multimeter Display CountsThe resolution of a meter, or display counts, is the smallest part of the scale which can be shown and is scale dependent. It refers to how large of a number the meter can display or the total digits that are displayed. The higher the display count, the better.
Versatility in Measurements and FunctionalityBasic multimeters have standard features such as measuring AC and DC current, voltages, resistance and capacitance. Other meters offer various tests (diode test, battery test, continuity test, transistor test) and special functions (auto range, analog bar graph, RS-232 PC interface, true RMS), which makes them more useful than a standard multimeter. Check out the device's user manual to review the functions offered and select your meter accordingly.
Multimeter SafetyWhen dealing with high voltages, it's very important to know which meter you should use. Based on the amount of current flowing through the conductor, you may want to choose a device that's a cross between a multimeter and a clamp meter.
Clamp MetersCreated as a single purpose test tool for electricians, the clamp meter is an electrical tester that combines a voltmeter with a clamp-type current meter. Clamp meters have an integrated transformer for the sole purpose of measuring current, which they can measure to the nearest tenth of a unit.
Unlike a multimeter, the clamp meter doesn't need to be connected to the circuit in order to measure current. All you need to do is place the clamp around a live wire to measure the current without interrupting the operation of the circuit. Clamp meters are ideal for electrical work as they can measure large AC currents.
Check the manufacturer's manual to see which models are suitable for which categories (CAT). The lower the CAT number, the lesser the protection.
Fluke Clamp Meter
- CAT I is for measurement of voltages from specially protected secondary circuits.
- CAT II refers to local level electrical distribution, such as from a standard wall outlet or plug in load.
- CAT III refers to measurements on hard-wired equipment in fixed installations, distribution boards and circuit breakers. The Fluke True-RMS Clamp Meter is suitable for a CAT III safety rating.
- CAT IV refers to the origin of installation or utility level measurements on primary over-current protection devices and on ripple control units. The Fluke 324 Clamp Meter is suitable for a CAT IV 300V safety rating.
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