Being part of the Technical Support Team here at Extech I get a lot of frequently asked questions. There are a lot of meters available with a lot of functions built in these days. Often people are unsure what they need and will call in for a little guidance.
One of the more common questions I get is - "Should I purchase a Multimeter or a Clamp Meter?" "What are the advantages/disadvantages of one over the other?" Now, A lot of making this decision is personal preference and if you are in a specific trade then you may already know exactly what it is that you need and what specifications you need it to perform to.
When researching any type of instrument it is always good practice to refer to the published specifications from the back of instrument's User's Guide to make sure it will do what you need in terms of functions, ranges and resolution.
The main difference between the clamp meter and the multimeter, however, is the range of and way that they measure current. Most Multimeters measure current up to a range of 10 or 20 Amps Max(for short durations in seconds) and in order to make this measurement you need to break the cicuit and put the test leads in series to get the measurement. This may not be a problem if you are working with very small current draws or printed circuit boards etc., but if you are working in HVAC or any significant amount of current then it would benefit you to consider the Clamp Meter.
Extech offers all range types of clamps up to 1000Amps. The clamp allows you to simply clamp around a single conductor to make your measurement without having to break the circuit. It is the Hall Effect Sensor technology that it utilizes to do so. This is also a lot safer way of measuring current as you are non-contact and cannot damage the meter or yourself in the process. The Clamp Meter usually has the other functions that a multimeter has and comes with test leads. These measurments would be made through using the test leads just as you would with a multimeter. It is only the current that you are measuring by using the clamp on a single conductor. If you have no need to measure current then a multimeter may be the way to go.
This may have a finer resolution on functions like voltage and frequency and be more accurate say if you were a bench technician troubleshooting electonics to the component level or if you are just checking DC batteries and household devices for voltage. The choice is yours! Just make sure you do a little research so you get the right tool for the job and remember to always refer to the User Guides for Specifications on the meter being considered.
Extech's User Guides are all available online at http://www.extech.com/instruments/ I hope the information is helpful!