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Mitchell Instrument Company and Fluke have been together for a VERY LONG time, we know these products like the back of our hand and they are almost always in stock. If you have any questions or need anything you cant find, please dont hesitate to give us a call or send us a message.

 

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What are Digital Multimeters?

Digital multimeters are the workhorses of the electronics industry. Almost all of the electronics industry. Almost all of the electronic products we use in our personal and professional lives are built or serviced using multimeters. Different DMM Digital multimeters applications require different degrees of attention to specs.

A technician checking a logic power supply can use his trusty bench DMM Digital multimeters confidently to verify that the supply is within a few percent of 5 V. However, when the job requires testing critical circuits, checking precision components, making fine adjustments in production, verifying compliance with industry standards, or taking measurements outside the controlled environment of the lab, then you'll need to evaluate specifications carefully.

A solid understanding of specifications is critical when you're evaluating the suitability of DMMs Digital multimeters for an application, or when you must be confident that your readings accurately reflects reality. This application note discusses some of the thinking behind DMM Digital multimeters specifications and specs sheets. It defines the various elements of DMM Digital Multimeters specs and gives tips on how to apply them.

Specifications and specs sheet

Whenever we take a measurement with any meter, we're gambling that the instrument is going to give us the "real" reading. Fortunately, its a very safe bet that a quality multimeter will deliver readings that coincide with reality. Specifications quantity the confidence of getting accurate readings and the risk of seeing inaccurate readings.

A specifications documents is a clearly written description of an instrument's performance. It should quantify an instrument's capabilities objectively under well-defined operating conditions.

From this formal definition we can draw the characteristics of good specifications:

• Completeness - any factor that impacts uncertainty is covered, including operating limits such as humidity, altitude, or vibration.
• Clarity - All efforts should be made to make the specifications straightforward
• Objectivity - Does not attempt to mislead for the sake of promotion

A well- written specification should maintain the same level of integrity as a medical chart or bank statement. Manufacturers must stand firmly behind their specs and you should fully expect that the information you are getting is accurate and complete.

On the specs sheet, you should see measurement uncertainty specs and modifiers that affect the uncertainty. You will also see operating limits that constrain the environment in which the uncertainty specifications will hold true. These are stated in numerical values (e.g humidity) or with reference to international standards (shock and vibration). First lets take a closer look at how we quantity measurement uncertainty.

Comparing different digital multimeters

When you are evaluating the suitability of several digital multimeters, the best approach is to choose a set of measurements and conditions that approximate your application. First, make sure the qualifiers of each DMM Digital Multimeters are compatible with the application environment. Then consider all of the functions (dc volts, ac volts, dc amps, ohms and so forth) and ranges you are likely to use. Are you going to be making a lot of measurements near the bottoms of ranges? Then make sure you compare with low readings to check the contribution of the floor. For each measurement, convert the uncertainty into measurement units like volts, ohms or amps. Compare the uncertainties in measurement units to decide which DMM Digital multimeters is better suited to the task at hand. The ability to work with DMM Digital multimeters uncertainty specifications is a fundamental engineering skill. When you get two different answers from two different DMMs Digital Multimeters, measurement uncertainty might explain the difference. When you need to compare the performance of DMM Digital Multimeters to decide the right tool for the job, being proficient with uncertainty specs will help you compare apples to apples. And whenever you are depending on an important measurement, you can be comfortable understanding hoe well your instrument will really perform.

How to evaluate a fluke digital multimeter's safety rating

If you faced with the task of replacing your multimeter, do one simple task before you start shopping: analyze the worst-case scenario of your job and determine what category your use or application fits into.

First choose a meter rated for the highest category you could be working in. Then, look for a multimeter with a voltage rating for that category matching your needs. While you're at it, don't forget the test leads. IEC 1010 applies to test leads too: they should be certified to a category and voltage as high or higher than the meter. When it comes to your personal protection, don't let test leads be the weak link.