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Application note: Core DMM functionality

Application note: Core DMM functionality
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Application note: Core DMM functionality - 1

Application Note Core handheld DMM functionality Handheld digital mutimeter is the most basic and the most widely used electrical instrument. From field electrician to service worker to a kid with their first broken toy, everyone tests their setup with one of these. Let us review their characteristics. One of the first actions an electrician or inspector should perform before doing any testing or measuring is visually checking the general state of facilities, with emphasis on electrical installations and systems and all metal or other conductors that could come into contact with individuals or animals. That usually includes machinery and appliance housings, pipes, valves, faucets, baths and similar objects. Besides looking for obvious signs of wear and tear and damage, especially that of electrical nature, attention should also be given to safe operation of connected electrical devices. Performance characteristics What makes the multimeter ‘better’ than the rest? For lab work or any precision task, it might easily be its performance. For field work, it would be presence of the commonly used feature, but even then, one need to be aware of the instrument’s limits. Resolution, counts, digits Being three ways to describe the same quality, these expressions only differ superficially. They all three mean the smallest change that the instrument can show. Resolution is usually given in units per range, e.g. 1 mV at 1V, which means that 1 mV is the smallest visible change when reading 1V value. Counts mean the largest number that can be displayed, which, combined with the chosen measuring range, means exactly the same as resolution. Digits are num

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Application note: Core DMM functionality - 2

of spaces for numbers on the screen. Most often it is decided that the first number or the most significant digit doesn’t have a full 0-9 range, but a smaller one, like only 0-1. Typical notation for that is 3 ½ digits. It means that three digits are full-range and one can only show 0 or 1, giving the display 1999 counts. However, some manufacturers use the ½ fraction for any narrowed range, not only 0-1, so by knowing the number of digits, number of counts is not yet clear. Accuracy Accuracy is the biggest error the instrument by itself would make under certain controlled conditions, or a...

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Application note: Core DMM functionality - 3

• CAT III 1000 V: working voltage 1000 V in building installations, meaning work on distribution boards, circuitbreakers, wiring, including cables, bus-bars, junction boxes, switches, socket-outlets in the fixed installation, and equipment for industrial. It can withstand a surge of 8 kV at 2 Ω source impedance or 4 kA. • CAT IV 600 V: working voltage 600 V at source of low-level instalations, like primary overcurrent protection devices and ripple control units. The specified surge protection is the same, 8 kV at 2 Ω source. Some multimeters are specified to CAT IV 1000 V, which can...

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Application note: Core DMM functionality - 4

Continuity is a check of connection between two points in the circuit. It is different from resistance in intent – one is not looking for exact resistance value, only that it is low enough. Most multimeters will give a beep when that happens, so that not even a look to the screen is needed. Diode test measures voltage drop over a silicone junction. It should read less than 0.7 V for forward direction and open circuit for reverse. If the instrument uses voltage lower than 0.6 V to measure resistance, it can be used to test resistors that would be normally isolated by silicone elements....

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Application note: Core DMM functionality 4Pages

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Application note: Core DMM functionality
4Pages