Wednesday, June 29, 2011
A Guide to Understanding Multimeters
A multimeter is a device used as an electronic measuring instrument. It is capable of performing a varied number of measurement functions. Multimeters are also known as multitesters or Volt-Ohm meters (VOMs). Hand-held models of the instrument are available for those working in the field and a bench instrument version is also available for more accurate readings. The instrument’s basic function is to help troubleshoot electrical and electronic problems in the electronic devices such as large-scale electronic equipments, domestic appliances, wiring systems, motor controls and power supplies.
Despite being available in various brands and styles, every multimeter is sure to offer the same basic functionalities. A multimeter is so named because it can perform functions that are normally done by a single instrument. When used in the voltmeter mode, it can measure the amount of voltage running through any given circuit. This voltage reading can then be compared to the expected or ideal voltage specified for the circuit. It can also be used as an ammeter to measure the amount of current passing through a certain circuit. In addition to these functions, it can also work like an ohmmeter. In this mode, the meter will be able to read the inherent resistance of a circuit from its power output. More advanced models can measure inductance, frequency, capacitance and temperature. Some can even test transistors and diodes.
A typical multimeter consists of a display, probes, terminals and a dial to set the different measurement ranges. Depending on the type, the display can either be a numeric digital one or a dial display. The probes of a multimeter are used to connect the instrument to the device or circuit under scrutiny. The most common attachments in use are crocodile clips, pointed probes and retractable clips. The terminals inside it are connected to resistors corresponding to the range selected.
There are two main types of multimeters in the market- digital and analogue. An analogue multimeter moves a needle along a scale shown on the display panel of the device. Measurement is done by judging the needle’s position on the dial. This may sometimes result in inaccuracies in the measurements taken because readings can oftentimes become subjective. However, analog meters can display the changes in reading through time. They are often useful in instances when the person taking the measurements needs to focus on other tasks as well. The range of this type of device is known as the Full Scale Deflection (FSD) or the maximum range that the instrument can read. It is also useful in taking readings that are beyond a typical multimeter’s range. For this purpose, the probes of the meter are usually made to touch the circuit and the speed of the movement of the needle toward the meter’s FSD is noted.
Digital multimeters on the other hand are popular for their accuracy and precision. Unlike its analogue counterpart, digital meters give measurements that can be read directly on the display panel. In addition to that, modern digital meters can also provide additional features. Some digital meters for example can automatically select the right range for the circuit under inspection. It can also give correct readings even if the probes are connected to the circuit in reverse. Typical digital meters cannot, however, give the trends or changes that a reading may undergo through time. They also cannot be made to take readings that are higher than their specified range.
Each type of multimeter has its own advantages and disadvantages. When used to take voltage readings, an analogue meter is usually a better choice because it has a much higher resistance when compared to a digital reader with a similar range. In addition to that, it is typically easier for an observer to follow slow changes in voltage when using an analogue meter rather than a digital one. When used to measure current, an analogue meter usually takes good readings because of its high sensitivity. Recent advances in technology however have made it possible for digital meters to perform as well as or even better than typical analogue meters.
Like all other devices, safe operation still must be observed when handling multimeters. There are a number of safety practices recommended for users to ensure that no harm and accidents occur during use of the instrument. The simplest way to go about this is to ensure that the meter selected matches the voltage levels of the circuit, device or installation meant to be tested. Doing so not only prevents the possibility of a damaged an unusable meter but it also ensures personal safety especially on the part of the one doing the measurements. Most models have fuse or fuses pre-installed in the device to prevent damage but no risks should be taken as some fuses don’t work as expected at times.
Multimeters are rated into categories based on their intended use. A higher category number would indicate that the meter is more resistant to higher energy transients. Thus a meter with a higher rating is expected to withstand higher energies as compared to lower rated ones. There are four categories given to multimeters.
The first, or Category I, refers to meters used to test electronics or equipments that are not directly connected to the main power source. Category II meters are used on single phase sub-circuits or on appliances and household loads. Meters under Category III are used on equipments that are permanently installed such as motors and distribution panels. Commercial lighting applications, three-phase appliance outlets and small industrial installations are also tested using Category III meters. The last category, Category IV, is for meters used for testing commercial and residential main feeds, power lines and overcurrent protection equipments. Caution should be observed to make sure that the proper meters are utilized properly based on their intended purposes.
These are just some of the facts about multimeters. Being familiar with these bits of knowledge will help one better understand the workings of this nifty device. Specific methods of handling this instrument will vary from manufacturer to manufacturer but the important thing to remember is to always be cautious during operation of any multimeter.
Despite being available in various brands and styles, every multimeter is sure to offer the same basic functionalities. A multimeter is so named because it can perform functions that are normally done by a single instrument. When used in the voltmeter mode, it can measure the amount of voltage running through any given circuit. This voltage reading can then be compared to the expected or ideal voltage specified for the circuit. It can also be used as an ammeter to measure the amount of current passing through a certain circuit. In addition to these functions, it can also work like an ohmmeter. In this mode, the meter will be able to read the inherent resistance of a circuit from its power output. More advanced models can measure inductance, frequency, capacitance and temperature. Some can even test transistors and diodes.
A typical multimeter consists of a display, probes, terminals and a dial to set the different measurement ranges. Depending on the type, the display can either be a numeric digital one or a dial display. The probes of a multimeter are used to connect the instrument to the device or circuit under scrutiny. The most common attachments in use are crocodile clips, pointed probes and retractable clips. The terminals inside it are connected to resistors corresponding to the range selected.
There are two main types of multimeters in the market- digital and analogue. An analogue multimeter moves a needle along a scale shown on the display panel of the device. Measurement is done by judging the needle’s position on the dial. This may sometimes result in inaccuracies in the measurements taken because readings can oftentimes become subjective. However, analog meters can display the changes in reading through time. They are often useful in instances when the person taking the measurements needs to focus on other tasks as well. The range of this type of device is known as the Full Scale Deflection (FSD) or the maximum range that the instrument can read. It is also useful in taking readings that are beyond a typical multimeter’s range. For this purpose, the probes of the meter are usually made to touch the circuit and the speed of the movement of the needle toward the meter’s FSD is noted.
Digital multimeters on the other hand are popular for their accuracy and precision. Unlike its analogue counterpart, digital meters give measurements that can be read directly on the display panel. In addition to that, modern digital meters can also provide additional features. Some digital meters for example can automatically select the right range for the circuit under inspection. It can also give correct readings even if the probes are connected to the circuit in reverse. Typical digital meters cannot, however, give the trends or changes that a reading may undergo through time. They also cannot be made to take readings that are higher than their specified range.
Each type of multimeter has its own advantages and disadvantages. When used to take voltage readings, an analogue meter is usually a better choice because it has a much higher resistance when compared to a digital reader with a similar range. In addition to that, it is typically easier for an observer to follow slow changes in voltage when using an analogue meter rather than a digital one. When used to measure current, an analogue meter usually takes good readings because of its high sensitivity. Recent advances in technology however have made it possible for digital meters to perform as well as or even better than typical analogue meters.
Like all other devices, safe operation still must be observed when handling multimeters. There are a number of safety practices recommended for users to ensure that no harm and accidents occur during use of the instrument. The simplest way to go about this is to ensure that the meter selected matches the voltage levels of the circuit, device or installation meant to be tested. Doing so not only prevents the possibility of a damaged an unusable meter but it also ensures personal safety especially on the part of the one doing the measurements. Most models have fuse or fuses pre-installed in the device to prevent damage but no risks should be taken as some fuses don’t work as expected at times.
Multimeters are rated into categories based on their intended use. A higher category number would indicate that the meter is more resistant to higher energy transients. Thus a meter with a higher rating is expected to withstand higher energies as compared to lower rated ones. There are four categories given to multimeters.
The first, or Category I, refers to meters used to test electronics or equipments that are not directly connected to the main power source. Category II meters are used on single phase sub-circuits or on appliances and household loads. Meters under Category III are used on equipments that are permanently installed such as motors and distribution panels. Commercial lighting applications, three-phase appliance outlets and small industrial installations are also tested using Category III meters. The last category, Category IV, is for meters used for testing commercial and residential main feeds, power lines and overcurrent protection equipments. Caution should be observed to make sure that the proper meters are utilized properly based on their intended purposes.
These are just some of the facts about multimeters. Being familiar with these bits of knowledge will help one better understand the workings of this nifty device. Specific methods of handling this instrument will vary from manufacturer to manufacturer but the important thing to remember is to always be cautious during operation of any multimeter.
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