Blu-ray Disc

Blu-ray Disc (BD) is a digital optical disc data storage format designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Conventional (pre-BD-XL) Blu-ray Discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives. The name Blu-ray Disc refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.

 The major application of Blu-ray Discs is as a medium for video material such as feature films. Besides the hardware specifications, Blu-ray Disc is associated with a set of multimedia formats. Generally, these formats allow for the video and audio to be stored with greater definition than on DVD.

The format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. Sony unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype player was released in April 2003 in Japan. Afterwards, it continued to be developed until its official release in June 2006. As of June 2008, more than 2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with 3,500 in the United States and Canada. In Japan, as of July 2010, more than 3,300 titles have been released.

During the high definition optical disc format war, Blu-ray Disc competed with the HD DVD format. Toshiba, the main company that supported HD DVD, conceded in February 2008, releasing its own Blu-ray Disc player in late 2009.

Media type	High-density optical disc
Encoding	H.262/MPEG-2 Part 2 H.264/MPEG-4 AVC VC-1
Capacity	25 GB (single-layer) 50 GB (dual-layer) 100/128 GB (BDXL)
Block size	64 KB ECC
Read mechanism	405 nm diode laser
Developed by	Blu-ray Disc Association
Dimensions	120 mm (4.7 in) diameter 1.2 mm thickness
Usage	Data storage High-definition video (1080p) High-definition audio Stereoscopic 3D PlayStation 3 games PlayStation 4 games Xbox One games

History

The information density of the DVD format was limited by the wavelength of the laser diodes used. Following protracted development, blue laser diodes operating at 405 nanometers became available on a production basis. Sony started two projects in collaboration with Philips applying the new diodes: UDO (Ultra Density Optical), and DVR Blue (together with Pioneer), a format of rewritable discs that would eventually become Blu-ray Disc (more specifically, BD-RE). The core technologies of the formats are similar.

The first DVR Blue prototypes were unveiled at the CEATEC exhibition in October 2000 by Sony. A trademark for the "Blue Disc" logo was filed February 9, 2001. On February 19, 2002, the project was officially announced as Blu-ray Disc, and Blu-ray Disc Founders was founded by the nine initial members.
The first consumer device arrived in stores on April 10, 2003: the Sony BDZ-S77, a $3,800 (US) BD-RE recorder that was made available only in Japan. But there was no standard for prerecorded video, and no movies were released for this player.

Hollywood studios insisted that players be equipped with digital rights management before they would release movies for the new format, and they wanted a new DRM system that would be more secure than the failed Content Scramble System (CSS) used on DVDs.

On October 4, 2004, the name "Blu-ray Disc Founders" was officially changed to the Blu-ray Disc Association (BDA), and 20th Century Fox joined the BDA's Board of Directors.
The Blu-ray Disc physical specifications were completed in 2004.

AACS LA, a consortium founded in 2004, had been developing the DRM platform that could be used to securely distribute movies to consumers. However, the final AACS standard was delayed,^[23] and then delayed again when an important member of the Blu-ray Disc group voiced concerns. At the request of the initial hardware manufacturers, including Toshiba, Pioneer, and Samsung, an interim standard was published that did not include some features, such as managed copy.

Competition from HD DVD

The DVD Forum, chaired by Toshiba, was split over whether to develop the more expensive blue laser technology. In March 2002, the forum approved a proposal endorsed by Warner Bros. and other motion picture studios that involved compressing HD content onto dual-layer standard DVD-9 discs. In spite of this decision, however, the DVD Forum's Steering Committee announced in April that it was pursuing its own blue-laser high-definition video solution. In August, Toshiba and NEC announced their competing standard, Advanced Optical Disc. It was finally adopted by the DVD Forum and renamed HD DVD the next year,after being voted down twice by DVD Forum members who were also Blu-ray Disc Association members—a situation that drew preliminary investigations by the U.S. Department of Justice.

HD DVD had a head start in the high-definition video market, as Blu-ray Disc sales were slow to gain market share. The first Blu-ray Disc player was perceived as expensive and buggy, and there were few titles available.
The appearance of the Sony PlayStation 3, which contained a Blu-ray Disc player for primary storage, helped support Blu-ray. Sony also ran a more thorough and influential marketing campaign for the format. 2006 also saw the launch of AVCHD camcorders, whose recordings can be played back on many Blu-ray Disc players without re-encoding, but not on HD DVD players.

By January 2007, Blu-ray Discs had outsold HD DVDs, and during the first three-quarters of 2007, BD outsold HD DVD by about two to one. At CES 2007, Warner proposed Total Hi Def—a hybrid disc containing Blu-ray on one side and HD DVD on the other, but it was never released.

Physical media

Laser and optics

While a DVD uses a 650 nm red laser, Blu-ray Disc uses a 405 nm "blue" laser diode. Note that even though the laser is called "blue", its color is actually in the violet range. The shorter wavelength can be focused to a smaller area, thus enabling it to read information recorded in pits that are less than half the size of those on a DVD, and can consequently be spaced more closely, resulting in a shorter track pitch, enabling a Blu-ray Disc to hold about five times the amount of information that can be stored on a DVD.
The lasers are GaN (gallium nitride) laser diodes that produce 405 nm light directly, that is, without frequency doubling or other nonlinear optical mechanisms. Conventional DVDs use 650 nm red lasers, and CDs use 780 nm near-infrared lasers.


The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85, and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused to a smaller spot, which effectively allows more information to be stored in the same area. For Blu-ray Disc, the spot size is 580 nm. This allows a reduction of the pit size from 400 nm for DVD to 150 nm for Blu-ray Disc, and of the track pitch from 740 nm to 320 nm. See Compact Disc for information on optical discs' physical structure.

In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding that further increase the amount of content that can be stored.

Hard-coating technology

Since the Blu-ray Disc data layer is closer to the surface of the disc compared to the DVD standard, it was at first more vulnerable to scratches. The first discs were housed in cartridges for protection, resembling Professional Discs introduced by Sony in 2003.

Using a cartridge would increase the price of an already expensive medium, so hard-coating of the pickup surface was chosen instead. TDK was the first company to develop a working scratch-protection coating for Blu-ray Discs. It was named Durabis. In addition, both Sony and Panasonic's replication methods include proprietary hard-coat technologies. Sony's rewritable media are spin-coated, using a scratch-resistant and antistatic coating. Verbatim's recordable and rewritable Blu-ray Discs use their own proprietary technology, called Hard Coat.
The Blu-ray Disc specification requires the testing of resistance to scratches by mechanical abrasion. In contrast, DVD media are not required to be scratch-resistant, but since development of the technology, some companies, such as Verbatim, implemented hard-coating for more expensive lineups of recordable DVDs.

Recording speed

If a USB 2.0 interface is used, the maximum drive speed is 8× (288 Mbit/s or 36 MB/s). A USB 3.0 interface (with proper cabling) does not have this limitation, and is capable of handling Blu-ray drive speeds far in excess of what is currently possible. The 5.25-inch (13.3 cm) width Blu-ray drives for desktop computer drive bays have a Serial ATA (SATA) interface. Even the oldest version of SATA has a transfer rate of 1.2 Gbit/s (150 MB/s), which is more than twice the demand of the 16× speed.
Note that interface speeds commonly advertise total throughput (for example, USB 2.0's 480 Mbit/s) that includes overhead such as the encoding scheme or error correction. Only the actual transfer speeds should be used to compare the interface with the drive speed.

Packaging

Prerecorded Blu-ray Disc titles usually ship in packages similar but slightly smaller (18.5 mm shorter and 1 mm thinner: 135 mm x 171.5 mm x 13 mm.) than a standard DVD keep case, generally with the format prominently displayed in a horizontal stripe across the top of the case (blue for Blu-ray, red for PlayStation 3 Greatest Hits Games, and clear for PlayStation 3 regular games). PlayStation 4 and Xbox One introduced new packaging for their games; unlike the PlayStation 3, PlayStation 4 now has blue cases much like the regular Blu-ray Disc cases, while Xbox One introduced a green case for their games.

Variants

Mini Blu-ray Disc

The "Mini Blu-ray Disc" (also, "Mini-BD" and "Mini Blu-ray") is a compact 8 cm (~3 in)-diameter variant of the Blu-ray Disc that can store approximately 7.8 GB of data. It is similar in concept to the MiniDVD and MiniCD. Recordable (BD-R) and rewritable (BD-RE) versions of Mini Blu-ray Disc have been developed specifically for compact camcorders and other compact recording devices.

Blu-ray Disc recordable

"Blu-ray Disc recordable" refers to two optical disc formats that can be recorded with an optical disc recorder. BD-Rs can be written to once, whereas BD-REs can be erased and re-recorded multiple times. The current practical maximum speed for Blu-ray Discs is about 12×. Higher speeds of rotation (10,000+ rpm) cause too much wobble for the discs to be written properly, as with the 20× and 52× maximum speeds, respectively, of standard DVDs and Cs.

Since September 2007, BD-RE is also available in the smaller 8 cm Mini Blu-ray Disc size.
On September 18, 2007, Pioneer and Mitsubishi codeveloped BD-R LTH ("Low to High" in groove recording), which features an organic dye recording layer that can be manufactured by modifying existing CD-R and DVD-R production equipment, significantly reducing manufacturing costs. In February 2008, Taiyo Yuden, Mitsubishi, and Maxell released the first BD-R LTH Discs, and in March 2008, Sony's PlayStation 3 gained official support for BD-R LTH Discs with the 2.20 firmware update. In May 2009 Verbatim/Mitsubishi announced the industry's first 6X BD-R LTH media, which allows recording a 25 GB disc in about 16 minutes.
Unlike the previous releases of 120 mm optical discs (i.e., CDs and standard DVDs), Blu-ray recorders hit the market almost simultaneously with Blu-ray's debut.

BD9 and BD5

The BD9 format was proposed to the Blu-ray Disc Association by Warner Home Video as a cost-effective alternative to the 25/50 GB BD-ROM discs. The format was supposed to use the same codecs and program structure as Blu-ray Disc video, but recorded onto less expensive 8.5 GB dual-layer DVD. This red-laser media could be manufactured on existing DVD production lines with lower costs of production than the 25/50 GB Blu-ray media.

Usage of BD9 for releasing content on "pressed" discs has never caught on. After the end of the format war, major producers ramped up the production of Blu-ray Discs and lowered their prices to the level of DVDs. On the other hand, the idea of using inexpensive DVD media became popular among individual users. A lower-capacity version of this format that uses single-layer 4.7 GB DVDs has been unofficially called BD5. Both formats are being used by individuals for recording high definition content in Blu-ray format onto recordable DVD media.

Despite the fact that the BD9 format has been adopted as part of the BD-ROM basic format, none of the existing Blu-ray player models support it explicitly. As such, the discs recorded in BD9 and BD5 formats are not guaranteed to play on standard Blu-ray Disc players.
AVCHD and AVCREC also use inexpensive media like DVDs, but unlike BD9 and BD5 these formats have limited interactivity, codec types, and data rates.
As of March 2011, BD9 was removed as an official BD-ROM disc.

BDXL

The BDXL format supports 100 GB and 128 GB write-once discs and 100 GB rewritable discs for commercial applications. It was defined in June 2010.

BD-R 3.0 Format Specification (BDXL) defined a multi-layered disc recordable in BDAV format with the speed of 2× and 4×, capable of 100/128 GB and usage of UDF2.5/2.6.

BD-RE 4.0 Format Specification (BDXL) defined a multi-layered disc rewritable in BDAV with the speed of 2× and 4×, capable of 100 GB and usage of UDF2.5 as file system.

IH-BD

The IH-BD (Intra-Hybrid Blu-ray) format includes a 25 GB re-writable layer (BD-RE) and a 25 GB write once layer (BD-ROM), designed to work with existing Blu-ray Discs.

Software standards

Filesystem

Blu-ray Disc specifies the use of Universal Disk Format (UDF) 2.50 as a convergent friendly format for both PC and consumer electronics environments. It is used in the latest specifications of BD-ROM, BD-RE and BD-R.
In the first BD-RE specification (defined in 2002), the BDFS (Blu-ray Disc File System) was used. The BD-RE 1.0 specification was defined mainly for the digital recording of High-definition television (HDTV) broadcast television. The BDFS was replaced by UDF 2.50 in the second BD-RE specification in 2005, in order to enable interoperability among consumer electronics Blu-ray recorders and personal computer systems. These optical disc recording technologies enabled PC recording and playback of BD-RE. BD-R can use UDF 2.50/2.60.
The Blu-ray Disc application (BDAV application) for recording of digital broadcasting has been developed as System Description Blu-ray Rewritable Disc Format part 3 Audio Visual Basic Specifications. The requirements related with computer file system have been specified in System Description Blu-ray Rewritable Disc Format part 2 File System Specifications version 1.0 (BDFS).

Initially, the BD-RE version 1.0 (BDFS) was specifically developed for recording of digital broadcasting using the Blu-ray Disc application (BDAV application). To support UDF, these requirements are superseded by the Blu-ray Rewritable Disc File System Specifications version 2.0 (UDF) (a.k.a. RE 2.0) and Blu-ray Recordable Disc File System Specifications version 1.0 (UDF) (a.k.a. R 1.0). Additionally, a new application format, BDMV (System Description Blu-ray Disc Prerecorded Format part 3 Audio Visual Basic Specifications) for High Definition Content Distribution was developed for BD-ROM. The only file system developed for BDMV is the System Description Blu-ray Read-Only Disc Format part 2 File System Specifications version 1.0 (UDF) which defines the requirements for UDF 2.50.

Media format

Container format

Audio, video and other streams are multiplexed and stored on Blu-ray Discs in a container format based on the MPEG transport stream. It is also known as BDAV MPEG-2 transport stream and can use filename extension .m2ts. Blu-ray Disc titles authored with menu support are in the BDMV (Blu-ray Disc Movie) format and contain audio, video, and other streams in BDAV container. There is also the BDAV (Blu-ray Disc Audio/Visual) format, the consumer oriented alternative to the BDMV format used for movie releases. The BDAV format is used on BD-REs and BD-Rs for audio/video recording. BDMV format was later defined also for BD-RE and BD-R (in September 2006, in the third revision of BD-RE specification and second revision of BD-R specification).

Blu-ray Disc employs the MPEG transport stream recording method. That enables transport streams of digital broadcasts to be recorded as they are broadcast, without altering the format. It also enables flexible editing of a digital broadcast that is recorded as is and where the data can be edited just by rewriting the playback stream. Although it is quite natural, a function for high-speed and easy-to use retrieval is built in. Blu-ray Disc Video use MPEG transport streams, compared to DVD's MPEG program streams. This allows multiple video programs to be stored in the same file so they can be played back simultaneously (e.g., with "picture-in-picture" effect).

Codecs

The BD-ROM specification mandates certain codec compatibilities for both hardware decoders (players) and movie software (content). Windows Media Player does not come with the codecs required to play Blu-ray discs.

Video

High-definition video may be stored on BD-ROMs with up to 1920×1080 pixel resolution at up to 60 (59.94) fields per second. Officially, progressive scan video can go up to 1920×1080 pixel resolution at 24 frames per second, or up to 59.94 frames per second at a resolution of 1280×720 pixels. Many current Blu-ray players and recorders now support 1920×1080 video at the full 60p and 50p progressive format.

For video, all players are required to support H.262/MPEG-2 Part 2, H.264/MPEG-4 Part 10: AVC, and SMPTE VC-1. BD-ROM titles with video must store video using one of the three mandatory formats; multiple formats on a single title are allowed. Blu-ray Disc supports video with a bit depth of 8-bits per color YCbCr with 4:2:0 chroma subsampling.

The choice of formats affects the producer's licensing/royalty costs as well as the title's maximum run time, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more-advanced video formats (VC-1 and MPEG-4 AVC) typically achieve a video run time twice that of MPEG-2, with comparable quality.

MPEG-2 was used by many studios (including Paramount Pictures, which initially used the VC-1 format for HD DVD releases) for the first series of Blu-ray Discs, which were launched throughout 2006. Modern releases are now often encoded in either MPEG-4 AVC or VC-1, allowing film studios to place all content on one disc, reducing costs and improving ease of use. Using these formats also frees a lot of space for storage of bonus content in HD (1080i/p), as opposed to the SD (480i/p) typically used for most titles. Some studios, such as Warner Bros., have released bonus content on discs encoded in a different format than the main feature title. For example, the Blu-ray Disc release of Superman Returns uses VC-1 for the feature film and MPEG-2 for some of its bonus content. Today, Warner and other studios typically provide bonus content in the video format that matches the feature.

Audio

For audio, BD-ROM players are required to support Dolby Digital (AC-3), DTS, and linear PCM. Players may optionally support Dolby Digital Plus and DTS-HD High Resolution Audio
as well as lossless formats Dolby TrueHD and DTS-HD Master Audio. BD-ROM titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs.

Bit rate

For users recording digital television programming, the recordable Blu-ray Disc standard's initial data rate of 36 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial). BD Video movies have a maximum data transfer rate of 54 Mbit/s, a maximum AV bitrate of 48 Mbit/s (for both audio and video data), and a maximum video bit rate of 40 Mbit/s. This compares to HD DVD movies, which have a maximum data transfer rate of 36 Mbit/s, a maximum AV bitrate of 30.24 Mbit/s, and a maximum video bitrate of 29.4 Mbit/s.

Application format

• BDAV or BD-AV (Blu-ray Disc Audio/Visual): a consumer-oriented Blu-ray video format used for audio/video recording (defined in 2002).
• BDMV or BD-MV (Blu-ray Disc Movie): a Blu-ray video format with menu support commonly used for movie releases.
• BDMV Recording specification (defined in September 2006 for BD-RE and BD-R).
• RREF (Realtime Recording and Editing Format): a subset of BDMV designed for realtime recording and editing applications.
• HFPA (High Fidelity Pure Audio): A high definition audio disc using the Blu-ray format

Java software support

Main article: BD-J

At the 2005 JavaOne trade show, it was announced that Sun Microsystems' Java cross-platform software environment would be included in all Blu-ray Disc players as a mandatory part of the standard. Java is used to implement interactive menus on Blu-ray Discs, as opposed to the method used on DVD-video discs. DVDs use pre-rendered MPEG segments and selectable subtitle pictures, which are considerably more primitive and rarely seamless. At the conference, Java creator James Gosling suggested that the inclusion of a Java virtual machine, as well as network connectivity in some BD devices, will allow updates to Blu-ray Discs via the Internet, adding content such as additional subtitle languages and promotional features not included on the disc at pressing time. This Java Version is called BD-J and is built on a profile of the Globally Executable MHP (GEM) standard; GEM is the worldwide version of the Multimedia Home Platform standard.

Player profiles

The BD-ROM specification defines four Blu-ray Disc player profiles, including an audio-only player profile (BD-Audio) that does not require video decoding or BD-J. All of the video-based player profiles (BD-Video) are required to have a full implementation of BD-J, with varying levels of hardware support.

On November 2, 2007, the Grace Period Profile was superseded by Bonus View as the minimum profile for new BD-Video players released to the market. When Blu-ray Disc software not authored with interactive features dependent on Bonus View or BD-Live hardware capabilities is played on Profile 1.0 players, it is able to play the main feature of the disc, but some extra features may not be available or will have limited capability.

BD-Live

The biggest difference between Bonus View and BD-Live is that BD-Live requires the Blu-ray Disc player to have an Internet connection to access Internet-based content. BD-Live features have included Internet chats, scheduled chats with the director, Internet games, downloadable featurettes, downloadable quizzes, and downloadable movie trailers. Note that while some Bonus View players may have an Ethernet port, these are used for firmware updates and are not used for Internet-based content. In addition, Profile 2.0 also requires more local storage in order to handle this content.


With the exception of the latest players and the PlayStation 3, Profile 1.0 players cannot be upgraded to be Bonus View or BD-Live compliant.

Backward compatibility

Though not compulsory, the Blu-ray Disc Association recommends that Blu-ray Disc drives be capable of reading standard DVDs and CDs, for backward compatibility. A few early Blu-ray Disc players released in 2006 could play DVDs but not CDs.

Variations

AVCHD

AVCHD was originally developed as a high definition format for consumer tapeless camcorders. Derived from the Blu-ray Disc specification, AVCHD shares a similar random access directory structure, but is restricted to lower audio and video bitrates, simpler interactivity, and the use of AVC-video and Dolby AC-3 (or linear PCM) audio.

Being primarily an acquisition format, AVCHD playback is not universally supported by all devices that support Blu-ray Disc playback. Nevertheless, many such devices are capable of playing AVCHD recordings from removable media, such as DVDs, SD/SDHC memory cards, "Memory Stick" cards, and hard disk drives.

AVCREC

AVCREC uses a BDAV container to record high definition content on conventional DVDs. Presently AVCREC is tightly integrated with the Japanese ISDB broadcast standard and is not marketed outside of Japan. AVCREC is used primarily in set-top digital video recorders and in this regard is comparable to HD REC.

Blu-ray 3D

The Blu-ray Disc Association (BDA) created a task force made up of executives from the film industry and the consumer electronics and IT sectors to help define standards for putting 3D film and 3D television content on a Blu-ray Disc. On December 17, 2009, the BDA officially announced 3D specs for Blu-ray Disc, allowing backward compatibility with current 2D Blu-ray players. The BDA has said, "The Blu-ray 3D specification calls for encoding 3D video using the "Stereo High" profile defined by Multiview Video Coding (MVC), an extension to the ITU-T H.264 Advanced Video Coding (AVC) codec currently supported by all Blu-ray Disc players. MPEG4-MVC compresses both left and right eye views with a typical 50% overhead compared to equivalent 2D content, and can provide full 1080p resolution backward compatibility with current 2D Blu-ray Disc players." This means the MVC (3D) stream is backward compatible with H.264/AVC (2D) stream, allowing older 2D devices and software to decode stereoscopic video streams, ignoring additional information for the second view.

Sony has released a firmware upgrade for PlayStation 3 consoles that enables 3D Blu-ray Disc playback. It previously released support for 3D gaming on April 21, 2010 (followed by the availability of 3D movies). Since the version 3.70 software update in August 9, 2011, the PlayStation 3 can support DTS-HD Master Audio and DTS-HD High Resolution Audio while playing 3D Blu-ray. Dolby TrueHD is used on a small minority of Blu-ray 3D releases, and bitstreaming is supported by slim PlayStation 3 models only (fat PS3 models decode internally and send audio as LPCM).

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Voltmeter

A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.
Voltmeters are made in a wide range of styles. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter, are standard test instruments used in electrical and electronics work. Any measurement that can be converted to a voltage can be displayed on a meter that is suitably calibrated; for example, pressure, temperature, flow or level in a chemical process plant.
General purpose analog voltmeters may have an accuracy of a few percent of full scale, and are used with voltages from a fraction of a volt to several thousand volts. Digital meters can be made with high accuracy, typically better than 1%. Specially calibrated test instruments have higher accuracies, with laboratory instruments capable of measuring to accuracies of a few parts per million. Meters using amplifiers can measure tiny voltages of microvolts or less.
Part of the problem of making an accurate voltmeter is that of calibration to check its accuracy. In laboratories, the Weston Cell is used as a standard voltage for precision work. Precision voltage references are available based on electronic circuits.

Analog voltmeter

A moving coil galvanometer can be used as a voltmeter by inserting a high-resistance resistor in series with the instrument. It employs a small coil of fine wire suspended in a strong magnetic field. When an electric current is applied, the galvanometer's indicator rotates and compresses a small spring. The angular rotation is proportional to the current through the coil. For use as a voltmeter, a series resistor is added so that the angular rotation becomes proportional to the applied voltage.
One of the design objectives of the instrument is to disturb the circuit as little as possible and so the instrument should draw a minimum of current to operate. This is achieved by using a sensitive galvanometer in series with a high resistance.
The sensitivity of such a meter can be expressed as "ohms per volt", the number of ohms resistance in the meter circuit divided by the full scale measured value. For example a meter with a sensitivity of 1000 ohms per volt would draw 1 milliampere at full scale voltage; if the full scale was 200 volts, the resistance at the instrument's terminals would be 200,000 ohms and at full scale the meter would draw 1 milliampere from the circuit under test. For multi-range instruments, the input resistance varies as the instrument is switched to different ranges.
Moving-coil instruments with a permanent-magnet field respond only to direct current. Measurement of AC voltage requires a rectifier in the circuit so that the coil deflects in only one direction. Moving-coil instruments are also made with the zero position in the middle of the scale instead of at one end; these are useful if the voltage reverses its polarity.
Voltmeters operating on the electrostatic principle use the mutual repulsion between two charged plates to deflect a pointer attached to a spring. Meters of this type draw negligible current but are sensitive to voltages over about 100 volts and work with either alternating or direct current.

VTVMs and FET-VMs

The sensitivity and input resistance of a voltmeter can be increased if the current required to deflect the meter pointer is supplied by an amplifier and power supply instead of by the circuit under test. The electronic amplifier between input and meter gives two benefits; a rugged moving coil instrument can be used, since its sensitivity need not be high, and the input resistance can be made high, reducing the current drawn from the circuit under test. Amplified voltmeters often have an input resistance of 1, 10, or 20 megohms which is independent of the range selected. A once-popular form of this instrument used a vacuum tube in the amplifier circuit and so was called the vacuum tube voltmeter, or VTVM. These were almost always powered by the local AC line current and so were not particularly portable. Today these circuits use a solid-state amplifier using field-effect transistors, hence FET-VM, and appear in handheld digital multimeters as well as in bench and laboratory instruments. These are now so ubiquitous that they have largely replaced non-amplified multimeters except in the least expensive price ranges.
Most VTVMs and FET-VMs handle DC voltage, AC voltage, and resistance measurements; modern FET-VMs add current measurements and often other functions as well. A specialized form of the VTVM or FET-VM is the AC voltmeter. These instruments are optimized for measuring AC voltage. They have much wider bandwidth and better sensitivity than a typical multifunction device.

Digital voltmeter

The first digital voltmeter was invented and produced by Andrew Kay of Non-Linear Systems (and later founder of Kaypro) in 1954.
Digital voltmeters (DVMs) are usually designed around a special type of analog-to-digital converter called an integrating converter. Voltmeter accuracy is affected by many factors, including temperature and supply voltage variations. To ensure that a digital voltmeter's reading is within the manufacturer's specified tolerances, they should be periodically calibrated against a voltage standard such as the Weston cell.
Digital voltmeters necessarily have input amplifiers, and, like vacuum tube voltmeters, generally have a constant input resistance of 10 megohms regardless of set measurement range.

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Multimeter

A multimeter or a multitester, also known as a VOM (Volt-Ohm meter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter would include basic features such as the ability to measure voltage, current and resistance. Analog multimeters use a microammeter whose pointer moves over a scale calibrated for all the different measurements that can be made. Digital multimeters (DMM, DVOM) display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured. Digital multimeters are now far more common than analog ones, but analog multimeters are still preferable in some cases, for example when monitoring a rapidly-varying value.
A multimeter can be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as electronic equipment, motor controls, domestic appliances, power supplies, and wiring systems.

History

The first moving-pointer current-detecting device was the galvanometer in 1820. These were used to measure resistance and voltage by using a Wheatstone bridge, and comparing the unknown quantity to a reference voltage or resistance. While useful in the lab, the devices were very slow and impractical in the field. These galvanometers were bulky and delicate.
The D'Arsonval/Weston meter movement used a fine metal spring to give proportional measurement rather than just detection, and built-in permanent field magnets made deflection independent of the orientation of the meter. Instead of balancing a bridge, values could be directly read off the instruments's scale, which made measurement quick and easy. By adding a series or shunt resistor, more than one range of voltage or current could be measured with one movement.
Multimeters were invented in the early 1920s as radio receivers and other vacuum tube electronic devices became more common. The invention of the first multimeter is attributed to British Post Office engineer, Donald Macadie, who became dissatisfied with having to carry many separate instruments required for the maintenance of the telecommunications circuits. Macadie invented an instrument which could measure amperes ( amps), volts and ohms, so the multifunctional meter was then named Avometer. The meter comprised a moving coil meter, voltage and precision resistors, and switches and sockets to select the range.
Additional scales such as decibels, and measurement functions such as capacitance, transistor gain, frequency, duty cycle, display hold, and buzzers which sound when the measured resistance is small have been included on many multimeters. While multimeters may be supplemented by more specialized equipment in a technician's toolkit, some multimeters include additional functions for specialized applications (temperature with a thermocouple probe, inductance, connectivity to a computer, speaking measured value, etc.).

Operation

A multimeter is a combination of a multirange DC voltmeter, multirange AC voltmeter, multirange ammeter, and multirange ohmmeter. An un-amplified analog multimeter combines a meter movement, range resistors and switches.
For an analog meter movement, DC voltage is measured with a series resistor connected between the meter movement and the circuit under test. A set of switches allows greater resistance to be inserted for higher voltage ranges. The product of the basic full-scale deflection current of the movement, and the sum of the series resistance and the movement's own resistance, gives the full-scale voltage of the range. As an example, a meter movement that required 1 milliampere for full scale deflection, with an internal resistance of 500 ohms, would, on a 10-volt range of the multimeter, have 9,500 ohms of series resistance.
For analog current ranges, low-resistance shunts are connected in parallel with the meter movement to divert most of the current around the coil. Again for the case of a hypothetical 1 mA, 500 ohm movement on a 1 Ampere range, the shunt resistance would be just over 0.5 ohms.
Moving coil instruments respond only to the average value of the current through them. To measure alternating current, a rectifier diode is inserted in the circuit so that the average value of current is non-zero. Since the rectified average value and the root-mean-square value of a waveform need not be the same, simple rectifier-type circuits may only be accurate for sinusoidal waveforms. Other wave shapes require a different calibration factor to relate RMS and average value. Since practical rectifiers have non-zero voltage drop, accuracy and sensitivity is poor at low values.
To measure resistance, a small battery within the instrument passes a current through the device under test and the meter coil. Since the current available depends on the state of charge of the battery, a multimeter usually has an adjustment for the ohms scale to zero it. In the usual circuit found in analog multimeters, the meter deflection is inversely proportional to the resistance; so full-scale is 0 ohms, and high resistance corresponds to smaller deflections. The ohms scale is compressed, so resolution is better at lower resistance values.
Amplified instruments simplify the design of the series and shunt resistor networks. The internal resistance of the coil is decoupled from the selection of the series and shunt range resistors; the series network becomes a voltage divider. Where AC measurements are required, the rectifier can be placed after the amplifier stage, improving precision at low range.
Digital instruments, which necessarily incorporate amplifiers, use the same principles as analog instruments for range resistors. For resistance measurements, usually a small constant current is passed through the device under test and the digital multimeter reads the resultant voltage drop; this eliminates the scale compression found in analog meters, but requires a source of significant current. An autoranging digital multimeter can automatically adjust the scaling network so that the measurement uses the full precision of the A/D converter.
In all types of multimeters, the quality of the switching elements is critical to stable and accurate measurements. Stability of the resistors is a limiting factor in the long-term accuracy and precision of the instrument.

Quantities measured

Contemporary multimeters can measure many quantities. The common ones are:

• Voltage, alternating and direct, in volts.
• Current, alternating and direct, in amperes.
  The frequency range for which AC measurements are accurate must be specified.
• Resistance in ohms.

Additionally, some multimeters measure:

• Capacitance in farads.
• Conductance in siemens.
• Decibels.
• Duty cycle as a percentage.
• Frequency in hertz.
• Inductance in henrys.
• Temperature in degrees Celsius or Fahrenheit, with an appropriate temperature test probe, often a thermocouple.

Digital multimeters may also include circuits for:

• Continuity tester; sounds when a circuit conducts
• Diodes (measuring forward drop of diode junctions), and transistors (measuring current gain and other parameters)
• Battery checking for simple 1.5 volt and 9 volt batteries. This is a current loaded voltage scale which simulates in-use voltage measurement.

Various sensors can be attached to multimeters to take measurements such as:

• Light level
• Acidity/Alkalinity(pH)
• Wind speed
• Relative humidity

Accuracy

Digital multimeters generally take measurements with accuracy superior to their analog counterparts. Standard analog multimeters measure with typically ±3% accuracy, though instruments of higher accuracy are made. Standard portable digital multimeters are specified to have an accuracy of typically 0.5% on the DC voltage ranges. Mainstream bench-top multimeters are available with specified accuracy of better than ±0.01%. Laboratory grade instruments can have accuracies of a few parts per million.
Accuracy figures need to be interpreted with care. The accuracy of an analog instrument usually refers to full-scale deflection; a measurement of 30V on the 100V scale of a 3% meter is subject to an error of 3V, 10% of the reading. Digital meters usually specify accuracy as a percentage of reading plus a percentage of full-scale value, sometimes expressed in counts rather than percentage terms.
Quoted accuracy is specified as being that of the lower millivolt (mV) DC range, and is known as the "basic DC volts accuracy" figure. Higher DC voltage ranges, current, resistance, AC and other ranges will usually have a lower accuracy than the basic DC volts figure. AC measurements only meet specified accuracy within a specified range of frequencies.
Manufacturers can provide calibration services so that new meters may be purchased with a certificate of calibration indicating the meter has been adjusted to standards traceable to, for example, the US National Institute of Standards and Technology (NIST), or other national standards organization.
Test equipment tends to drift out of calibration over time, and the specified accuracy cannot be relied upon indefinitely. For more expensive equipment, manufacturers and third parties provide calibration services so that older equipment may be recalibrated and recertified. The cost of such services is disproportionate for inexpensive equipment; however extreme accuracy is not required for most routine testing. Multimeters used for critical measurements may be part of a metrology program to assure calibration.
A multimeter can be assumed to be "average responding" to AC waveforms unless stated as being a "True RMS" type. An average responding mulimeter will only meet its specified accuracy on AC volts and amps for purely sinusoidal waveforms. A True RMS responding multimeter on the other hand will meet its specified accuracy on AC volts and current with any waveform type up to a specified crest factor.
A meter's AC voltage and current accuracy may have different specifications for different ranges of frequency.

Digital multimeters (DMM or DVOM)

Modern multimeters are often digital due to their accuracy, durability and extra features. In a digital multimeter the signal under test is converted to a voltage and an amplifier with electronically controlled gain preconditions the signal. A digital multimeter displays the quantity measured as a number, which eliminates parallax errors.
Modern digital multimeters may have an embedded computer, which provides a wealth of convenience features. Measurement enhancements available include:

• Auto-ranging, which selects the correct range for the quantity under test so that the most significant digits are shown. For example, a four-digit multimeter would automatically select an appropriate range to display 1.234 instead of 0.012, or overloading. Auto-ranging meters usually include a facility to hold the meter to a particular range, because a measurement that causes frequent range changes can be distracting to the user. Other factors being equal, an auto-ranging meter will have more circuitry than an equivalent non-auto-ranging meter, and so will be more costly, but will be more convenient to use.
• Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads).
• Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.
• Current-limited tests for voltage drop across semiconductor junctions. While not a replacement for a transistor tester, this facilitates testing diodes and a variety of transistor types.
• A graphic representation of the quantity under test, as a bar graph. This makes go/no-go testing easy, and also allows spotting of fast-moving trends.
• A low-bandwidth oscilloscope.
• Automotive circuit testers, including tests for automotive timing and dwell signals.
• Simple data acquisition features to record maximum and minimum readings over a given period, or to take a number of samples at fixed intervals.
• Integration with tweezers for surface-mount technology.
• A combined LCR meter for small-size SMD and through-hole components.

Modern meters may be interfaced with a personal computer by IrDA links, RS-232 connections, USB, or an instrument bus such as IEEE-488. The interface allows the computer to record measurements as they are made. Some DMMs can store measurements and upload them to a computer.
The first digital multimeter was manufactured in 1955 by Non Linear Systems.

Probes

A multimeter can utilize a variety of test probes to connect to the circuit or device under test. Crocodile clips, retractable hook clips, and pointed probes are the three most common attachments. Tweezer probes are used for closely spaced test points, as in surface-mount devices. The connectors are attached to flexible, thickly insulated leads that are terminated with connectors appropriate for the meter. Probes are connected to portable meters typically by shrouded or recessed banana jacks, while benchtop meters may use banana jacks or BNC connectors. 2mm plugs and binding posts have also been used at times, but are less common today.

Clamp meters clamp around a conductor carrying a current to measure without the need to connect the meter in series with the circuit, or make metallic contact at all. Types to measure AC current use the transformer principle; clamp-on meters to measure small current or direct current require more complicated sensors.

Power Supply

Analog meters can measure voltage and current using power from the test circuit but require internal power for resistance testing, electronic meters always require an internal power supply. Hand-held meters use batteries while bench meters usually use mains power allowing the meter to test devices not connected to a circuit. Such testing requires that the component be isolated from the circuit as otherwise other current paths will most likely distort measurements.

Meters intended for testing in hazardous locations or for use on blasting circuits may require use of a manufacturer-specified battery to maintain their safety rating.

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Seven Segment Digital Clock Circuit Using MM5314

Seven Segment Digital Clock Circuit Using MM5314

Overview

The circuit has been designed to create a digital clock using a single IC MM5314N with all the functions provided in the operation.

Terminology

• MM5314 – a monolithic MOS integrated circuit that utilizes P-channel low threshold, enhancement mode and ion planted, depletion mode devices which has features such as internal multiplex oscillator, fast and slow set controls, single power supply, 7-segment outputs, leading zero blanking, operating at 50 Hz or 60 Hz, and 12 or 24 hour display format
• 7 Segment LED – is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot-matrix displays also known as seven-segment indicator

Circuit Explanation

A digital clock is a type of clock in which the time is displayed in a numerical form being associated with electronic devices. It uses a digital display rather than moving hands. The basis of the circuit design evolves in a single MOS IC MM5314N. Other necessary circuits are operated through the MM5314 IC which works together with six common anode 7-segment displays. The multisegment LED common anode configuration reduces the number of wires between the LED modules where all positive ends are connected together. In practical design, the longest pin of the LED is the positive or the anode part.

The 7-segment displays are driven by thirteen transistors consisting of BC550 and BC560. The timing of the circuit is determined by the frequency of the network with a value of 50 Hz, which imposes the simplest solution. To maintain a stable output frequency, a crystal oscillator may be used. It uses a quartz crystal to produce fixed frequency oscillations where accuracy and stability are the primary considerations. It uses the mechanical resonance of a vibrating crystal to produce a very precise frequency from the creation of an electrical signal.

The six displays of 7-segment common anode provide the output for the time. LEDs DS1 and DS2 represent the Hour, LEDs DS3 and DS4 represent the Minutes, and LEDs DS5 and DS6 represent the Seconds.  The collector of transistors Q8 to Q13 powers the common anode of each display. Each display consists of individual LEDs a, b, c, d, e, f, & g, are linked in parallel combination, which are then driven by the transistors Q1 to Q7. This type of connection creates a multiplexing system with a frequency of 1 KHz that is controlled by the RC circuit R3 and C3. The power supply contains the typical circuit having a bridge rectifier across the secondary coil with a parallel capacitor across the bridge. The resistor R2 and capacitors C2 to C5 handles the separation and limiting of voltage to protect the integrated circuit from surge and peak voltages.

The rectified vibrations in pin 16 are limited by the diode D1 while resistors R18 to R24 are limiting the excess current from the LED. The use of switch S1, if put in position 1, is to adjust the clock to the required time and display. It will remain open unless it is switched to the other position which causes the display to be in a fixed value and save the settings, resuming the operation of the clock. In this scenario, the clock may be placed with a tolerable distance to avoid the effect of light from the LED display. Switch S2 on the other hand is responsible for adjusting the clock to operate on a 12-hour or 24-hour basis by changing the positions of the contacts. The adjustments of seconds are made possible when switch S3 is in position 1. The setting for the seconds is saved when the contact is changed to position 2. During an interruption in the operation of the clock, switches S3, S4, and S5 can be used for alterations. These are push-to-make switches which return to its normally open or OFF position upon releasing the button, like the standard doorbell switch.

The frequency of the main voltage around 50 Hz or 60 Hz is fed into pin 11 which is connected to pin 2 if the main voltage is 110 VAC at 60 Hz. Otherwise, pin 11 will not be connected anywhere if the main voltage is 220 VAC at 50 Hz. Pin 16 handles the incoming 50 Hz or 60 Hz at the input with the sample from the main voltage. The counter circuits are triggered by the sample function which becomes the adjustment of time. Having 110 V causes the pin 11 to connect Vss at pin 2 while having a 220 V nulls the function of pin 11.

Part List

R1= 100Kohms R2= 47Kohms R3= 100Kohms R4.....10= 2.2Kohms R11.....17= 10Kohms R18.....24-25-26= 220 ohms  0W5 R25-26=1.2Kohms  0W5

C1= 2200uF 25V C2= 100uF 25V C3= 18nF 100V polyester C4-5= 10nF ceramic OR polyester Q1....7= BC550 Q8....13= BC560 IC1= MM5314N

D1= 1N4148 GR1= 4X1N4002 S1...3= 1X2 mini switch S4...6= Push Button normal open T1= 220V AC/12V 1A DS1....DS7= 7 Seg. Disp. Common Anode

Application

Digital clocks are widely used as desk clocks, interval timers, industrial clocks, or automobile clocks. They can also be utilized in cell phones, computers, microwave ovens, televisions, and radios, since digital clocks are inexpensive and very small devices, which make them more popular in the designs. The LED digital clocks are also used as digital electronic time zone displays used in governments and companies with more than one office across the country or around the world. Schools, universities, and hospitals are using wireless clocks as the desired method for providing synchronized clocks without the need to lay sync wire.

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