ac bias การใช้

• High frequency AC bias was used to linearize the recording.
• The original patent for AC bias was filed by W . L . Carlson and Glenn L . Carpenter in 1921, eventually resulting in.
• These included both the newer oxide coated PVC tape developed by I . G . Farben ( BASF division ) as well as the AC bias system.
• The value of AC bias was somewhat masked by the primitive state of other aspects of magnetic recording, however, and Carlson and Carpenter's achievement was largely ignored.
• When the probe and surface are in contact, an AC bias is applied, generating capacitance variations in the sample which can be detected using a GHz resonant capacitance sensor.
• The reduction in distortion and noise provided by AC bias was rediscovered in 1940 by ( 1907 1944 ), while working for at the Reichs-Rundfunk-Gesellschaft ( RRG ).
• Possibly independently of Weber and Braunm黨l, the UK company Boosey & Hawkes produced a steel-wire recorder under government contract during the Second World War that was equipped with AC bias.
• Magnetic media are inherently non-linear, but AC bias was the means whereby the magnetisation of the recording tape was made linearly proportional to the electrical signal which represents the audio component.
• The first rediscovery seems to have been by Dean Wooldrige at Bell Telephone Laboratories, around 1937, but the BTL lawyers found the original patent, and simply kept silent about their rediscovery of AC bias.
• It was introducing an AC signal to the tape, and this was quickly adapted to new models using a high-frequency AC bias that has remained a part of audio tape recording to this day.
• Tape formulation affects the retention of the magnetic signal, especially high frequencies, the frequency linearity of the tape, the S / N ratio, print-through, optimum AC bias level ( which must be set by a technician aligning the machine to match the tape type used, or more crudely set with a switch to approximate the optimum setting . ) Tape formulation varies between different tape types ( ferric oxide [ Fe 2 O 3 ], chromium dioxide [ CrO 2 ], etc . ) and also in the precise composition of a specific brand and batch of tape . ( Studios therefore generally align their machines for one brand and model number of tape and use only that brand and model . ) Backing material type and thickness affect the tensile strength and elasticity of the tape, which affect wow-and-flutter and tape stretch; stretched tape will have a pitch error, possibly fluctuating.