Regardless of the ADC board type, you mustįor it by specifying its name on the ADC line of theĪSCII stands for American Standard Code for Information System motherboard, so they don't need a separate board. Machines come with sound card functionality built into the Plug into a printer port to provide ADC functions. In this, as well as PCMCIA cards and special modules that can SoundĬards and laboratory data acquisition cards are thus included
Must install into your computer to provide the ADC. Since PC-type computers don't usually haveīuilt-in ADC facilities, this just refers to a board that you Throughout this Daqarta Help text, you will see references to Next command to begin another conversion. "latched" on the ADC output lines, and the ADC waits for the When all are done, the final digital value is Thus requires 8 separate set-and-test operations, each givingĪ successively better approximation to the true analog input In like manner, each successive bit is tested. Now have a "two bit" approximation to the input. New bit is left set or cleared depending on the outcome. The DAC will now be at 3/4 if the first bit Then the next bit is set, adding a quarter-scale voltage to either it is or is not as big as half-scale. We have thus "approximated" the input voltage by a single bit Part of the final output, otherwise it is cleared to zero. If the input voltage isĪt least half of full-scale, then that bit will remain set as This corresponds to setting the most significant bit
(and hence a DAC output voltage) that is half of the full The successive approximation scheme begins with a trial number Trial number is increased or decreased as needed and the final To Analog Converter ( DAC) and compared to the held input. Number is converted back to an analog voltage with a Digital Method is called "successive approximation", wherein a trial Source, the ADC will "sample" the input voltage very brieflyĪnd hold that value as a charge on a capacitor, using aĬircuit called a "Sample and Hold" (S/H) or "Track and Hold"ĭuring the "hold" time, the held analog voltage is converted to aĭigital number by any of several means. On a command from the computer, a timer, or an external Most modern ADC boards have 12 or 16 bits. "quantization error", and can be reduced by using an ADC with Resolution will be 20 / 256 or 0.078125 Volts at best. Must handle the entire +/-10 Volt range (20 Volts), then It can only encode 256 possible values (2^8 = 256). The analog input can thus have "infinite" resolution, but theĪDC output will be limited according to the number of bits it can use ForĮxample, if the ADC is specified to handle +/-10 Volts, anĪnalog input of +1.234567 Volts is perfectly valid.
May take any value within the ADC's specified range. ADC inputsĪre almost always voltages (as opposed to currents), and This device (also abbreviated A/D) converts real-world analogĭata into the digital form needed by the computer. Daqarta for DOS Data AcQuisition And Real-Time Analysis Shareware for Legacy Systems