Discussion
An ADC used in \(3\frac{1}{2}\) (Three and half) digital multimeter is generally :
Answer: A
A 3½ digit multimeter generally uses a 12 bit dual slope ADC.
A 3½ digit display reads up to ±1999, about 2000 counts, which needs a resolution of at least 11 bits (\(2^{11} = 2048\)); a 12-bit-class converter covers it. Digital multimeters use the dual slope (integrating) method because it is accurate, cheap and rejects mains-frequency noise by integrating over a whole number of cycles; speed does not matter for a meter that updates a few times a second. Single-chip converters such as the ICL7106 are built for exactly this.
An 8-bit converter gives only 256 levels, far too few for 2000 counts, whatever its type, so all three 8-bit options are wrong.
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