What we like to do, is provide actual measured data that tells you the resolution of a device including typical inherent noise. It is hard to simply state "the resolution" of a given device. The simple fact that a converter returns 16-bits says little about the quality of those bits.
When an ADC chip returns 16 bits, it is probably better than a 12-bit converter, but not always. When you see analog input DAQ devices from various manufacturers called 12-bit, 16-bit, or 24-bit, it generally just means they have an ADC (analog to digital converter) that returns that many bits. What does it mean to say a device is 12-bit, 16-bit, or 24-bit? This gives a voltage resolution of 20/4096 or 0.00488 volts per bit (4.88 mV/bit). In the case of the LabJack U12, a single-ended analog input has a voltage range of -10 volts to +10 volts (20 volt total span) and returns a 12-bit value. Low voltages give a 0 and high voltages give a 1. It might occur to you at this point that a digital input could be thought of as a 1-bit analog to digital converter. A 16-bit digital value can represent 65536 (2 16) different numbers. A 12-bit digital value can represent 4096 (2 12) different numbers. A 3-bit digital value can represent 8 (2 3) different numbers.
So in this example, the 2-bit digital value can represent 4 different numbers, and the voltage input range of 0 to 10 volts is divided into 4 pieces giving a voltage resolution of 2.5 volts per bit. This device will give digital values as follows:
Now, say you have a device which converts an analog voltage between 0 and 10 volts into a 2-bit digital value for storage in a computer. If you are storing a digital 2-bit number you can store 4 different values: 00, 01, 10, or 11.
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A computer is a digital machine and thus stores a number as a series of ones and zeroes. Resolution in this context refers to the conversion of an analog voltage to a digital value in a computer (and vice versa).
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