Analog-Digital Converters, or ADCs, are devices which measure an analog voltage signal as a digital number. These devices are commonly used to allow embedded computing systems to interpret analog sensors.
ADCs generally come in a small chip package, and must be soldered onto a PCB board before they can be used. To collect data from these devices, or to configure them, a SPI, I2C, or CAN interface is typically implemented. Some of the prongs on the chip package will serve as the input prongs.
There are many specifications which define an ADC. Choosing an ADC with the right set of specifications is important to achieving proper system functionality. The information on any particular ADC's specs are usually found in its data sheet. Here are several of the most important specs for an ADC:
The sampling rate is the rate at which voltage samples can be measured, and is typically measured in Samples per Second (SPS). ADCs can have sampling rates of only a few dozen SPS up to several millions of SPS. Obtaining ADCs which measure several tens of thousands of samples per second (kSPS) is relatively easy.
The precision is the number of bits of data per sample that can be taken. A higher precision generally means more precise voltage measurements. For example. a 12-bit ADC can sample with 4 times the precision as an equivalent 10-bit ADC, since it has two extra bits of data.
All ADCs have a predefined voltage range over which they can measure. The ADC could potentially be damaged if the voltage difference exceeds the range.
The Minimum Voltage Increment is the smallest voltage increment which can be measured by the ADC. This depends on both the voltage range and the precision of the ADC.
This simple formula can be used to calculate the voltage resolution:
For example, if an ADC has a resolution of 18 bits, and the voltage ranges from -2.048V to 2.048V, then the min voltage increment is:
Increasing the voltage range will also increase the minimum voltage increment. Increasing the precision increases the minimum voltage increment. It is important to ensure that the minimum voltage increment in your application is small enough to offer precise measurements.