Analog versus Digital Sensors

A number of sensors produce analog output signals rather than digital signals. This means an A/D converter  is required to connect such a sensor to a microcontroller. Typical examples of such sensors are:
• Microphone
• Analog infrared distance sensor
• Analog compass
• Barometer sensor
Digital sensors on the other hand are usually more complex than analog sensors and often also more accurate. In some cases the same sensor is available in either analog or digital form, where the latter one is the identical analog sensor packaged with an A/D converter.

The output signal of digital sensors can have different forms. It can be a parallel interface (for example 8 or 16 digital output lines), a serial interface (for example following the RS232 standard) or a “synchronous serial” interface.

The expression “synchronous serial” means that the converted data value is read bit by bit from the sensor. After setting the chip-enable line for the sensor,the CPU sends pulses via the serial clock line and at the same time reads 1 bit of information from the sensor’s single bit output line for every pulse (for example on each rising edge). See photo below for an example of a sensor with a 6bit wide output word.