Remote Sensors and Power Supply
Remote sensors are increasingly being powered by digital and integrated analog power supplies. Decentralized and compact electronic circuits in industrial applications like encoders, controls, laser modules or light barriers are primarily powered through 24V long lines.
It is not unusual to find this fluctuating between +/- 50%. Low frequency noise and glitches are other problems. That is why embedded engineers are increasingly recommending custom power supplies to power remote sensors.
In sensor technology, the analog circuits are high precision which means the voltage that you supply to the circuit must be as glitch-free and precise as possible. Supply voltage tolerance in digital circuit microcontrollers and other parts should be within a range of plus or minus 5%. The ripple must be less than 50mV.
On the other hand, if the sensor has both digital and analog circuit components, you are going to need two supply voltages. For instance, in the sensors we use today, microcontrollers and drivers with switching capability of many 100 mA (like RS422 line drivers and IO link interface drivers) work in combination with analog circuits (high precision).
This combination is not without its problems. It can result in cross talk, ground displacements and supply voltage glitches. Embedded engineers must pay attention to all these issues when designing custom power supplies for remote sensors.
