PH4705 & ET4305: Digital Sensors. Simple switches to data words Switch: micro-switch, reed relay, Hall sensor, optical switch….. Threshold or Set point detector Counting, timing, finding the frequency Sensors that generate data words directly
Simple switches to data words
Input ON/OFF information
reed relay operated by a magnet
Hall effect sensor
LDR-light dependant resistor
Slotted and reflective sensors
Logic Signal input
Compatible logic signal (voltage levels, available current)?
Interference and noise?
Threshold or Set Point Detection
Analogue input signal, detect when its value passes through a set point or threshold (in either direction)
Zero crossing detector
Threshold or Set Point detector
Threshold detector with hysteresis
Counting, timing, finding frequency
The required data derived from switch sensors may be:
number of pulses
time between pulses
width of pulse
frequency of pulses ………..
Typical example is this optical coded disc used to detect angular position. Looking along a radius gives an 8-bit word or a resolution of 1/256.
(Looking at the pulse rate of, say, the outside markings will also yield speed.)
Complex IC digital sensor
Sensors system ICs that have signal processing and generate digital data as a serial data streams or connect directly to a microprocessor system data bus.
Examples: CCD digital camera sensor,
SHT75 temperature/humidity module