Sensor Types Recap
| Sensor Type | Signal Type | Power Supply | Examples | Notes |
| Analog | Continuous (4-20 mA, 0-10 V, ±10 V, ±5 V) | Loop-powered or external | RTDs, Thermocouples, Pressure sensors | Provide continuous measurement |
| Digital | Discrete ON/OFF (24 V DC) | External (usually 24 V) | Proximity sensors, Limit switches, Push buttons | Provide binary signals |
How Sensors Work
- Analog sensors: Measure physical parameters and convert them into continuous electrical signals proportional to the measured variable. Passive sensors need excitation; active sensors generate their own signal
- Digital sensors: Detect state changes or presence/absence of a condition and output discrete signals.
Testing and Troubleshooting Methods
| Sensor Type | Testing Tools | Key Checks | Comments |
| Analog (4-20mA) | Loop calibrator, multimeter | Current measurement, simulation, loop powering | Check for correct current range and faults |
| Analog (Voltage) | Multimeter, oscilloscope | Voltage levels, wiring integrity | Check for voltage drops and noise |
| Digital | Multimeter, test lamp | Voltage presence, ON/OFF response | Check wiring, input recognition by PLC |
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