Here is a detailed list of common analog input devices used with Programmable Logic Controllers (PLCs):
1. **Temperature Sensors:**
- **Thermocouples:** Measure temperature based on the voltage difference between two different metals.
- **Resistance Temperature Detectors (RTDs):** Measure temperature by correlating the resistance of the RTD element with temperature.
- **Thermistors:** Measure temperature based on resistance changes in response to temperature changes.
2. **Pressure Sensors:**
- **Strain Gauge-based Pressure Transducers:** Measure pressure by the deformation of a strain gauge.
- **Piezoelectric Pressure Sensors:** Measure pressure changes using piezoelectric materials.
- **Capacitive Pressure Sensors:** Measure pressure by changes in capacitance caused by pressure-induced displacement.
3. **Flow Sensors:**
- **Differential Pressure Flow Meters:** Measure flow rate by the pressure drop across a restriction.
- **Electromagnetic Flow Meters:** Measure flow based on the voltage generated by a conductive fluid moving through a magnetic field.
- **Ultrasonic Flow Meters:** Measure flow rate using the Doppler effect or transit-time difference of ultrasonic signals.
- **Turbine Flow Meters:** Measure flow rate by the rotational speed of a turbine within the flow.
4. **Level Sensors:**
- **Ultrasonic Level Sensors:** Measure the level of a substance by the time delay of reflected ultrasonic waves.
- **Capacitive Level Sensors:** Measure the level based on changes in capacitance.
- **Radar Level Sensors:** Measure the level using microwave radar pulses.
- **Hydrostatic Pressure Level Sensors:** Measure the level by the pressure exerted by the fluid column.
5. **Displacement Sensors:**
- **Linear Variable Differential Transformers (LVDTs):** Measure linear displacement based on inductive changes.
- **Potentiometers:** Measure displacement through the resistance change of a sliding contact.
- **Magnetic Displacement Sensors:** Measure displacement using magnetic fields.
6. **Humidity Sensors:**
- **Capacitive Humidity Sensors:** Measure humidity based on changes in capacitance due to humidity changes.
- **Resistive Humidity Sensors:** Measure humidity based on changes in resistance.
7. **pH Sensors:**
- **Glass Electrode pH Sensors:** Measure pH based on the potential difference across a glass membrane.
- **ISFET pH Sensors:** Measure pH using ion-sensitive field-effect transistors.
8. **Conductivity Sensors:**
- **Electrodeless Conductivity Sensors:** Measure conductivity without direct electrical contact with the solution.
- **Contacting Conductivity Sensors:** Measure conductivity by direct contact with electrodes.
9. **Light Sensors:**
- **Photodiodes:** Measure light intensity based on the current generated by light exposure.
- **Phototransistors:** Measure light intensity based on the current change in a transistor.
10. **Vibration Sensors:**
- **Piezoelectric Accelerometers:** Measure vibration based on voltage generated by piezoelectric materials.
- **Velocity Sensors:** Measure vibration speed.
11. **Position Sensors:**
- **Encoders:** Measure the position, typically rotary or linear, using optical or magnetic sensing.
- **Hall Effect Sensors:** Measure position or displacement using changes in magnetic fields.
These analog input devices convert various physical phenomena into electrical signals that can be read by the analog input modules of PLCs, enabling precise control and monitoring of industrial processes.