The **FST120** typically refers to a high-performance **Fiber Optic Splice Tray** or a specific series of **Digital Pressure Transmitters/Sensors** (often used in industrial automation). Given the context of "electronic parts," the following breakdown focuses on the **FST120 Pressure Transmitter**, as it contains a complex PCBA (Printed Circuit Board Assembly) and sensor components. --- ## 1. Core Electronic Components of FST120 The FST120 series is an industrial-grade sensor designed to convert physical pressure into an electrical signal (4-20mA or 0-10V). | Component | Function | Material/Type | | :--- | :--- | :--- | | **Sensing Element** | Detects physical pressure changes. | Diffused Silicon or Piezoresistive | | **ASIC Chip** | Signal conditioning and temperature compensation. | High-precision Integrated Circuit | | **Amplifier Circuit** | Converts the weak millivolt signal to standard output. | Operational Amplifiers (Op-Amps) | | **Protection Diode** | Prevents damage from reverse polarity. | Schottky or Zener Diodes | | **EMC Filter** | Reduces electromagnetic interference (EMI). | Capacitors and Inductors | --- ## 2. Technical Architecture The device is structured into three main electronic layers: ### A. The Sensor Head This is the "front end" of the electronics. It contains a diaphragm and a Wheatstone bridge circuit. When pressure is applied, the resistance of the bridge changes, creating a small voltage differential. ### B. Signal Conditioning Unit * **A/D Converter:** Converts the analog voltage from the sensor into a digital value. * **Microcontroller (MCU):** Applies calibration coefficients to ensure accuracy across different temperatures. * **D/A Converter:** Converts the processed digital data back into an analog current loop (usually **4-20mA**). ### C. Connection & Interface * **Hirschmann Connector / M12 Plug:** The physical electronic interface for power input and signal output. * **Potentiometers:** (In older or adjustable models) Used for Zero and Span manual calibration. --- ## 3. Electrical Specifications | Parameter | Typical Value | | :--- | :--- | | **Input Voltage** | 12-36V DC | | **Output Signal** | 4-20mA (2-wire) / 0-5V / 0-10V | | **Load Resistance** | $(U - 12V) / 0.02A$ | | **Insulation Resistance** | $> 100M\Omega$ @ 50V | --- ## 4. Key Features of the Electronics * **Temperature Compensation:** Built-in thermistors or internal MCU logic adjust the output to prevent "drift" when the environment gets hot or cold. * **Reverse Polarity Protection:** The internal circuitry is designed so that if the $(+)$ and $(-)$ wires are swapped, the electronics will not burn out. * **Short Circuit Protection:** Limits current flow to prevent damage during a fault.