The **E5C2-R20PD** is a popular analog temperature controller manufactured by Omron. It is known for its simplicity, reliability, and DIN-rail mounting capability. Below is a breakdown of its electronic components, specifications, and operational logic. --- ### 1. Key Technical Specifications The E5C2-R20PD belongs to the E5C2 series. The specific suffixes (R, 20, P, D) indicate its internal hardware configuration. | Feature | Specification | | :--- | :--- | | **Input Type** | Platinum Resistance Thermometer (Pt100) | | **Control Method** | ON/OFF Control (PD control available in some variations) | | **Output Type** | Relay Output (SPDT) | | **Mounting** | 8-pin Round Socket (DIN rail or panel) | | **Supply Voltage** | 100 to 240 VAC (Standard) | | **Contact Rating** | 3A at 250 VAC | --- ### 2. Electronic Component Breakdown The device functions through four main internal stages: #### A. Input Section (Sensor Interface) * **Pt100 Interface:** The "P" in the model name signifies it is designed for **Pt100** RTD sensors. * **Bridge Circuit:** Internally, it uses a Wheatstone bridge or a constant current source to measure the resistance change of the Pt100 sensor as temperature fluctuates. * **Calibration Potentiometer:** Located on the front face, this allows the user to manually set the target temperature (Setpoint). #### B. Control & Comparison Circuit * **Comparator IC:** Unlike modern digital controllers with microprocessors, the E5C2 often uses analog comparators. It compares the voltage from the Setpoint dial against the voltage coming from the Pt100 sensor. * **Hysteresis Logic:** To prevent the relay from "chattering" (rapidly switching on/off) when the temperature is exactly at the setpoint, it includes a small built-in hysteresis (usually 0.5% of the full scale). #### C. Output Section (Power Control) * **Electromechanical Relay:** The "R" in the model indicates a **Relay output**. * **Contacts:** It typically features a Single Pole Double Throw (SPDT) relay. * **LED Indicator:** A front-panel LED lights up (usually red) when the relay is energized (Heating is ON). #### D. Power Supply Section * **Transformer/Switching Supply:** Internal circuitry to step down 110/220VAC to low-voltage DC (5V or 12V) to power the internal comparators and the relay coil. --- ### 3. Pin Configuration (8-Pin Socket) The E5C2-R20PD uses a standard 8-pin circular base. The wiring logic is generally as follows: | Pin Number | Function | | :--- | :--- | | **2 & 7** | Power Supply (AC Input) | | **1, 8, 7** | Output Relay (Common, NO, NC) | | **4, 5, 6** | Pt100 Input (A, B, B' terminals) | --- ### 4. Summary of Model Naming (E5C2-R20PD) * **E5C2:** Series Name (Analog Controller). * **R:** Relay Output. * **20:** Indicates the specific housing/feature set. * **P:** Pt100 Resistance Thermometer input. * **D:** DIN-track mounting / Plug-in type. ---