### Overview of E5C4-R20P The **E5C4-R20P** is a compact, analog-setting temperature controller commonly used in industrial heating systems. It belongs to the Omron E5C4 series, designed for DIN rail mounting and ease of operation. --- ### Key Technical Specifications The "R20P" suffix indicates specific electronic and output characteristics. | Feature | Specification | | :--- | :--- | | **Input Type** | Platinum Resistance Thermometer (Pt100) | | **Output Type** | Relay Output (SPDT) | | **Control Method** | ON/OFF or proportional (P) control | | **Power Supply** | 100 to 240 VAC (50/60 Hz) | | **Mounting** | 8-pin socket (DIN track or panel mount) | | **Setting Method** | Analog dial (Potentiometer) | --- ### Electronic Components & Functions #### 1. Input Section (Pt100 Sensor) The "P" in the model name signifies that it is designed for **Pt100 RTD** (Resistance Temperature Detector) sensors. - **Bridge Circuit:** Internally, the device uses a Wheatstone bridge or similar precision circuit to measure the resistance changes of the Pt100 sensor. - **Cold Junction:** Unlike thermocouples, this unit measures resistance, so it requires high-precision internal resistors to maintain accuracy. #### 2. Control Output (Relay) The "R" in the model name stands for **Relay**. - **Internal Relay:** It contains a physical electromagnetic relay. - **Rating:** Typically rated at **250 VAC, 3A** (resistive load). - **Function:** When the measured temperature is lower than the set point (in heating mode), the internal coil energizes, closing the contact to power the heater. #### 3. Power Supply & Isolation - **Transformer/Switching Circuit:** Converts the 100-240 VAC mains voltage to low-voltage DC (typically 12V or 24V) to power the internal logic. - **Galvanic Isolation:** The input (sensor) and output (relay) sections are electronically isolated to prevent high-voltage surges from damaging the sensor or the user interface. #### 4. Setting & Logic - **Analog Potentiometer:** Instead of a digital screen, it uses a high-precision potentiometer linked to the front dial. This provides a reference voltage to a comparator circuit. - **Comparator/Op-Amp:** The controller compares the voltage from the Pt100 input against the reference voltage from the dial. - **Hysteresis Circuit:** Includes a small temperature gap (usually 2°C) to prevent the relay from "chattering" (rapidly switching on and off) when the temperature is exactly at the set point. --- ### Pin Configuration (8-Pin Socket) To integrate the E5C4-R20P, the following electronic connections are standard: | Pin Number | Function | | :--- | :--- | | **2 & 7** | Power Supply (100-240 VAC) | | **1, 8, 7** | Relay Contacts (COM, NO, NC) | | **3, 4, 5** | Pt100 Input (3-wire compensation) |