The **M2AC-AC2-R/CE** is a high-performance **M-System (M-UNIT) Plug-in Signal Conditioner**. Specifically, it is an **AC Current Transmitter** designed to convert an alternating current (AC) input into a standard DC output signal. Below is a detailed breakdown of its electronic components, specifications, and architecture. --- ## 1. Core Technical Specifications The model code breaks down into specific electronic characteristics: | Feature | Specification | | :--- | :--- | | **Model Series** | M2AC (Plug-in AC Current Transmitter) | | **Input Signal** | AC Current (e.g., 0–1A or 0–5A AC) | | **Output (AC2)** | 4 – 20 mA DC (Load resistance max. 750 $\Omega$) | | **Power Input (R)** | 24V DC | | **Standards (CE)** | CE Marking compliant (EMC Directive) | | **Accuracy** | ±0.3% of span | | **Response Time** | $\leq$ 0.5 seconds (0 – 90%) | --- ## 2. Internal Electronic Architecture The device functions through four primary electronic stages: ### A. Input Stage (Transducer) * **CT (Current Transformer):** The device contains an internal step-down transformer that safely isolates the high-amperage AC input from the internal processing circuitry. * **Shunt Resistor:** Converts the scaled AC current into a proportional AC voltage for processing. ### B. Signal Processing (Rectification & Smoothing) * **Precision Rectifier:** Converts the AC voltage waveform into a pulsating DC signal. * **Filtering Circuit:** Uses capacitors and operational amplifiers (Op-Amps) to smooth the ripple, resulting in a stable DC level representing the **Average Value** (calibrated to the RMS of a sine wave). ### C. Isolation Barrier * **Three-Way Isolation:** The electronic design ensures that the **Input**, **Output**, and **Power Supply** are galvanically isolated from one another. This prevents ground loops and protects sensitive PLC/DCS inputs from high-voltage surges on the AC line. ### D. Output Stage * **Current Driver:** A feedback-controlled transistor circuit that ensures the 4–20mA output remains precise regardless of the load resistance (up to 750 $\Omega$). --- ## 3. Terminal Connection Map The M2AC series typically uses an 8-pin or 11-pin base. The "R" variant (24V DC power) follows this general layout: | Terminal No. | Function | Description | | :--- | :--- | :--- | | **1 & 5** | Input | AC Current source (L1 / L2) | | **7 (+)** | Output | 4 – 20 mA DC Positive | | **8 (-)** | Output | 4 – 20 mA DC Negative | | **9 (+)** | Power | 24V DC Positive | | **10 (-)** | Power | 24V DC Negative | --- ## 4. Key Performance Features * **Zero/Span Adjustment:** Accessible via the front panel, allowing for fine-tuning of the electronic calibration without removing the unit. * **High Dielectric Strength:** Usually rated for 2000V AC @ 1 minute, ensuring robust protection against electrical breakdown. * **DIN Rail Mounting:** The electronic housing is designed for standard M-System plug-in bases, allowing for "hot-swapping" without disconnecting field wiring. ---