The **DMS-20RM-3-DC2-R-C** is a high-precision, subminiature RMS AC-to-DC digital voltmeter manufactured by Murata Power Solutions. It is designed to measure the True RMS value of complex AC waveforms. --- ### ## Technical Specifications The following table summarizes the core electrical and mechanical characteristics of the module: | Parameter | Specification | | :--- | :--- | | **Display Type** | 3.5 Digit LED, 0.37" (9.4mm) height | | **Display Color** | Red (High intensity) | | **Input Range (AC)** | 0 to 200V RMS | | **Input Frequency** | 47Hz to 1kHz | | **Supply Voltage (DC)** | +7.5 to +28V DC | | **Operating Current** | ~45mA @ 12V | | **Accuracy** | ±0.5% of full scale | | **Package Style** | 12-pin DIP (Epoxy encapsulated) | --- ### ## Core Electronic Components & Architecture The internal circuitry of the DMS-20RM series is highly integrated to maintain its small form factor. Key electronic blocks include: 1. **True RMS-to-DC Converter:** Unlike standard meters that average the signal and multiply by 1.11, this part uses an integrated circuit to calculate the actual heating value of the waveform. This allows it to accurately measure non-sinusoidal waves (Triangular, Square, or Chopped waves). 2. **A/D Converter (Analog-to-Digital):** The module utilizes a precision dual-slope integrating converter to ensure high noise rejection and stability over temperature fluctuations. 3. **Internal Voltage Reference:** A bandgap reference is used to ensure the accuracy of the 200V scale does not drift with changes in the DC supply voltage. 4. **LED Driver Circuitry:** The 3.5-digit display (maximum reading of "199.9") is driven by a multiplexed controller to minimize power consumption and heat generation within the encapsulated package. --- ### ## Pinout Configuration The device is packaged in a 12-pin format. Below are the primary functional pins: * **Pins 1 & 12:** +V Supply and -V Supply (7.5-28V DC input). * **Pins 11 & 10:** AC Input High and AC Input Low (The signal being measured). * **Decimal Point Pins:** Allows manual setting of the decimal point via jumpers/wiring. --- ### ## Key Application Notes * **Isolation:** The DC power supply input is typically isolated from the AC measurement inputs, preventing ground loops. * **Encapsulation:** The "C" suffix denotes a ruggedized, moisture-resistant design suitable for harsh industrial environments. * **Input Impedance:** High input impedance (typically ~1MΩ) ensures that the meter does not load the circuit it is measuring.