The **PMS-2-R/Q** is a high-performance, differential pressure monitoring switch, commonly used in industrial HVAC systems, cleanrooms, and filter monitoring applications. This device converts mechanical pressure changes into a discrete electrical signal to trigger alarms or control systems. ### 1. Technical Specifications The core electronic and mechanical parameters are summarized in the table below: | Feature | Specification | | :--- | :--- | | **Switch Type** | Changeover switch (SPDT) | | **Contact Load** | Max. 5 A / 250 V AC (Resistive) | | **Pressure Range** | Typically 20 - 300 Pa or 50 - 500 Pa (Variant dependent) | | **Connection Type** | Screw terminals (usually 3-pole) | | **Cable Entry** | M16 or M20 gland | | **Protection Class** | IP54 (NEMA 3 equivalent) | --- ### 2. Internal Electronic Components The device operates on a mechanical-to-electrical interface. Here is a breakdown of the internal parts: #### A. The Microswitch (The Core) The primary electronic component is a **Snap-action Microswitch**. * **Function:** When the pressure on the internal diaphragm reaches the setpoint, it triggers a mechanical lever that flips the microswitch. * **Contacts:** It features **Silver (Ag) or Gold-plated** contacts to ensure low resistance and prevent oxidation over long periods of inactivity. #### B. Terminal Block The wiring is handled via a three-point terminal block labeled: 1. **COM (Common):** The input line. 2. **NC (Normally Closed):** Connected to COM when pressure is below the threshold. 3. **NO (Normally Open):** Connects to COM when pressure exceeds the threshold (Tripped state). #### C. Adjustment Potentiometer/Dial While the mechanism is mechanical (spring-loaded), the "logic" is set via a calibrated adjustment knob. This determines the compression force required to close the electrical circuit. --- ### 3. Wiring Logic The following code snippet represents the logic used if this switch were integrated into a PLC (Programmable Logic Controller) system to monitor a filter: ```python # Pseudo-code for Pressure Switch Integration def monitor_filter_status(switch_input): if switch_input == "CLOSED": return "ALARM: Filter Clogged / Pressure High" else: return "STATUS: Normal Operation" # Logic for a SPDT Switch # NO (Normally Open) -> Alarms/High Pressure # NC (Normally Closed) -> System Run/Healthy ``` --- ### 4. Application Context * **Filter Monitoring:** Detects the pressure drop across a filter. When the filter is dirty, pressure increases, the diaphragm moves, and the electronic switch triggers a "Change Filter" light. * **Fan Supervision:** Ensures that a fan is actually spinning by detecting the differential air pressure it creates.