H E3600 Min ia tu re S .I.L . R e lay F e a tu re s a n d Be n e fits # Technical Documentation: HE3621A0500 Reed Relay
Manufacturer: HAMLIN
Component Type: Monostable, Form A (SPST-NO) Reed Relay
Primary Function: Low-power signal switching and isolation in precision electronic circuits.
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## 1. Application Scenarios
### Typical Use Cases
The HE3621A0500 is a monostable, single-pole single-throw normally open (SPST-NO) reed relay designed for low-power switching applications. Its hermetically sealed reed switch contacts are encapsulated in a compact, magnetically shielded package, making it suitable for environments where reliability and signal integrity are paramount.
* Low-Level Signal Switching: The primary use case is switching analog signals, low-voltage DC, or low-current AC signals where contact resistance and thermal EMF must be minimized. This includes routing audio signals, sensor outputs (e.g., thermocouples, strain gauges), and precision voltage references in test and measurement equipment.
* High-Impedance Circuit Isolation: Used to connect or disconnect high-impedance nodes in circuits, such as the input stages of operational amplifiers or sample-and-hold circuits, where leakage current from semiconductor switches would introduce error.
* Automatic Test Equipment (ATE): Frequently employed in ATE systems for multiplexing signals from multiple devices under test (DUTs) to a single measurement instrument, benefiting from the relay's excellent isolation and low offset characteristics.
* Safety and Interlock Circuits: Serves as a reliable, fail-safe (normally open) component in safety-critical circuits where a physical break in the signal path is required when de-energized.
### Industry Applications
* Medical Electronics: Patient monitoring equipment, diagnostic devices (e.g., ECG, EEG), and laboratory analyzers where signal fidelity and patient safety isolation are critical.
* Telecommunications: Legacy and specialized communication equipment for channel switching and cross-connect applications, leveraging its high off-state isolation.
* Industrial Control & Instrumentation: Process control systems, data acquisition (DAQ) systems, and programmable logic controller (PLC) I/O modules for switching sensor and control signals in noisy environments.
* Test & Measurement: Precision multimeters, oscilloscopes, source-measure units (SMUs), and scanner cards where accuracy and low thermal drift are essential.
* Aerospace & Defense: Avionics systems and military communications gear that require components with proven reliability and performance under varying environmental conditions.
### Practical Advantages and Limitations
Advantages:
* Excellent Isolation: The hermetically sealed glass envelope provides very high resistance (>10¹⁰ Ω) and high breakdown voltage (>500V) between open contacts and from coil to contacts, minimizing leakage and crosstalk.
* Low and Stable Contact Resistance: Typically <100mΩ, which remains stable over the life of the relay, ensuring minimal voltage drop and signal attenuation.
* Fast Switching Speed: Operate and release times are on the order of milliseconds, suitable for many multiplexing and scanning applications.
* No Semiconductor Junction Effects: Unlike solid-state relays (SSRs), reed relays do not introduce offset voltage, leakage current, or capacitance variation with signal level, making them ideal for precision DC and low-frequency analog signals.
* Long Operational Life: When switched within its rated specifications, it can achieve 10⁸ to 10⁹ operations.
Limitations:
* Limited Current/Voltage Rating: The HE3621A0500 is rated for low-level switching (e.g., 0.5A, 100V). It is not suitable for switching mains power, inductive loads (like motors or solenoids), or high inrush currents without external protection.
* Contact Wear: Mechanical wear occurs with each operation. Switching inductive or capacitive
