Selection Guide

Product Selection Guide

From signal switching to high-voltage disconnects. A comprehensive guide to choosing the right MiRelay technology for your application.

Step 1: Technology

Reed Relay vs. EMR vs. SSR

Why choose a Reed Relay? Understand the fundamental differences.

Feature Reed Relay EMR (Armature) Solid State (SSR)
Switching Speed Fast (0.5 – 1ms) Slow (10 – 20ms) Instant (< 0.1ms)
Contact Resistance Very Low (< 150mΩ) Low (< 100mΩ) High (Voltage Drop)
Isolation Excellent (>10¹² Ω) Good Fair (Leakage Current)
Signal Integrity Excellent (Linear) Good Poor (Distortion)
Life Expectancy High (10⁹ Ops) Medium (10⁶ Ops) Infinite
Verdict: Choose Reed Relays for ATE, Instrumentation, and applications requiring high speed, high isolation, and low signal distortion.
Step 2: Configuration

Understanding Contact Forms

_ / _ 1 Form A (SPST-NO)

Normally Open. The most common type. Contact closes when coil is energized. High isolation.

_ \ _ 1 Form B (SPST-NC)

Normally Closed. Contact opens when coil is energized. Used for fail-safe circuits.

_ / \ _ 1 Form C (SPDT)

Changeover. Switches one common line between a Normally Open and Normally Closed path.

Step 3: Critical Specs

Switching vs. Carry Current

This distinction is the #1 cause of relay selection errors.

Switching Current

The maximum current allowed at the moment the contacts open or close. This is limited by arcing, which damages the contact surface.

  • Dry Reed: Typically 0.5A – 1.0A
  • Mercury Wetted: Typically 2.0A – 5.0A

Carry Current

The maximum current allowed to flow through already closed contacts. This is limited by heating (I²R losses).

  • Dry Reed: Typically 1.0A – 2.5A
  • Mercury Wetted: Typically 5.0A – 10.0A
⚠️ Engineering Rule of Thumb: Never exceed the Power Rating (Watts) even if Voltage and Current are within limits.
Example: A 10W relay switching 200V is limited to 0.05A (P = V * I).
Step 4: Select Series

MiRelay Series Comparison

Series Type Max Voltage Max Carry Key Feature Typical Application
SIP Dry Reed 200V 1.5A Standard Size General ATE, Industrial
MSIP Dry Reed 200V 1.0A Miniature High Density Matrix
HVR Dry Reed 5000V 3.0A High Voltage Cable Testers, Hipot
HGMR Mercury 1000V 2.0A Zero Bounce Precise Instrumentation
HGSR Mercury 2500V 5.0A High Power Pulse Generators
Reference

How to Read Part Numbers

[Series] – [Coil Voltage] – [Contact Form] [Option]
Series
SIP
MSIP
HGMR
Coil
05 = 5V
12 = 12V
24 = 24V
Form
1A = 1 Form A
1C = 1 Form C
2A = 2 Form A
Option
D = Diode
S = Shield
H = High Volt

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