High voltage reed relays show up in test systems, medical diagnostic equipment, and industrial controls, and in all three the relay is usually the least visible part of the signal chain. That is exactly why selection mistakes surface late, during certification or in the field. This guide covers the specifications that actually determine whether a relay will hold up in your circuit.
Dielectric strength comes first
Dielectric strength, or breakdown voltage, is the maximum voltage the relay can withstand without arcing or breakdown. It is the spec to settle before anything else, because it eliminates most of the product list in one pass.
Common ranges in the HVR series:
- 4–6 kV: low-power testing and basic insulation monitoring
- 10–12 kV: the most common choice for general industrial high voltage testing
- 15–20 kV: specialized applications that need extra insulation margin
Choose a breakdown rating at least 20% above your maximum working voltage. Voltage transients and long-term aging both eat into the margin, and the 20% headroom is cheaper than a redesign.
Switching current
Reed relays carry much less current than contactors, and that is fine for their intended jobs. The HVR series covers the usual spread: 0.5 A for signal-level measurement and test, 1 A for general purpose switching, and 2 A where the load demands more. If your design needs more than that, the answer is a DC contactor, not a bigger reed relay.
Package and mounting
- Through-hole: traditional PCB assembly, lowest cost
- Surface mount: high-volume automated assembly
- Modular (HRM series): multi-channel high voltage switching in one block
Creepage and clearance
At high voltage, physical spacing matters as much as the relay’s internal rating. All of our relays are built with proper creepage and clearance distances for their voltage class, but the PCB layout has to cooperate: keep copper spacing generous around the HV pads, or the arc will track across the board instead of staying inside the relay.
Application-to-model reference
| Application | Recommended | Dielectric | Current |
|---|---|---|---|
| BMS insulation testing | HVR-XX10 | 10 kV | 1 A |
| Medical X-ray equipment | HVR-XX15 | 15 kV | 1 A |
| Multi-channel ATE | HRM series | 1–5 kV per channel | 0.5 A |
| Cable insulation testing | HVR-XX20 | 20 kV | 0.5 A |
| Capacitor charging | HVR-XX05 | 5 kV | 2 A |
Mistakes worth avoiding
Underrating the voltage requirement. Always add the safety margin. Arcing at high voltage can destroy the surrounding circuit, not just the relay.
Ignoring contact resistance. High contact resistance means heat and measurement error. Our relays are specified below 50 mΩ.
Forgetting mechanical life. High-cycle applications need a relay rated for the duty. Our reed relays are rated beyond 10⁷ operations.
Skimping on PCB layout. Even a properly rated relay will flash over if the copper spacing around it is too tight. The layout guidelines in the datasheet exist for a reason.
Where to go next
SHR has manufactured high voltage reed relays for over 15 years under IATF 16949 certified quality control, with 100% electrical testing on every unit before shipment and custom designs available for unusual requirements. If you are not sure which model fits, send the requirements to our engineering team and we will recommend one: [email protected].