The HM05-1A69-150 is a high-voltage reed relay from Standex Electronics, sold under the MEDER electronic brand. It is built for applications that need serious high-voltage isolation in a PCB-mount package: high-voltage test sets, cable testers, and medical equipment such as RF surgery systems. The numbers that define it: a 5 VDC coil, one Form A (SPST-NO) contact, switching up to 10 kVAC/10 kVDC and 3 A, 50 W maximum switched power, and a 15 kVDC breakdown voltage.
Technical specifications
| Characteristic | Value |
|---|---|
| Coil voltage | 5 VDC |
| Coil resistance | 30 Ω |
| Coil current (max DC) | 0.167 A |
| Coil power | 833 mW |
| Contact form | 1 Form A (SPST-NO) |
| Max switched current | 3.0 A (DC or peak AC) |
| Switching voltage | 10 kVAC, 10 kVDC |
| Max switched power | 50 W |
| Static contact resistance (max) | 150 mΩ |
| Insulation resistance (typ.) | 10¹³ Ω (contacts, and contact to coil) |
| Breakdown voltage | 15 kVDC |
| Dielectric strength coil/contact | 15 kVDC (per EN 60255-5) |
| Coil suppression diode | None; external suppression required |
| Operate time incl. bounce | 3.0 ms |
| Release time | 1.5 ms (without suppression) |
| Capacitance across open switch | 0.8 pF typ. |
| Capacitance contact to coil | 5.0 pF typ. |
| Operating temperature | −20 °C to +70 °C |
| Storage temperature | −35 °C to +105 °C |
| Soldering temperature | 260 °C for 5 s |
| Shock resistance | 50 g (11 ms, ½ sine) |
| Vibration resistance | 20 g (10–2000 Hz) |
| Life expectancy | 50 × 10⁶ cycles at 5 V / 10 mA DC |
| Body dimensions | 68 × 19 × 19.8 mm |
| Termination | Axial cables, AWG20 silicone HV wire (UL 3239), tinned ends |
| Construction | Sealed, epoxy encapsulated, magnetic shield; polycarbonate housing, polyurethane sealing compound |
A few of these numbers deserve comment. The insulation resistance of 10¹³ Ω is what keeps leakage currents negligible in test sets and patient-connected medical circuits, and the 15 kVDC breakdown voltage leaves real margin over the 10 kV switching rating. The 0.8 pF open-contact capacitance is low enough that the relay does not meaningfully load or distort high-frequency signals in ATE service.
The axial cable termination is the point
The “150” suffix in the part number is the axial cable option: pre-attached AWG20 silicone high-voltage wire for direct wiring, sometimes called sky wiring. This is the design answer to a real problem: at 10 kV, maintaining adequate creepage and clearance on a PCB is hard, and the cable termination moves the high-voltage routing off the board entirely. It reduces layout risk on cable testers and medical equipment where the high-voltage connection integrity is the whole game. The HM series also serves as a modern mercury-wetted relay replacement, matching the low contact resistance and long life without mercury in the bill of materials.
Availability and pricing
This is a niche part, not a commodity, and the sourcing picture reflects that. Major authorized distributors frequently show zero stock; Mouser lists it as non-stocked with a 10-week factory lead time and a 20-unit minimum order, with tiered pricing at $44.19 per unit at 20 pieces and $36.39 at 200. Okmarts claims stock with 1–5 day shipping but at $165.38 per unit, a price that suggests independent or grey-market inventory rather than authorized distribution. Treat any “in stock” claim at a large price premium with appropriate caution.
| Distributor | Stock Status | Lead Time | MOQ | Unit Price (USD) |
|---|---|---|---|---|
| Mouser Electronics | Non-stocked | 10 weeks | 20 (multiples of 20) | $44.19 @ 20, $36.39 @ 200 |
| TTI Asia | 0 in stock / not online | Contact sales | — | — |
| Okmarts | In stock | 1–5 days | — | $165.38 |
| Mobicon-Remote, Jotrin | Quote on request | Quote | Quote | Quote |
Authorized Standex/MEDER distribution also runs through DigiKey, TTI, Heilind, Master Electronics, TME, and others in most regions. The practical takeaway for project planning: this part moves in small batches and build-to-order quantities, so engage distributors early and treat the 10-week lead time as the planning baseline, not the exception.
How these relays fail
Current inrush is the main killer. The relay’s power rating assumes the product of the voltage across the open contacts just before closure and the current at the moment they make. Discharging a capacitive load is worse than charging one, because the current is limited only by the reed switch and trace resistance; even a modest capacitor can deliver tens of amps for microseconds, and stored energy scales with ½ CV². A severe inrush welds the contacts shut on closure; a milder one transfers material over time, building a pip on one contact and a crater on the other until they interlock mechanically.
Reactive loads need respect. Purely resistive loads are where reed relays are happiest. Inductive loads arc on opening; limit the back EMF with a diode for DC or a snubber or varistor network for AC.
Magnetic interaction. Relay coils are electromagnets, and a neighboring relay’s field opposes the one beside it. Pack small relays closely and the required operate voltage can rise by as much as 40%. Form B and latching types, with their permanent magnets, are the worst neighbors.
Temperature. Coil resistance rises 0.39% per °C. A 30 °C rise means roughly 12% more resistance and 14% less coil power, which erodes the overdrive and with it the life expectancy. Internal temperature includes self-heating from carry current (I²R), not just ambient.
End-state failures come in three modes: sticking (fails to open), missing (fails to close), and contact resistance drift. Manufacturers distinguish soft failures, where the relay recovers within about half a second, from hard failures where it does not. ATE-grade life estimates count the first soft failure as end of life, which tells you how the tolerance for glitches is set in this industry.
Getting the full life out of it
- Cold switch wherever possible. Apply the stimulus after the contacts have settled and remove it before opening; this alone can extend life dramatically in test systems.
- Keep the overdrive up. The 5 V part has a “must operate by” voltage around 3.8 V; hold the coil at least 25% above that. Avoid driver ICs that drop the coil voltage after closure to save power, because most reed relays do not have enough pull-in to drop-out margin to tolerate it.
- Protect the coil circuit. The standard part has no internal suppression diode, so add the external diode; keep relay coils on a supply separate from sensitive analog rails.
- Watch the thermals. Keep ambient down, and where carry current is high, allow for I²R self-heating before judging the coil drive margin.
- Space and shield. Allow at least 5 mm between adjacent relays, alternate the orientation of magnet-equipped types end-to-end, and prefer ferrous shells or internal magnetic shielding in dense layouts.
Where the part is used
The three core applications: high-voltage test sets for insulation and breakdown testing, cable testers (including the capacitive discharge management that follows proof testing), and medical equipment such as RF surgery systems, where the isolation and energy control requirements are strict. The wider HM series from Standex/MEDER also serves industrial, automotive, appliance, alternative energy, HVAC, consumer, and military/aerospace designs, but the 1A69-150’s axial cable termination and 10 kV rating point it squarely at the most demanding high-voltage corner of that range.
In short: a specialized, high-isolation reed relay with genuine 10 kV switching and 15 kV breakdown capability, an axial cable termination that takes high-voltage routing off the PCB, and a supply chain that rewards early planning. Design it in with attention to inrush, coil overdrive, thermals, and layout, and it will deliver the reliability the specification promises.
For selection guidance on high voltage reed relays more broadly, see how to choose the right high voltage reed relay and our high voltage reed relay product range, or use the product finder to match a specification.