Reed Relay life is governed by many factors. The design engineer cannot just look at a series of reed relays and expect that since the specifications look essentially the same that all sizes of reed relays from DIP to POTTED to SIP perform the same. This is a wrong and dangerous assumption.

The standard reed relay utilizes a 10 watt switch that when used in many instances performs very well. Standard switching voltages of about 100 VDC @100 ma. are about the limit for this 10 watt device though. Depending upon.whose switch specifications one reads, the result is an approximate operational life of about 10 million closures and openings at the above load. Contact resistance of the relay usually varies from about 100 milliohms initially to close to a half an ohm at end life. Reed relay life is much longer at reduced power loading. End life is totally unpredictable if one considers that reed relay manufacturers approve many reed switches from many sources for use in standard products, that while meeting physical requirements for relay manufacturing may not all perform the same.

Sometimes design engineers make the mistake of assuming that a relay already approved for use can be used in an entirely new application. Many times this approach works well. The trouble with this approach is that the manufacturer of the relay usually is not contacted about the new requirement until something stops working. A lot of hand wringing and head scratching then takes place and can result in a new reed relay being designed to replace the problem relay, or perhaps results in the problem reed relay being designed out. All these difficulties are averted upon contacting the relay manufacturer prior to using the relay in a new application.

To solve the problem of performance over life, EAC prefers to design the relay using the best of about 150 reed switches available from any number of manufacturers to meet the customer's design criteria. Relays designed in this manner easily meet the customer's requirements while retaining the price structure of the standard relay. Reed relay design is then frozen so that only the approved switch is used in the end product. Switch substitution is not allowed.

Relays so designed can easily meet a 50 watt performance for a million operations if required. The same is true when switching TTL loads for over 500 million operations without measurable sticking. The trick here is to know the customers requirements and to utilize the proper switch and freeze the design.

Working with inductive or capacitive loads requires some protection of the switching contacts. Stray capacitance protection, specifically high common mode voltage is discussed in EAC Engineering Bulletin #6O-01. Refer to this bulletin for a full discourse on the subject. The Nomograph on this bulletin shows how to protect the relay contacts in other instances not covered by Bulletin #60-01, or when using other than pure resistive power loads.

EAC's reed relays are designed to take into consideration all of the known operational parameters. EAC then freezes the design of the relay so that the relays one purchases a few years from now are constructed the same and tested the same as the approved engineering samples.