MIL-PRF-28776 Relays, Hybrid, Established Reliability, General Specification ForThis specification establishes the general requirements for relays that use a combination of solid state circuit input elements functioning with an electro-mechanical relay that performs the switching functions associated with control system applications \(see 6.1\). These relays are designed to operate in low and medium power switching circuits with contact ratings up to 1 ampere alternating current \(ac\) or direct current \(dc\). The failure rate level is established at a confidence level of 90 percent for qualification and 60 percent for maintenance of qualification based on 100,000 cycles at +125┬░C under rated load conditions specified herein. Excludes time delay relays. CAUTION: The use of any coil voltage less than the rated coil voltage will compromise the operation of the relay. CAUTION: Pick-up, hold, and dropout voltages are for test purposes only and are not to be used as design criteria. For additional application and caution information, see 6.1.

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MIL-PRF-28776F

4.8.7.3.2 Coil resistance (see 3.12.3.2). Coil resistance is approximately calculated as follows: The rated voltage

of the coil shall be divided by the coil current.

4.8.7.4 Turn-on voltage (coil supply voltage on) (see 3.12.4). Apply rated coil supply voltage (see 3.1). The turn-

on voltage shall then be applied. Verify that the relay has turned on. Unless otherwise specified (see 3.1), for

qualification inspection, the relay shall be mounted in each of three mutually perpendicular planes. For conformance

inspection, the relay mounting position is optional. A suitable indicating device shall be used to monitor contact

operation.

4.8.7.5 Turn-off voltage (coil supply voltage on) (see 3.12.5). Rated coil supply voltage and control signal voltage

shall be applied to the relay (see 3.1). The control signal shall be reduced to maximum turn-off voltage. Verify that

the relay has turned off (see 3.1). Unless otherwise specified (see 3.1), for qualification inspection, the relay shall be

mounted in each of three mutually perpendicular planes. For conformance inspection, the relay mounting position is

optional. A suitable indicating device shall be used to monitor contact operation.

4.8.7.6 Turn-on time and turn-off time (see 3.12.6). The turn-on time and the turn-off time shall be measured using

an oscilloscope or other acceptable means approved by the qualifying activity. Rated coil supply voltage shall be

applied to the relay during toggling of the control signal. The circuit shown on figure 4, or equivalent, shall be used.

The turn-on time and the turn-off time shall be exclusive of contact bounce. Timing measurements shall be made on

all contact sets.

4.8.7.6.1 Break before make (see 3.12.6.1). The circuit shown on figure 5 or an equivalent circuit approved by the

qualifying activity shall be used to monitor contact position.

4.8.7.7 Contact dynamic characteristics (see 3.12.7).

4.8.7.7.1 Contact bounce (applicable to failure level rate "L") (see 3.12.7.1). Contact bounce shall be measured

on each contact set using an oscilloscope or other acceptable means approved by the qualifying activity. The trace

shall show contact switching at turn-on and turn-off and appropriate timing markers when using an oscilloscope.

Rated voltage shall be applied to the coil. Contacts shall be loaded with 6 V dc maximum or peak ac at 10 mA

maximum. After high level rated load life and intermediate current tests, contact bounce shall be measured at 100

mA maximum at 28 V dc maximum. A contact bounce shall be considered any occurrence equal to or greater than

90 percent of the open circuit voltage with a pulse width of 10 �s or greater. The circuit shown on figure 4, or

equivalent, shall be used.

4.8.7.7.2 Contact stabilization time (applicable to failure rate levels "M", "P", and "R") (see 3.12.7.2). Contact

stabilization time shall be measured on each contact set using an oscilloscope of other acceptable means approved

by the qualifying activity. The equipment shall have the capability of indicating a failure pulse width of greater than 1

�s. The trace shall show contact switching at operate and release, appropriate timing markers and maximum

allowable contact voltage drop markers (which equates to the allowable static contact resistance) when measured

using an oscilloscope. Rated voltage shall be applied to the coil. Contacts shall be loaded with 50 mV dc maximum

or peak ac at 50 mA maximum. Contact stabilization time shall be defined as the maximum time allowed for the

contacts to reach and maintain a static contact resistance state following the actual operate or release time of the

relay (essentially, it is the sum of the contact bounce time and the time for the dynamic contact resistance to stabilize

to the static contact resistance). After high level rated load life and intermediate current tests, the contacts shall be

loaded at 100 mA at 28 V dc maximum, and test voltage and contact bounce in lieu of contact stabilization time shall

be measured as specified in 4.8.7.7.1.