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| 1, Dome Trip Force Measurement |
| Equipment Used |
Test Stand: Chatillon model LTC with fine feed platform.
Force Gauge: IMADA linear spring type, 0-1000 grams, with 5 gram divisions, model PS1.
Test Point: 3.0mm (0.12") diameter with flat bottom.
Height Gauge: 0.001-600mm, with 0.001 mm devisions |
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| Setup |
| Position the center of the metal dome to be tested within .010" of the test point center of Trip/Rebound Force Tester. The test point must be perpendicular to the dome. The dome must be on a hard flat surface, and needs to be vented to avoid air entrapment. Air trapped under the dome will increase the trip force and give a false reading. |
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| Measuring |
- Precondition the dome with 10 actuations
- Gradually apply pressure to the dome until it trips and record the reading. This reading is the "trip force".
- Gradually release the pressure from the metal dome until it snaps back. If desired record the reading. This reading is the release force. (Release force is the result of dome geometry and is sometimes useful in identifying dome characteristics.)
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2, Dome Life Testing |
Setup |
Metal Domes are tested on a hard flat surface perpendicular to the actuator of Dome Life Tester. The actuator must be in the center of the dome. The dome is attached by a means of plastic tape using pressure sensitive adhesive and providing for venting of the dome. |
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| Testing |
| Life testing is performed in accordance with ASTM F1578-98 (Standard practice for contact closure cycling of a membrane switch), less electrical resistance testing. The test is run continuously at approximately 3-12 cycles per second, using either a .188" or .625" diameter full radius silicon plunger which is about 45 durometer hardness. Actuation load should not exceed the dome trip force by more than 300 grams. The close-to-open ratio should be approximately 50%. |
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| Failure |
| We consider a metal dome or dome arrays to have failed when it no longer exhibits a crisp tactile feedback or has dropped significantly in trip force. |
