Specifications | AN103C |
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Specifications | AN103C |
Business section |
Specifications | AN103C |
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Content | Application Note AN103C www.hamlin.com © 2007 Hamlin Electronics L. P. p 3/4 enough that the reed switch has time to react. Also, coil inductance can cause the current to lag behind the applied voltage and result in offset errors. Hamlin’s standard for ramp rate is 100 AT/s although slower or somewhat faster will also work. A manual ramp of a power supply, preferably in current drive mode, can be done, but accuracy will be limited by the precision at which an operator reacts to the contact closure. 4. Apply an additional drive level to the coil to measure the contact resistance. Hamlin’s standard value to add is 10 AT. Allow the coil drive and switch to settle for a small amount of time, such as 10 ms, after applying this additional coil drive. Then measure the contact resistance using a 4-wire Kelvin connection. Hamlin uses contact spacing of 25.4 mm (1 inch) as a standard. 5. Linearly decrease (ramp) the coil current as in step 3 until the reed switch opens. As in step 3, measure the coil current and multiply by the number of turns to determine the Drop- Out of the switch. Then set the coil supply to zero. Test Procedure Chart Test Sequence Control One of the difficulties in accurately measuring Pull-In and Drop-Out is determining the coil current at the time that the reed switch closes and opens. There are several methods that may be employed to do this. In all cases, Pull-In and Drop-Out are found by multiplying the current at closure or opening by the number of turns in the test coil. Also, in all cases, Drop-Out is determined by reversing the direction of coil ramp (decreasing vs. increasing) and monitoring for the reversed switch state (opening vs. closure). 0 20 40 60 80 100 .00.04cc+.02o -closure of switch -opening of switch slo pe=100 AT/s (not to scale) Coil Drive in Ampere-turn [AT] Time in second [s] Recommended Test Sequence (Coil Drive Waveform) |
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Following Datasheets | AN104 (2 pages) AN105A-Tech-Extended_Temperature_Operation (6 pages) AN107-Capacitive_Loads (1 pages) AN110A-Tech-Reed_Switch_Selector_Guide (3 pages) AN111A-Tech-Shock (1 pages) AN113A-Tech-Vibration (1 pages) AN115-Tech-Soldering_Temperatures (1 pages) AN121-Storage (1 pages) an605cn (4 pages) an608-cn (6 pages) |
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