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Significance and Use
Changes in temperature and humidity during shipping, storage or use can affect the visual appearance, mechanical integrity, or electrical functionality of switches. This practice simulates three different environments to which membrane switches may be exposed.
The three industry-recognized switch categories based on performance levels are Level 1, Level 2, and Level 3 (see section 8.1).
Additionally, there may be custom requirements that vary by application, therefore, these requirements can be determined by customer and vendor agreement and be established as a Level 4.
This practice defines the duration of a single cycle. Multiple cycles may be appropriate depending on the requirements of the application.
1.1 This test method covers a procedure for temperature and humidity cycling of membrane switches.
1.2 This test method is performed to evaluate the properties of materials used in the construction of membrane switch assemblies as they are influenced by the absorption and diffusion of moisture and moisture vapor. This is an accelerated environmental test, accomplished by the continuous exposure of the test specimen to high relative humidity at an elevated temperature. Absorption of moisture by many materials results in swelling, which destroys their functional utility, causes loss of physical strength, and changes in other mechanical properties. Insulating materials which absorb moisture may suffer degradation of their electrical properties.
1.2.1 Physical changes:
18.104.22.168 Differential contraction or expansion rates or induced strain of dissimilar materials.
22.214.171.124. Cracking of surface coatings.
126.96.36.199 Leaking of sealed compartments.
188.8.131.52 Deformation or fracture of components.
1.2.2 Chemical changes:
184.108.40.206 Separation of constituents.
220.127.116.11 Failure of chemical agent protection.
1.2.3 Electrical changes:
18.104.22.168 Changes in electronic and electrical components.
22.214.171.124 Electronic or mechanical failures due to rapid water of condensate formation.
126.96.36.199 Excessive static electricity.
1.3 This test method is not intended to be a thermal shock procedure; a ramp rate between temperature extremes should not exceed 2°C/min.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
F1661 Test Method for Determining the Contact Bounce Time of a Membrane Switch
F1662 Test Method for Verifying the Specified Dielectric Withstand Voltage and Determining the Dielectric Breakdown Voltage of a Membrane Switch
F1663 Test Method for Determining the Capacitance of a Membrane Switch
F1680 Test Method for Determining Circuit Resistance of a Membrane Switch
F1689 Test Method for Determining the Insulation Resistance of a Membrane Switch
F2592 Test Method for Measuring the Force-Displacement of a Membrane Switch
ICS Number Code 31.220.20 (Switches)
UNSPSC Code 39122200(Electrical switches and accessories)