ASTM B539-02 pdf free

04-15-2021 comment

ASTM B539-02 pdf free.Standard Test Methods for Measuring Resistance of Electrical Connections (Static Contacts).
This procedure eliminates the effects of thermal po-tentials from the measurement and compensates for lack ofprecision in zeroing the test instruments.
Test Method A,Standard Test Current——Discontinued asa test method.
Test Method B,Rated Current ‘Testing:Table 1 is an example of currents used in rated currenttests of static contacts and connectors. Rated currents are
specified by vendor or user and are generally large enough toheat the test samples.Consequently, measured resistances maybe different from those obtained with Test Method C.Report in detail the conditions under which ratedcurrent measurements are made. The size of the parts,leadlengths, mounting provisions, ambient temperature, and venti-lation of the test position will affect the temperature at whichthe test specimens stabilize,as well as the time required toreach a stable temperature.Read the resistances when the temperature of the testspecimen has stabilized with current flowing. Determine thetime for stabilization by taking a series of readings of resis-tance or temperature as the test specimen warms. When thetemperature stabilizes the readings will become constant.Record the time required,and allow this time before eachmeasurement on similar test specimens.Measure the resistance using a suitable dc or acmethod.The dc method with current reversal given in 9.3 issuitable, however,current reversal may be unnecessary if thevoltage drop is large compared with thermal potentials. The primary requirement for dry circuit testing ofcontacts is that the voltage and current applied to the test
specimens must never be allowed to exceed certain maximumlimits. These limits are: 20 mV (0.020 V) and 100 mA (0.100 A). To assure these limits,use a power supply circuit thatprovides 20-mV opencircuit voltage and 100 mA short circuitcurrent.
Maintain the above maximum limits on test voltageand current. Avoid transient voltage pulses due to switching apower supply on or off, since it is known that pulses as short as0.1 us can cause oxide film breakdown and thereby invalidatea dry circuit test.An output resistance for the power supply of0.2 Q is implied by these specifications. Avoid the use of asupply with higher than 0.2 Q to obtain a test current of 100mA,since a momentary loss of contact in a test specimenwould apply a voltage greater than 20 mv to the test specimen5.ASTM B539 pdf download.

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