MIL-STD-202G
METHOD 304
RESISTANCE-TEMPERATURE CHARACTERISTIC
1.PURPOSE. It is the purpose of this test to determine the percentage change in direct-current (dc) ohmic resistance from the dc ohmic resistance at the reference temperature, per unit temperature difference between the test temperature and the reference temperature. The equation (see 3) used to calculate this characteristic, commonly called the "temperature coefficient of resistance", is based on an assumed straight-line relationship between resistance and temperature over a range of specified test temperatures.
2.PROCEDURE.
2.1Preparation. Test leads used to connect the specimens to the resistance-measuring devices shall be firmly fastened to the specimens. Precautions shall be taken to minimize errors in resistance measurement due to such factors as lead resistance, spurious electromotive forces, condensation of moisture, etc., throughout the range of test temperatures, by utilization of suitable test-lead materials and measurement techniques or by applying appropriate corrections.
2.2Test temperatures. The reference temperature shall be 25°C or as specified. There shall be two standard series of test temperatures. The first series shall be 25°, 0°, -15°, and -55°C; the second series shall be 25°, 50°, 75°, 100°, 125°, 200°, 275°, and 350°C. The tolerance on eachtemperature in both series shall be ±3°C. The lowest test temperature in the first series, and the highest test temperature in the second series, shall be as specified. Measurements for each series of temperatures shall be performed in the order shown without interruption.
However, a lapse of time not to exceed 24 hours is permitted between the end of the first series and the start of the second series.
2.3Measurements. The resistance of each specimen shall be measured 30 to 45 minutes after the chamber temperature has become stable to within ±0.5°C at a test temperature. However, it will be permissible to measure the resistance before the end of this period if the resistance has become stable to within ±0.1 percent as determined by preliminary measurements made at 5 minute intervals after stabilization of the chamber temperature. Unless otherwise specified, the temperature at the time of measurement shall be measured to an accuracy of ±1 percent of the temperature difference between the nominal test temperature and the nominal reference temperature +0.5°C. Resistance measurements shall be made in accordance with method 303 of this standard.
3. RESULTS. The resistance-temperature characteristic, in percent change in resistance per degree centigrade, at each test temperature shall be computed as follows:
Resistance - temperature characteristic = |
R2 |
- R1 |
X 100 |
|
|
R1 ( t2 - t1 )
Where:
R1 = resistance at reference temperature (in same series as test temperature) in ohms. R2 = resistance at test temperature in ohms.
t1 = reference temperature in degrees celsius. t2 = test temperature in degrees celsius.
4.SUMMARY. The following details are to be specified in the individual specification:
a.Reference temperature, if other than that specified (see 2.2).
b.Lowest and highest test temperature (see 2.2).
c.Accuracy of temperature measurement if other than that specified (see 2.3).
METHOD 304 24 October 1956
1 of 1
MIL-STD-202G
METHOD 305
CAPACITANCE
1.PURPOSE. The purpose of this test is to measure the capacitance of component parts. Preferred test frequencies for this measurement are 60 Hz, 120 Hz, 1 kHz, 100 kHz, and 1 MHz.
2.PROCEDURE. The capacitance of the specimen shall be measured at or referred to an ambient temperature of 25°C with a capacitance bridge or other suitable method at the frequency specified. The inherent accuracy of the measurement shall be ±(0.5 percent +0.2 picofarad) unless otherwise specified. Suitable measurement technique shall be used to minimize errors due to the connections between the measuring apparatus and the specimen. The alternating-current (ac) voltage actually impressed across the specimen shall be as low as practicable. When a direct-current (dc) polarizing voltage is required, it shall be as specified and shall exceed the peak ac voltage impressed across the specimen; however, the sum of the peak ac and the dc voltages shall not exceed the voltage rating of the specimen.
3.SUMMARY. The following details are to be specified in the individual specification:
a.Test frequency (see 2).
b.Limit of accuracy, if other than that specified (see 2).
c.Magnitude of polarizing voltage, if applicable (see 2).
d.Magnitude of AC rms test signal, if applicable (see 2).
METHOD 305 24 October 1956
1 of 1
MIL-STD-202G
METHOD 306
QUALITY FACTOR (Q)
1.PURPOSE. The purpose of this test is to measure the quality factor, commonly called Q, of electronic parts such as capacitors and inductors. By definition, the factor Q expresses the ratio of reactance to effective resistance of a circuit element. This numerical ratio is considered a "figure of merit" for a reactive component (or a resonant circuit utilizing such components) as it is a measure of the ability of the component (or circuit) to store energy compared to the energy it wastes. For this reason, Q is called "storage factor". Q is thus equal to the inverse of the dissipation factor. Relationship also exists between Q and the properties of a tuned circuit, such as the resonant rise in voltage phenomena. Each of the relationships involving Q mentioned above can be applied to the direct or indirect measurement of Q.
2.PROCEDURE. The quality factor or Q of the specimen shall be measured using a suitable instrument providing an accuracy of measurement within 10 percent of the specified value of Q. Measurements shall be made at the specified frequency. Suitable measurement techniques shall be used to minimize errors due to the connections between the measuring apparatus and the specimen.
3.SUMMARY. The following detail is to be specified in the individual specification: a. Test frequency (see 2).
METHOD 306 24 October 1956
1 of 1