MIL-STD-202H.pdf - 第272页

MIL-STD-202-308

FIGURE 1. Block diagram of system.

4.2. Procedure.

4.2.1 Operating conditions. The test shall be performed at an ambient temperature of 25°C ±2°C, unless otherwise

specified. The specimen under test shall be stabilized at room ambient temperature prior to test. No special

preparations of the specimen are required other than that its leads be clean. Standard operating conditions, based

on the resistance value of the specimen to be tested, are given in table 1. The values of the isolation resistor, Rm,

and the dc voltage, V, should be observed, although they are not critical, because the index is reasonably

independent of the values of the isolation resistor and the dc voltage over a broad range. Therefore, it is not

necessary to obtain the exact value of dc voltage given in table 1, rather to set it near the value, and to read carefully

and record its value at the time of the measurement. In no case shall the ratings of the resistor under test be

exceeded.

4.2.2 Measurements. After the operating conditions have been established, the measurement operation shall be

performed in three steps, as follows:

(1) Calibration (see 4.2.2.1).

(2) Measurement of system noise (see 4.2.2.2).

(3) Simultaneous measurement of the dc voltage and the resulting total noise (see 4.2.2.3).

Generally, the measurements should be made in the order listed. The precautions in 1.2 should be observed.

4.2.2.1 Calibration. The calibration technique (see 4.1.1.3) standardizes the gain of the ac system for the particular

resistor under test. For the noise measurements in steps 2 and 3 which follow, the sum of the ac attenuator setting

and the ac meter reading, in dB, is a direct indication of the noise present in terms of an "open-circuit" rms noise

voltage appearing across the terminals of the resistor under test.

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MIL-STD-202-308

TABLE 1. Standard operating conditions.

| | | |

| Resistance | Resistors 1/2 watt and higher | Resistors 1/4, 1/8, and 1/10 watt |

| | | | | | | | |

| test (Rt) | (Rm) | | | (Pdc) | | | (Pdc) |

| | | | | | | | |

| | | | | | | | |

| 100 | 1,000 | 10.1 | 3.2 | 100 | 10.1 | 3.2 | 100 |

| 120 | 1,000 | 11.6 | 3.8 | 120 | 10.9 | 3.5 | 100 |

| 150 | 1,000 | 13.5 | 4.7 | 150 | 11.8 | 3.9 | 100 |

| 180 | 1,000 | 15.1 | 5.7 | 180 | 12.5 | 4.2 | 100 |

| 220 | 1,000 | 16.9 | 7.0 | 220 | 13.4 | 4.7 | 100 |

| 270 | 1,000 | 18.3 | 8.2 | 250 | 14.3 | 5.2 | 100 |

| 330 | 1,000 | 19.2 | 9.7 | 250 | 15.1 | 5.7 | 100 |

| 390 | 1,000 | 19.9 | 9.9 | 250 | 15.8 | 6.2 | 100 |

| 470 | 1,000 | 20.7 | 10.8 | 250 | 16.7 | 6.9 | 100 |

| 560 | 1,000 | 21.4 | 11.8 | 250 | 17.5 | 7.5 | 100 |

| 680 | 1,000 | 22.3 | 13.0 | 250 | 18.3 | 8.2 | 100 |

| 820 | 1,000 | 23.1 | 14.3 | 250 | 19.2 | 9.1 | 100 |

| | | | | | | | |

| 1,000 | 1,000 | 24.0 | 15.8 | 250 | 20.0 | 10.0 | 100 |

| 1,200 | 1,000 | 24.8 | 17.3 | 250 | 20.8 | 11.0 | 100 |

| 1,500 | 1,000 | 25.8 | 19.4 | 250 | 21.7 | 12.2 | 100 |

| 1,800 | 1,000 | 26.6 | 21.2 | 250 | 22.5 | 13.4 | 100 |

| 2,200 | 1,000 | 27.4 | 23.4 | 250 | 23.4 | 14.8 | 100 |

| 2,700 | 10,000 | 28.3 | 26.0 | 250 | 24.3 | 16.4 | 100 |

| 3,300 | 10,000 | 29.2 | 28.7 | 250 | 25.2 | 18.2 | 100 |

| 3,900 | 10,000 | 29.9 | 31.2 | 250 | 25.9 | 19.7 | 100 |

| 4,700 | 10,000 | 30.8 | 34.3 | 250 | 26.7 | 21.7 | 100 |

| 5,600 | 10,000 | 31.5 | 37.4 | 250 | 27.5 | 23.7 | 100 |

| 6,800 | 10,000 | 32.3 | 41.2 | 250 | 28.3 | 26.1 | 100 |

| 8,200 | 10,000 | 33.2 | 45.3 | 250 | 29.1 | 28.6 | 100 |

| | | | | | | | |

| 10,000 | 10,000 | 34.0 | 50.0 | 250 | 30.1 | 32.0 | 100 |

| 12,000 | 10,000 | 34.8 | 54.8 | 250 | 30.9 | 35.0 | 100 |

| 15,000 | 10,000 | 35.8 | 61.2 | 250 | 31.8 | 39.0 | 100 |

| 18,000 | 10,000 | 36.6 | 67.1 | 250 | 32.5 | 42.0 | 100 |

| 22,000 | 10,000 | 37.4 | 74.2 | 250 | 33.4 | 47.0 | 100 |

| 27,000 | 0.10 mego | 38.3 | 82.2 | 250 | 34.3 | 52.0 | 100 |

| 33,000 | 0.10 mego | 39.2 | 90.8 | 250 | 35.1 | 57.0 | 100 |

| 39,000 | 0.10 mego | 40.0 | 98.7 | 250 | 35.8 | 62.0 | 100 |

| 47,000 | 0.10 mego | 40.7 | 108 | 250 | 36.7 | 69.0 | 100 |

| 56,000 | 0.10 mego | 41.5 | 118 | 250 | 37.5 | 75.0 | 100 |

| 68,000 | 0.10 mego | 42.3 | 130 | 250 | 38.3 | 82.0 | 100 |

| 82,000 | 0.10 mego | 43.1 | 143 | 250 | 39.2 | 91.0 | 100 |

See footnote at end of table.

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联系方式：xuyj@beice-sh.com 13917165676

MIL-STD-202-308

TABLE 1. Standard operating conditions - Continued.

| | | |

| Resistance | Resistors 1/2 watt and higher | Resistors 1/4, 1/8, and 1/10 watt |

| | | | | | | | |

| test (Rt) | (Rm) | | | (Pdc) | | | (Pdc) |

| | | | | | | | |

| | | | | | | | |

| 0.10 mego | 0.10 mego | 44.0 | 158 | 250 | 40.0 | 100 | 100 |

| 0.12 mego | 0.10 mego | 44.8 | 173 | 250 | 40.8 | 110 | 100 |

| 0.15 mego | 0.10 mego | 45.8 | 194 | 250 | 41.7 | 122 | 100 |

| 0.18 mego | 0.10 mego | 46.5 | 212 | 250 | 42.5 | 134 | 100 |

| 0.22 mego | 0.10 mego | 47.5 | 234 | 250 | 43.4 | 148 | 100 |

| 0.27 mego | 1.0 mego | 38.6 | 85.0 | 26.8 | 38.6 | 85.0 | 26.8 |

| 0.33 mego | 1.0 mego | 40.0 | 99.0 | 29.7 | 40.0 | 99.0 | 29.7 |

| 0.39 mego | 1.0 mego | 41.0 | 112 | 32.2 | 41.0 | 112 | 32.2 |

| 0.47 mego | 1.0 mego | 42.1 | 127 | 34.3 | 42.1 | 127 | 34.3 |

| 0.56 mego | 1.0 mego | 43.1 | 143 | 36.5 | 43.1 | 143 | 36.5 |

| 0.68 mego | 1.0 mego | 44.2 | 161 | 38.1 | 44.2 | 161 | 38.1 |

| 0.82 mego | 1.0 mego | 45.1 | 180 | 39.5 | 45.1 | 180 | 39.5 |

| | | | | | | | |

| 1.0 mego | 1.0 mego | 46.0 | 200 | 40.0 | 46.0 | 200 | 40.0 |

| 1.2 mego | 1.0 mego | 46.8 | 218 | 39.6 | 46.8 | 218 | 39.6 |

| 1.5 mego | 1.0 mego | 47.6 | 240 | 38.4 | 47.6 | 240 | 38.4 |

| 1.8 mego | 1.0 mego | 48.0 | 250 | 34.7 | 48.0 | 250 | 34.7 |

| 2.2 mego | 1.0 mego | 48.0 | 250 | 28.4 | 48.0 | 250 | 28.4 |

| 2.7 mego | 1.0 mego | 48.0 | 250 | 23.2 | 48.0 | 250 | 23.2 |

| 3.3 mego | 1.0 mego | 48.0 | 250 | 18.9 | 48.0 | 250 | 18.9 |

| 3.9 mego | 1.0 mego | 48.0 | 250 | 16.0 | 48.0 | 250 | 16.0 |

| 4.7 mego | 1.0 mego | 48.0 | 250 | 13.3 | 48.0 | 250 | 13.3 |

| 5.6 mego | 1.0 mego | 48.0 | 250 | 11.2 | 48.0 | 250 | 11.2 |

| 6.8 mego | 1.0 mego | 48.0 | 250 | 9.2 | 48.0 | 250 | 9.2 |

| 8.2 mego | 1.0 mego | 48.0 | 250 | 7.6 | 48.0 | 250 | 7.6 |

| | | | | | | | |

| 10 mego | 1.0 mego | 48.0 | 250 | 6.2 | 48.0 | 250 | 6.2 |

| 12 mego | 1.0 mego | 48.0 | 250 | 5.2 | 48.0 | 250 | 5.2 |

| 15 mego | 1.0 mego | 48.0 | 250 | 4.2 | 48.0 | 250 | 4.2 |

| 18 mego | 1.0 mego | 48.0 | 250 | 3.5 | 48.0 | 250 | 3.5 |

| 22 mego | 1.0 mego | 48.0 | 250 | 2.8 | 48.0 | 250 | 2.8 |

1/ DC voltage across the resistors under test for the measurement of total noise.

4.2.2.2 System noise (S). System noise is the background noise present when direct current is not present in the

resistor under test. System noise is indicated after turning off the calibration voltage. The algebraic sum of the ac

attenuator setting and the ac meter reading gives the magnitude of system noise, S, in dB.

4.2.2.3 Total noise (T). Both the dc voltage and the total noise are measured simultaneously. The value of dc

voltage is given in table 1. The application of excessive dc voltage should be avoided by setting the dc voltage

control to its minimum before applying the voltage, and when the voltage is applied, it should be increased to the

desired value. The magnitude of the dc voltage is given by the sum, D, of the dc attenuator setting and the dc meter

reading in dB. D equals 20 log V, where V is the dc voltage, in volts, applied to the terminals of the resistor under

test. The associated noise measurement indicates the total noise present, i.e., the quadratic sum of the system noise

and the current noise. This total noise is indicated by T, in dB.

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联系方式：xuyj@beice-sh.com 13917165676