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1/4 W Resistor Kit: Carbon Film Resistors Rated and Colour-Coded to MIL-PRF-22684 Style RL07
A 1/4 W rating is earned, not printed: the US military resistor specification gives its RL07 style 1/4 W at 70 °C only if the resistors survive its tests. Carbon film resistors in a range of values are checked, overloaded for 5 seconds, run for 1,000 hours at 70 °C on a sample, colour-coded with five bands and sorted into a kit.
Result: an assortment of 1/4 W carbon film resistors, ±5 % or ±2 %, each band-coded with its value.
Source: MIL-PRF-22684F, Resistors, Fixed, Film (Insulated) (US Department of Defense, 2006), style RL07. Not given here: the RL07 body and lead sizes and the allowed change in the life test, which are in the RL07 detail sheet. Unknown: the band paint; only its colours are fixed. Picture: Wikimedia Commons.
Kati
6 weeks
Maagizo
1
1
Check each value
Check each value
Measure the dc resistance of every resistor. It must lie within its tolerance of the nominal value: ±5 % or ±2 %. Work out its rated working voltage from E = √(P × R) with P = 1/4 W, but never above 250 V: for example 50 V for 10 kΩ, 9.1 V for 330 Ω. Ours: a Wheatstone bridge.
Vifaa kwa hatua hii:
Kipingamizi cha utando wa kaboni1 assorted values, as many of each as the kit needsZana zinazohitajika:
Daraja la Wheatstone2
2
Overload for 5 seconds
Overload for 5 seconds
Mount a resistor horizontally in still air, nothing within 3 in. of it except the base 2 in. below. Apply 2.5 times its rated working voltage (but not more than 500 V) for 5 seconds. Measure again 30 to 35 minutes later: the change may not exceed ±(0.5 % + 0.05 Ω), with no arcing, burning or charring.
Zana zinazohitajika:
Chanzo cha nishati ya mkondo wa moja kwa moja
Saa ya kupima mudaDaraja la Wheatstone3
3
Run the life test on samples
Run the life test on samples
Solder sample resistors from the batch to lightweight terminals with 1 in. of lead, spaced so none warms another, in still air at 70 °C (+15, -5). Measure them first, then apply the rated working voltage 1 1/2 hours on and 1/2 hour off for 1,000 hours, measuring at the end of an off period after 250, 500 and 1,000 hours. A batch whose samples pass carries the 1/4 W rating. Not given here: the allowed change, which the RL07 detail sheet sets. Ours: an oven as the 70 °C chamber.
Zana zinazohitajika:
Oveni
KipimajotoChanzo cha nishati ya mkondo wa moja kwa moja
Chuma cha kulehemia
Waya wa LehemuDaraja la Wheatstone4
4
Paint the colour bands
Paint the colour bands
On a body of any colour but black (tan is preferred), paint five bands: first figure, second figure, multiplier (black 1, brown 10, red 100 ... blue 1,000,000; gold 0.1, silver 0.01), tolerance (gold ±5 %, red ±2 %), and a wider white band, about 1 1/2 times the others, for solderable leads. Figures: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. So 330 Ω ±5 % is orange, orange, brown, gold, white. Unknown: the paint; the colours must be permanent and nonfading.
Vifaa kwa hatua hii:
Rangi ya kuweka alama za mikanda ya rangi1 set of coloursZana zinazohitajika:
Brashi zenye ncha nyembamba5
5
Sort into the kit
Sort into the kit
Sort the rated, coded resistors by value into the compartments of a box, one value to a compartment.
Zana zinazohitajika:
Sanduku la kupanga vipande vya mchezoVifaa
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- 1 set of coloursKishikilia Nafasi
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CC0 Umma Wote
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Saidia Mtengenezaji kwa kununua bidhaa kupitia Mchoro wao ambapo wanapata Kamisheni ya Mtengenezaji iliyowekwa na Wachuuzi, au unda marudio mapya ya Mchoro huu na uiunganishe kama kiungo katika Mchoro wako kuchangia mapato.