* power dissipation - the maximum wattage rating depends upon the amount of heat which can be transferred to the surroundings w hile not exceeding the maximum element temperature. ambient air temperature, velocity of cooling air, thermal resistance of heat and the temperature of surrounding ob jects will affect this transfer, this must be taken into account when selecting a resistor. low resistance metal element resistors lob series ultra low resistance values (0.005 ? to 0.1 ? ) available in 1, 3 and 5 watt rated packages tolerances from ?% to ?% inherently non-inductive ( .02? at 0.5mhz) low temperature coefficient of resistance high stability over life dimensions (mm) type l max. d max. f min. d nom. c lob-1 9.9?.3 3.6?.2 38.1?.2 0.813?.05 33.27 lob-3 14.22?.25 5.33?.25 34.93?.18 0.81?.05 33.27 lob-5 23.37?.25 8.38?.25 31.75?.18 1.02?.05 42.42 general note welwyn components reserves the right to make changes in product specification without notice or liability. all information is subject to welwyn s own data and is considered accurate at time of going to print. ?welwyn components limited ?bedlington, northumberland ne22 7aa, uk telephone: +44 (0) 1670 822181 ?facsimile: +44 (0) 1670 829465 ?email: info@welwyn-tt.com ?website: www.welwyn-tt.com lob-1 lob-3 lob-5 continuous power dissipation at 25? in free air watts 1 3 5 overload power for 5 seconds watts 5 15 25 maximum working voltage volts 1xr 3xr 5xr maximum storage temperature c 175 175 175 electrical data physical data issue b ?03.02 a subsidiary of tt electronics plc welwyn components 104 l c d f d contact point contact point description lob ? series power precision metal element resistors feature resistance values down to 0.005 ? with virtually no inductance. available in 1, 3 and 5 watt rated axial leaded packages, these resistors are compatible with automatic insertion equipment. applications switchmode and linear power supplies. automotive current-sensing circuits. instrumentation. construction lob ? series resistors feature tinned copper leads welded directly to a low temperature coefficient resistance element in a highly automated proprietary process. the leaded resistor elements are then encapsulated in a moulding compound.
0 25 50 75 100 400 300 200 100 0 resistance (ohms x 10 -3 ) temperature coefficient of resistance (ppm/ c) low resistance metal element resistors lob series ? welwyn components limited bedlington, northumberland ne22 7aa, uk telephone: +44 (0) 1670 822181 facsimile: +44 (0) 1670 829465 email: info@welwyn-tt.com website: www.welwyn-tt.com 105 issue b 03.02 welwyn components % xam 202 dts-lim tset ? tinu *r % %1 801 dohtem )sruoh 0002( efil daol ? r % %1 701 dohtem kcohs lamreht ? r % %5.0 402 dohtem noitarbiv ? r % %5.0 312 dohtem kcohs lacinahcem ? r % %5.0 103 dohtem htgnerts cirtceleid ? r 01> 203 dohtem ecnatsiser noitalusni 11 ohms 0 25 50 75 100 125 150 175 100 90 80 70 60 50 40 30 20 10 0 ambient temp ( c) rated power (%) power derating percentage vs free air ambient temperature temperature coefficient of resistance vs resistance value *0.0005 ohm allowance for test/contact error. packaging resistors are supplied taped and reeled. bulk packaging available. ordering procedure example: lob3 at 10 milliohms and 5% tolerance on a reel of 1250 pieces - l o b 3 ? r 0 1 j i type value (use iec62 code) tolerance (use iec62 code) f 1% j 5% h 3% note: 1% & 5% preferred packing i tape lob1 3500/reel standard lob3 1250/reel lob5 800/reel
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