02-10-2015, 12:03 PM
1. Go with whatever the cheapes one you find, a metal film 5% is just fine.
2. No need for flame proof. If you get flames, you got worse problems, and adequately power rated resistor is all you need.
3. Calculate the wattage by U-square over R rule, you should know the dropout across the resistor. I use 1W for everything above 50K indiscriminately and for lower values I calculate the wattage.
4. It is rarely you need a resistor of 3.3M value to be very accurate. 10-20% is likely OK. However in Mouser there is plenty of 3.3M axials and one from Vishay 1/2W (which is plenty) is 13 cents stock.
2. No need for flame proof. If you get flames, you got worse problems, and adequately power rated resistor is all you need.
3. Calculate the wattage by U-square over R rule, you should know the dropout across the resistor. I use 1W for everything above 50K indiscriminately and for lower values I calculate the wattage.
4. It is rarely you need a resistor of 3.3M value to be very accurate. 10-20% is likely OK. However in Mouser there is plenty of 3.3M axials and one from Vishay 1/2W (which is plenty) is 13 cents stock.
