Exact meaning of 'tolerance'

[ants]

I'm wanting to know how tolerance works exactly.

For example I have a resistor that has a value of 1K +/-5% and measures at 990 ohms. Does tolerance mean the resistance will stay permanently at 990 ohms or vary between 950 and 1050?

Thanks.

 

[JoannesPaulus]

it will stay at 990.

 

[IanP]

The value can be anywhere between 990-5% and 990+5% but will not vary (in practice it will vary, as every component does, but very little with, for example, temperature) ..

For example, if you measure a real resistor and it’s resistance is 965Ω – it still belongs to 990Ω-/+5%, but the value stays at 965 – that’s it ..

IanP

 

[flatulent]

You have to read the data sheet carefully. Some of them will tell you that over time and temperature the resistance will not vary outside that range.

 

[keith1200rs]

The value can be anywhere between 990-5% and 990+5% but will not vary (in practice it will vary, as every component does, but very little with, for example, temperature) ..

For example, if you measure a real resistor and it’s resistance is 965Ω – it still belongs to 990Ω-/+5%, but the value stays at 965 – that’s it ..

IanP

990 ohms is the value measured. The nominal value was 1k. So the expected range is 1k+5% to 1k-5% not 990+5% to 990-5%.

Keith

 

[IanP]

The value can be anywhere between 990-5% and 990+5% but will not vary (in practice it will vary, as every component does, but very little with, for example, temperature) ..

For example, if you measure a real resistor and it’s resistance is 965Ω – it still belongs to 990Ω-/+5%, but the value stays at 965 – that’s it ..

IanP

990 ohms is the value measured. The nominal value was 1k. So the expected range is 1k+5% to 1k-5% not 990+5% to 990-5%.

Keith

Of course you're right, somehow missed that 1k ..
In other word, it says at 990 ..