Junior Member level 3
I mean when i adjust a ratio, whatever if it wasn't the exact ratio i need, i should stay as it is. Let's say 1% drift in ratio. Is multiturn trimpots enough for that? Or should i find 1% resistors? metal film? os sth else?
It's a possible behaviour. But the assumption, that both resistors have equal actual TC values is just a speculation. A standard 1% metal film resistor may be specified with a maximum TC of +/- ppm/K. But how about the actual TC of individual resistors? There is a certain chance, that smae value, same production lot resistors have a similar actual TC, but it's not guaranteed. This is only different for the said voltage divider parts, or resistor array with a specified TC tracking.I read that in a voltage divider that made of fixed resistors, the bigger resistance dissipate more power and get warmer. And if the temp drift is proportional to temperature, its value change more. Lets say if the cooler one have a resistance 1.1Ra then the warmer resistor will be 1.2Rb. Is that right?
I guess, you won't find any TC or even TC tracking specification for 10% (most likely carbon film) resistors. But that doesn't mean, that they must be particular bad.Then i connected one 100R and one 1k2 standart 10% resistors in series to same supply and measure midpoint as 4,66V. Then waited 10minutes, no drift. Then put hot glue and it was still constant at 4,66V.