When you apply a high voltage, greater than 100V, self-heating will occur in the multimeter´s internal signal-conditioning components. The additional error is proportional to the square of the voltage applied. These errors may be included in the multimeter´s specifications or listed as a separate adder. Temperature changes inside the multimeter due to self-heating may cause additional error on other ac voltage ranges. Once the voltage is removed the heat and the error will dissipate in a few minutes. As an example the 34401A´s specs above 300V and 1 A include self-heating errors. However, an additional error of 0.02% can occur on smaller voltages and currents until the heat dissipates.