A method comprising: configuring an isolation resistance measurement circuit in a first configuration at a first time instance; measuring a first voltage between a chassis of an electrical vehicle, EV, and a first node of a power system in the EV when the isolation resistance measurement circuit is in the first configuration, wherein the power system in the EV is a voltage source of the EV; configuring the isolation resistance measurement circuit in a second configuration at a second time instance; measuring a second voltage between the chassis and a second node of the power system when the isolation resistance measurement circuit is in the second configuration; determining a first isolation resistance between the first node of the power system and the chassis based on the first voltage, the second voltage, a voltage of the power system, and a resistance of a pole resistor; determining that the voltage of the power system changed from the first time instance to the second time instance; determining a first ratio between the first voltage and the voltage of the power system at the first time instance; scaling at least one of the first voltage or the voltage of the power system based on the first ratio when determining a second isolation resistance; determining the second isolation resistance between the second node of the power system and the chassis based on the first voltage, the second voltage, the voltage of the power system, and the resistance of the pole resistor, wherein at least one of the first voltage or the voltage of the power system used for determining the second isolation resistance is at least one of the scaled first voltage or the scaled voltage of the power system, respectively; determining that the first isolation resistance or the second isolation resistance is less than a threshold resistance; and outputting information based on the determination that the first isolation resistance or the second isolation resistance is less than the threshold resistance. configuring an isolation resistance measurement circuit in a first configuration at a first time instance; measuring a first voltage between a chassis of an electrical vehicle, EV, and a first node of a power system in the EV when the isolation resistance measurement circuit is in the first configuration, wherein the power system in the EV is a voltage source of the EV; configuring the isolation resistance measurement circuit in a second configuration at a second time instance; measuring a second voltage between the chassis and a second node of the power system when the isolation resistance measurement circuit is in the second configuration; determining a first isolation resistance between the first node of the power system and the chassis based on the first voltage, the second voltage, a voltage of the power system, and a resistance of a pole resistor; determining that the voltage of the power system changed from the first time instance to the second time instance; determining a first ratio between the first voltage and the voltage of the power system at the first time instance; scaling at least one of the first voltage or the voltage of the power system based on the first ratio when determining a second isolation resistance; determining the second isolation resistance between the second node of the power system and the chassis based on the first voltage, the second voltage, the voltage of the power system, and the resistance of the pole resistor, wherein at least one of the first voltage or the voltage of the power system used for determining the second isolation resistance is at least one of the scaled first voltage or the scaled voltage of the power system, respectively; determining that the first isolation resistance or the second isolation resistance is less than a threshold resistance; and outputting information based on the determination that the first isolation resistance or the second isolation resistance is less than the threshold resistance.