Insulation resistance measurement apparatus and method thereof

An insulation resistance measurement apparatus comprising:

• a first resistance unit having a first end connected to a positive side of a battery and a second end connected to a ground, wherein the first resistance unit is variably controllable between having a first resistance value or a second resistance value greater than the first resistance value;
• a second resistance unit having a first end connected to a negative side of the battery and a second end connected to the ground, wherein the second resistance unit is variably controllable between having a third resistance value or a fourth resistance value greater than the third resistance value;
• a voltage measurement unit configured to measure a voltage across the first resistance unit and a voltage across the second resistance unit;
• and
• an insulation resistance calculation unit configured to calculate a first insulation resistance value between the positive side of the battery and the ground and a second insulation resistance value between the negative side of the battery and the ground based on the first resistance value, the second resistance value, the third resistance value, the fourth resistance value and the voltage measured by the voltage measurement unit wherein the insulation resistance calculation unit has a first insulation resistance measurement mode and a second insulation resistance measurement mode, wherein the first insulation resistance measurement mode has a lower error rate than the second insulation resistance measurement mode in a first measurement range, and wherein the second insulation resistance measurement mode has a lower error rate than the first insulation resistance measurement mode in a second measurement range.