"When measuring voltages on hybrid vehicles, always use a DMM with minimum safety rating of CATIII 1000V," according to Steve White, president of Electronic Specialties. "In addition, your test leads should also be rated CATIII 1000V."
Such a meter, like Electronic Specialties' TMX-589, is specially built to handle such high voltage conditions that may exist on a hybrid vehicle. There are other meters that will boast the ability to hand 1,000V, but unless they are CATIII certified, it is best to use another tool.
What should we look out for?
"High voltage cables are normally colored orange," notes White. "Before taking any measurements, strictly follow OEM instructions and procedures regarding the disabling and verified shut-down of the vehicle's HV system."
The one special test you will need to know is an "insulation test," which requires a MegOhm meter sending a very high voltage pulse (as high as 1,000V on a Fluke 1577 and 1587.) One such example of this is the Electronic Specialties' Model 550. Some meters will act a lot like your DVOM but with an insulation test, such as the Fluke 1587, which has other standard meter functions, such as Min/Max.
This is how it works: Connect one meter lead on the ground for the HV cable/motor generator/etcetera and the other on the power side. Then, conduct the insulation test. Always follow OEM procedures and test using their specifications. The insulation test might be the only means you have to prove to the customer that their HV DTC can be repaired by a big money repair.
