Performing a “Doble test” on something is really just slang in the electrical engineering world. This test, which measures how much power is being delivered to the insulation surrounding any particular wire, can be performed by many different devices. However, because the manufacturer Doble makes the best test equipment rentals there are, these tests have now been given the manufacturer’s name by many.
When using Doble testing, a 2.5 kV or 10 kV signal is directed towards the wire so that it can measure the current flow being delivered into the wire. The equipment does this using both the wattage and the VA of the specimen being tested, and uses each to determine how much power is available. Some testing devices will automatically calculate how much power is being delivered, while with others the user must calculate that for themselves.
When reading a Doble, you obviously must know what you’re looking for. It’s important to understand that the lower the reading, the better it is as it means that there is no debris, excess liquid, or anything else degrading and corroding the wires. 1% or lower is typically what people are looking to see on the tester but things like temperature and other factors can throw off the reading. This is why it’s so important to make the necessary adjustments and be very specific with calculations – to make sure that when you test, you get the right results!