Test device

A test device 10 includes: a power source 12, such as a rechargeable battery, having first and second connection points 14, 16; a first voltmeter 18 having first and second inputs 20, 22; a second voltmeter 24 having first and second inputs 26, 28; first, second and third ports 30, 32, 34; and a user interface 108. The first port 30 is coupled to the first connection point 14 of the power source and the first input 20 of the first voltmeter 18. The second port 32 is coupled to the second input 22 of the first voltmeter, the first input 26 of the second voltmeter 24, and the second connection point 16 of the power source. The third port 34 is coupled to the second input 28 of the second voltmeter 24. The user interface shows a first voltage between the first and second ports and a second voltage between the third and second ports. The tester may provide a voltage to an otherwise unpowered circuit under test e.g. on a vehicle.