Kikusui 149-10A Operation Manual page 17

If the 149-10A is grounded in Fig.3.4, terminals A and B of the
measured object are shorted through the ground and the measured
object is adversely affected. As such, if the low voltage side (GND
side) of the measured object is unknown, determine it by following
the procedure below, and connect properly.
■ How to determine the polarity of the measured object
As shown in Fig. 3.5, connect a high voltage test lead to terminal A
or B, and assume the side with the higher voltage reading to be the
high voltage side.
149-10A
High voltage test lead
Fig. 3.5 Polarity check
149-10A
Ground
A B
Measured
object
15