Philips M2540 - page 57

M2540-92000-01 A M2540 Ultrasound System Field Service Manual Page 57
Theory of Operation: Transducer Safety Testing: Test Setup and Theory
Imposing an open neutral condition prevents all system current from flowing. This creates a
higher potential for leakage current Ichassis. Most flows safely through the ground wire; some
flows through the transducer. This Itransducer is still fairly low, unless the chassis is not properly
grounded.
Figure 4-8 Ground Wire Leakage Test Diagram (for Comparison with 1st Single Fault
Condition)
With the transducer circuit disconnected, all of the leakage current Ichassis flows through the
analyzer by way of the ground wire.
In the 1st single fault condition transducer leakage test (Figure 4-6 on page 56), all the leakage
current Ichassis flows through the analyzer by way of the transducer. In that condition, only the
resistance or impedance of the respective paths varies.
•If the transducer sheath is intact, its resistance is high, and Imeasured in the transducer leakage
test is low when compared with Imeasured in the ground wire leakage test.
A
I
7ASW030-5
Hot
Neutral
Ground
I
C
I
I
measured
system
chassis
transducer
S
Z