TEE Transducers
HD11 XE Getting Started
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Current i, driven by line supply e, flows through all stray capacitances between the
primary wiring and the ultrasound system’s metal chassis. Ordinarily, current then
flows from the metal chassis through S3 and back to e through a third-wire
ground. When S3 is thrown in the other position, current i is forced:
1. From the chassis through the metal parts of the transducer
2. Through impedance Z, produced by the insulating layer that covers the metal
parts of the transducer and the saline solution
3. Through the test electrode
Saline generally presents an impedance of about 500 Ω, so Z will vary between
850 kΩ and 500 Ω, depending on whether or not there is a conductive pathway
caused by a hole in the transducer’s insulating layer.
NOTE
Do not make a DC measurement of impedance. This could set up a voltaic cell,
with the metal of the transducer and a test electrode in the salt bath forming the
two electrodes and an electrolyte. Such a voltaic cell produces inaccurate resis-
tance measurements.
Equipment and Procedure
You need the following equipment to perform the electrical safety check proce-
dure:
• Dempsey 432HD or 232D safety analyzer or equivalent
•Philips 21110A Disinfection Basin or equivalent
• Saline solution (9 grams (0.3 oz) of salt to 1 liter (1 qt) of tap water) or one of
the tested disinfectants listed in this section
➤ To p e r f o r m t h e e l e c t r i c a l safety check procedure
1. Gather the equipment in the preceding list.
2. Fill the basin to the fill line with saline solution.
L Line mains supply
N Neutral mains supply
E Earth Ground
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