Fukuda Denshi VaSera VS-1500, Service Manual

Page: 83 / 216

Chapter 5 Maintenance
Confidential Copying Prohibited
5-51
5.9.5 Safety Inspections
Safety-related testing methods and measurement equipment are prescribed in safety test
standards. At the actual sites where medical treatment is being given, however, it can be
extremely difficult to verify that everything meets the standards. For this reason, when
performing inspections, set up and make acceptance determinations using the methods
described below.
WARNING
If, during a safety inspection, a value that exceeds the allowable limit is confirmed,
immediately stop using the given unit; then replace the defective part or make proper
repairs. Failure to repair the unit can lead to a serious accident.
●
Before checking the leakage current
There are a number of conditions for measuring leak current. For the measured values,
however, use the maximum values that are obtained.
When checking, it is also important to make comparisons with past measured values to
confirm that there are no large differences.
To measure the leakage current, use leakage current gauges (electronic voltmeters and
digital voltmeters), impedance for measurement, power switch box, and similar equipment.
●
Impedance for measurement
The impedance will have a structure such as that shown below.
By measuring the voltage at both ends of the impedance, you can find the leakage current.
●
Voltmeter
Because digital voltmeters are required to indicate true effective values for composite
waveform from DC to 1 MHz, it is recommended that you use a voltmeter whose
performance meets the prescribed standard as closely as possible.
For use during maintenance and inspection in the field, you can use a commercially
available digital voltmeter instead. However, check the frequency band of the voltmeter you
plan to use ahead of time. To measure a leakage current that exceeds the measurable
frequency band, use it with care paying attention to the indication on the voltmeter.
●
Electric current calculation method
When checking a leakage current, measure the AC voltage by using a leakage current
measuring device (MD).
Convert the measured voltage to current by employing the formula below.
If the phase is switched and measurements are made, use the higher voltage to calculate
the current.
Measured voltage (V)
1000
= Measured current (mA)