Fluke Biomedical 07-487 - Manual (Page 7)

General Information
User Hints
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current be read as a voltage across an internal reference resistor. The mAs meter cannot be used with
these types. It must read the actual tube current with no other parallel path.
1.7 User Hints
The most common cause of drift in calibration to an x-ray generator is the change of the x-ray tube
filament emission. Because x-ray tubes and cables may arc on occasion, the high voltage transformer
has a high impedance that keeps these short circuit currents within safe limits. The regulation of the
transformer is often expressed as voltage drop per 100 mA of tube current. Large transformers regulate
about 4 kVp/100 mA and small transformers about 12 kVp/100 mA. The design of the generator circuit
compensates for the voltage drop: a large system exposing at 80 kVp at 500 mA would have an open
circuit voltage of 100 kVp. The regulation of the transformer drops the voltage to the correct value.
However, if the tube drifts to 350 mA, the regulation of the transformer will cause the tube voltage to rise
to 86 kVp. It is interesting to observe that films should be lighter from the reduced mA and darker from
the increased kVp. Actually, the real effect would be a change in the contrast scale of the radiograph and
would reduce the visibility of iodine contrast agents. The first indication would be reduced image contrast.
Whenever the kVp meter indicates poor calibration at high mA levels, it is probable that the tube filament
settings require adjustment. The mAs meter is used to check the filament settings by monitoring actual
mAs values of the exposures.
1.8 Receiving Inspection
Upon receipt of the instrument:
1. Inspect the carton(s) and contents for damage. If damage is evident, file a claim with the carrier and
contact Cardinal Health, Radiation Management Services at 440.248.9300.
2. Remove the contents from the packing material.
3. Verify that all items listed on the packing list have been received and are in good condition.
1.9 Storage
If the unit is to be stored prior to use, pack it in the original container, if possible, and store in an
environment free of corrosive materials, fluctuations in temperature and humidity, or vibration and shock.
1.10 Procedures, Warnings, and Cautions
The equipment described in this manual is intended to be used for QUALITY ASSURANCE testing of
diagnostic x-ray machines. It should be used only by persons who have been trained in the proper
interpretation of its readings and the appropriate safety procedures to be followed in the presence of
radiation and the high voltages associated with x-ray machines.
Although the equipment described in this manual is designed and manufactured in compliance with all
applicable safety standards, certain hazards are inherent in the use of this equipment.
WARNINGS and CAUTIONS are presented throughout this document, when applicable, to alert the user
to potentially hazardous situations. A WARNING is a precautionary message preceding an operation
which has the potential to cause personal injury or death. A CAUTION is a precautionary message
preceding an operation which has the potential to cause permanent damage to the equipment and/or loss
of data. Failure to comply with WARNINGS and CAUTIONS is at the user’s own risk and is sufficient
cause to terminate the warranty agreement between Cardinal Health, Radiation Management Services
and the customer.