Fluke Biomedical 07-494 - Manual (Page 28)

Victoreen 07-494
Operators Manual
6-2
6.3 Performance Verification (Calibration Constancy)
In this section, two methods are described for verifying the accuracy of the kVp meter. Both methods
require a careful collection of installation data and periodic re-measurement of that data. The voltage
divider method is more direct than the multiple x-ray machine method. However, if at least five x-ray
machines are used in the multiple machine test, the results are very positive.
Voltage Divider Method
If available, an x-ray voltage divider should be used concurrently during the initial testing of the kVp
Meter.
1. Choose two x-ray machines suited for the test. It is recommended that different types of machines
be used (e.g., use one three phase machine and one single phase machine).
2. Make comparative measurements of the voltage divider and the kVp Meter.
3. If an oscilloscope is used to measure the voltage divider, use an independent voltmeter to measure
the scope sensitivity each time.
NOTE
Data with a kVp test cassette may be useful. Be
sure to note positioning error and film usage when
using the cassette.
4. Record all parameters of the measurement, including geometry, cable connections, tube ID,
generator ID, divider and kVp Meter waveform oscilloscope pictures, oscilloscope and voltmeter ID.
5. Periodically (every 6 months) or when a serious discrepancy occurs, repeat Steps 1 through 4 to
determine which piece of equipment is in error.
If two dissimilar x-ray machines are used, the
possibility of a systematic error is reduced. The kVp
Meter, divider, cassette results, and x-ray settings
should also be examined for constancy.
Multiple X-Ray Machine Method
If a voltage divider is not available, the following method may be used:
1. Choose several (if possible, at least five) x-ray machines suited for the test.
2. Make comparative measurements with each machine.
NOTE
NOTE
Data with a kVp test cassette may be useful. Be
sure to note positioning error and film usage when
using the cassette.
3. Record all parameters of the measurement, including geometry, cable connections, tube ID,
generator ID, and kVp Meter waveform oscilloscope pictures, oscilloscope, and voltmeter ID.