IEC 60580:2000 pdf free download – Medical electrical equipment
3.17 INTRINSIC ERROR
deviation of the MEASURED VALUE(i.e. the INDICATED VALUE,corrected to REFERENCECONDITIONs) from the cONVENTIONAL TRUE VALuE under STANDARD TEST CONDITIONS (IEC 60731)
3.18 IONIZATION CHAMBER
detector consisting of a chamber filled with a suitable medium, usually gaseous, in which anelectric field， insufficient to induce charge multiplication, is provided for the collection at theelectrodes of charges associated with ions and the electrons produced in the SENSITIVEvoLUME of the detector by ionizing radiation
NOTE For use with DOSE AREA PRODUCT METERS，IONIZATION CHAMBERS are constructed in such a way as to allowthe air inside the measuring volume to communicate freely with the atmosphere.Sealed chambers are not suitablefor use with DoSE AREA PRODUcT METERS, because the necessary wall thickness of a sealed chamber may cause anunacceptable energy dependence of the RESPONSE and because the long term stability of sealed chambers is notguaranteed.
3.19 IRRADIATION TIME
duration of irradiation determined according to specific methods, usually the time during whichthe rate of a RADIATION quantity exceeds a specified level
3.20 LEAKAGE CURRENT
any current in the signal path arising in the detector and/or MEASURING ASSEMBLY which is notproduced by ionization in the IONIZATION CHAMBER
4.5.2.2 Any tests may be carried out using the complete DosE AREA PRODUCT METER;inparticular this is the preferred method for investigating the effects of high-frequencyelectromagnetic fields and electrostatic discharges on a cable-connected I0ONIZATiON CHAMBERsupplied with a MEASURING ASSEMBLY as a system. Some tests performed with the wholesystem cannot give information as to whether the origin of the vARIATIoN lies in the lONIZATIONCHAMBER or in the MEASURING ASSEMBLY(e.g.LEAKAGE CURRENT and zERO DRIFT). If a completesystem is tested and the relevant INFLUENCE QUANTITY affects both parts， the quadratic sum ofthe separate LIMITs OF VARIATION may be taken as an overall LIMIT OF VARIATION.
4.5.3 STABILIZATION TIME
The instrument shall be switched on for at least the STABILIZATION TIME quoted by theMANUFACTURER,before the start of the compliance test.
In addition， the lONIZATION CHAMBER should be allowed to attain thermal equilibrium with theenvironment and it should have the polarizing voltage applied for a period of time equal to orgreater than the specified STABILIZATiON TIME.
4.5.4Adjustments during test
Compliance tests shall be performed with the instrument ready for use, after the sTABILIZATIONTIME and after making any necessary preliminary adjustments. During the tests,adjustmentsmay be repeated at intervals as long as they do not interfere with the effect to be verified. Forexample, zero setting is not permitted during tests for measuring the LEAKAGE CURRENT.
4.5.5Uniformity of radiation field
The uniformity over the part of the usEFUL FIELD used for the compliance test shall bechecked,for example，by scanning the radiation field with a small IONIZATION CHAMBERcompared with the size of the usEFUL FIELD.Appropriate corrections shall be made to ensurean uncertainty of the test results of not more than one-fifth of the LiMITs OF VARIATION undertest.
NOTE The field uniformity of any X-RAY TUBE is subject to deterioration in use; regular checks should therefore bemade.