g. Using a reference resistor of 90-110 MΩ, calculate the IR U-
constant
2
h. Using a reference resistor of 190-210 MΩ, calculate the IR
R-constant such that the QA-90 measures as closely as poss-
ible to that reference.
such that the QA-90 measures as closely as possi-
ble to that reference.
i. If you are unable to justify levels above 210 MΩ, it may be
necessary to change the measurement amplifier.
j. Check the range of 1-200 MΩ (e.g. 1, 10, 100 and 200 MΩ)
with Metron's test instrument. Press STOP (F1).
k. Press GO BACK (F2) to return to Main Setup Window 2
and press Mains on Applied Parts (F6).
l. Select (F7) to display Applied Part to Case.
m. Define the Patient Leads 1-10.
n. Measure the voltage between EARTH and applied part.
Adjust the voltage to 253 V
AC
for European Models or
132 V
AC
for US Models (Patient Leads 1-10).
o. Check that the current displayed on the UUT is in accor-
dance with Ohm’s Law (253 or 132 V
AC
/test-box imped-
ance). The measured alternating voltage, divided by the
voltmeter’s internal resistance.
p. Press GO BACK (F2) to return to the previous display.
5.4 Other Calibration Pro-
cedures
1. Bar Code Reader (Optional). This checks the QA-90 Bar Code
Reader function and its ability to properly accept scan and con-
2
On older QA-90 firmware versions there is only one constant IR U-constant
for insulation resistance measurements. On version series 0.xx there are six
constants, while on version series 1.xx there are seven. Also with the 1.xx
series, the IR U- and IR R-constants are used for insulation resistance mea-
surements.
NOTE
Remember that the patient
leads must be defined (1-10).
IMPORTANT
YOU HAVE TO PERFORM SEVERAL CALCULATIONS OF
THESE CONSTANTS BECAUSE OF THEIR INFLUENCE ON
EACH OTHER. IF THEY ARE CLOSE TO DEFAULT, FEW CAL-
CULATIONS ARE NECESSARY. HOWEVER, IF THE IR-R
CONSTANT HAS TO BE HIGH, MEASUREMENTS MUST BE
REPEATED TO OBTAIN THE BEST POSSIBLE LINEARITY.
NOTE
Never set any of the con-
stants higher than 99.999.
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