METRON QA-ES, User & Service Manual, Page: 27 / 55

Meas s
R
R
Re
*
=
+
1 100
1 100
4. Measuring Device
Measuring The Effect . Set the QA-ES in test mode by holding
F2 while switching the power on. Connect the signal generator
to the RF input on the sampling unit. The signal applied is a
pure sine of 500 kHz. URE 3 is connected in parallel with the
sampling unit to measure the applied signal. Press START (F3)
and read the measured effect in dB. Vary the level of the ap-
plied signal from -16 dBm to +10 dBm and find the average
value for the difference between the value read on the QA-ES
and the applied value measured with URE 3. Use the term be-
low to calculate a linear percentage value from the difference
value in dB.
KdB: Average value for the difference between the value read
on QA-ES and the applied value measured with URE 3.
Clin
kdB
=
20
10
Clin: Linear value of kdB.
gain gain
Q Q
Clin
= •
The following term will lead to a new value for Q_gain .
Turn the wheel and press ENTER to specify a new value for
Q_gain . Repeat the test until the average value between the
QA-ES and URE 3 is smaller than 0.1 dB. This corresponds to
an error of 2.3%.
Peak Detector . Once the measuring device used in measuring
the effect has been calibrated, you can calibrate the peak detec-
tor. Use the same test setup as for calibrating the effect. Mea-
sure with a signal level of 200 mVp and 1 VP applied from the
generator. The applied amplitude is measured with URE 3. The
difference between the value read on the QA-ES and URE 3
should not exceed 10% otherwise the
P_offset and N_offset in
the calibration menu must be changed until this requirement is
met. If the positive peak value read is too small
P_offset should
be reduced. N_offset should be reduced if the negative peak
value is too low. Press QUIT (F5) to save calibrated values.
5. Measuring Accuracy of the total system . Connect the coaxial
cable from the Load Board to the RF-input (J4) on the Sampling
Unit. Put the ground plate of the isolating box back into place.
Connect a high voltage probe in the port for variable load resis-
tance on the QA-ES. The probe's coaxial cable should be con-
nected to URE 3. The banana adapters of the probe are connect-
ed with the high voltage generator. The following mathematical
formula presents the applied effect in dBm as a curve of the ef-
fect on URE 3.
3