METRON QA-ES, User & Service Manual, Page: 28 / 55

dBcoeff
R R
R
= •
+




20
1 2
2
log
R1:
Resistance in the high voltage probe. Specified on the
probe. Nominal value 47 kohms.
m URE
P P
dBcoeff
− +
#
R2:
Measuring resistance in the high voltage probe. Speci-
fied on the probe. Nominal value 37.5 ohms.
The measuring accuracy of the QA-ES should be checked for
the following resistance values and the corresponding signals
applied.
R Applied signal measured on URE3
[ohms] [W] [dBm]
75
200
∀
50W
52.0 - 54.0
300
150
∀
50 W
50.0 - 53.0
1500
100
∀
50 W
47.0 - 52.0
Calculate the average value for the difference between QA-ES
and URE 3 and correct the value for Q_gain in the calibration
menu by following the instructions given before under item 4 in
this section.
Requirement:
m qa es
P P
dBm dBm dB
[
[ ] [ ] .
− <
−
017
qa es
I
mA
−
>
50[ ]
In linear form this corresponds to:
m qa es
m
P P
P
−
<
−
4%
6. Scope Output . Connect the high voltage generator to 'Var.
Load' and the oscilloscope to 'Scope Output'. Set the QA-ES to
continuous mode and start measuring by pressing on
Start . Ac-
tivate the high voltage generator and measure the peak-to-peak
voltage on the oscilloscope. Check that this value equals the
current flow read on the QA-ES.
Nominal value: 4.5
∀
0.4 V/A
NOTE
Remember to set the ref-
erence impedance in
URE 3 to the same value
as the load resistance
used for measuring.
Remember that the
scope output is not cali-
brated!
4