Fluke Biomedical 35080M - Manual (Page 13)

35080M
Operators Manual
2-2
2.5 Oscilloscope Zero and Offsets
It is assumed that the operator is familiar with the use of a
storage oscilloscope. The following examples are for
oscilloscopes with 8 major divisions for vertical scales and
sensitivity selections of 0.1 V/div and 0.2 V/div. The selection
of time scales or triggering are not discussed in this manual.
Figures 2-1A & 2-1B show suggested oscilloscope settings for the 50-150 kV range using the Wide
Range Filter Pack (37617).
1. Insert the Wide Range Filter Pack (37617) into the Model 35080M kVp Divider and connect the kVp
divider to the oscilloscope.
2. Set the oscilloscope gain to 0.1 V/div, DC Coupled. This setting corresponds to a 10 kV/div
sensitivity.
3. If making kV measurements from 50 to 120 kV, set the oscilloscope coupling from DC to GND and
adjust the vertical position control so that the oscilloscope trace coincides with the bottom horizontal
line on the screen, which corresponds to 40 kV. Then set the oscilloscope coupling back to DC and
the kVp Divider function switch to the ‘‘CAL’’ position. Verify that after a delay of several seconds
the trace on the oscilloscope coincides with middle horizontal line on the screen, which corresponds
to 80 kV. When switching to the ‘‘RUN’’ position, a slight offset may be noted on the oscilloscope.
Do NOT readjust the oscilloscope trace to compensate for this offset. Refer to Figure 2-1A.
4. If making kV measurements from 120 to 150 kV, set the function switch of the kVp divider to the
‘‘CAL’’ position and adjust the oscilloscope vertical position control so that the oscilloscope trace
coincides with the bottom line on the screen, which corresponds to 80 kV. Refer to Figure 2-1B.
If the accuracy of the Model 35080M kVp Divider is in
question, the output voltage may be checked with a ± 0.1%
DVM. The proper CAL voltage is on the filter pack label. The
allowed tolerance is ± 1%. A 1% error will cause at most a
0.75% error in the kV reading.
NOTE
NOTE