NARDA 8718B, User Manual

Page: 24 / 137

23 Chapter 4 Making a Measurement
Bar Graph Ranges
The Range key is used to control how the bar graph displays
information. The digital display is not affected and the meter
automatically displays a digital value over the probe’s entire
measurement range. There are four available settings: AUTO,
HIGH, MID, and LOW . The bar graph has 100 divisions.
You will probably find it convenient to use the AUTO setting
most of the time, but under a few conditions you may find one of
the three fixed ranges useful. The following table illustrates how
the range setting will affect the bar graph. For simplicity, a
probe with a full scale rating of 100 mW/cm
2
is used as an
example.
Range Measurement Range
AUTO As the field level increases the bar graph
automatically switches between three ranges:
0.01 to 1, 1 to 10, and 10 to 100.
HIGH 1 to 100
MID 0.1 to 10
LOW 0.01 to 1
If you exceed the upper limit of either the MID or LOW range, the
bar graph will be replaced with the message RANGE
OVERLOAD . The digital display will continue to show the
correct value. If you exceed the full scale measurement range of
the probe, the word "OVERLOAD" will appear
Testing the Probe
Your Model 8718B is equipped with two RF sources for testing
probes. Press Test Source and both sources will stay on for
approximately 20 seconds.
A contact on the right side of the unit is used for testing low
frequency probes and the low frequency section of
ultra-broadband probes. Most probes have three test points
around the head of the probe. Position the probe so that one of
the test points touches the contact on the meter. You should
The Range Key only
affects how the bar
graph displays infor-
mation.
N
ote