Note

The Range Key only affects how the bar graph displays infor- mation.

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/cm2 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

Chapter 4 Making a Measurement

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