Tektronix CMC251, User Manual

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CMC251 User Manual
9
Reference
This section describes typical setups of the CMC251 Frequency
Counter for each of its measurement modes.
Making Frequency Measurements
Measuring frquencies with the CMC251 Frequency Counter is
simple, although there are some items you need to consider before
applying the signal to the inputs of the frequency counter.
1. Estimate the frequency of the signal source and determine the
voltage level.
This enables you to use the appropriate input channel of the
frequency counter. A good practice is to display the signal on an
oscilloscope and obtain the peak voltage level. Refer to Table 1
and pick the appropriate input channel.
Table 1: A or B Channel Input
Estimated Frequency Input Voltage Proper Input Channel
1 Hz to 100 MHz Less than 42 V peak CHANNEL A INPUT
80 MHz to 1.3 GHz Less than 1 V
RMS
CHANNEL B INPUT
2. Prepare to make a measurement, using the steps under one these
sections: Frequencies Below 10 MHz, Frequencies Below
100 MHz, or Frequencies Between 80 MHz and 1.3 GHz.
Frequencies Below 10 MHz
1. Press the FUNC button until FREQ A is indicated with a lighted
LED.
2. Refer to Table 2 and set the frequency counter front-panel buttons
to obtain the best measurement for frequencies below 10 MHz.