Philips PM2519 - Page 27

2.3.2.8. Frequency measurements
The Hz function switch, connects the input signal to be measured via the attenuator to the RMS converter.
The attenuator factor of the attenuator is 10 in all frequency ranges. The range of the RMS-converter is always
900 mV. Input SEL (RNG H) is switched to logic 0. This means that the zero-crossing detection is enabled.
The output CF will give a square wave with a frequency which is equal to the input frequency. The square
wave is fed to a divider which divides the frequency by either 10 or 100. This depends on the frequency range
which is selected. At the beginning of a frequency measurement, first select the highest range to see if the right
range has been selected. This is done by means of enabling the 100 times divider.
DIVIDING MEASURING TIME
To create a 1000 Hz range the measure time is 10 s instead of 1 s.
FREQUENCY
1000 Hz
10 kHz
100 kHz
1MHz
RMS CONVERTER
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Fig. 2.8. Frequency measurements