Sperry instruments DSA-2417, Руководство по эксплуатации

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Frequency response of 40 Hz to 1 kHz permits measurements of current with
harmonics superimposed on the fundamental frequency. High frequency current from
appliances such as inverters, switching regulators etc. can therefore be measured.
NOTE
• DSA- 2417 has a very good frequency response due to the electrical
property of the transformer jaws used for the instruments. Therefore, it
measures AC current of not only
50 Hz or 60 Hz fundamental wave form but
also of higher frequencies and harmonics superimposed on the fundamental
frequency when present in the circuit under test. To eliminate the effect of
noise from the high frequency and measure AC current of
50 Hz or 60 Hz
fundamental frequency, a filter circuit is incorporated into DSA- 2417 which
works when the frequency selector switch is set to the 50 / 60 Hz position.
It is designed to attenuate frequencies starting from around 100 Hz with an
attenuation characteristic of approx. - 24 dB/octave (signal strength declines
to one sixteenth of that at the initial frequency when it doubled). Recently
there has been increased usage of power through inverters, switching
regulators, etc. When the high frequency noise from such appliances leaks
or flows into the ground through capacitors not filtering completely, the
earth leakage breaker may not trip. In such a case the instruments may
not give current readings with the frequency selector switch at the
50 / 60
Hz position. Therefore, it is necessary to make current measurements
with the switch at the WIDE position. When in doubt as to the presence
of high frequencies and harmonics that affect AC current measurements,
take current readings with the switch at the
50 / 60 Hz and WIDE positions
respectively and then compare the results obtained.