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NOTE: If the TR8703 is connected to a computer, Auto mode will
be disabled. The Measurement Record will not be saved in the
instrument but will be sent to the computer.
3.3.6. Select Filter
1. From the top level of Configure Instrument, press the ▼ or ▲ key until
Select Filter appears on the display, then press ENTER.
2. Select Fast, Normal or Slow using ▼ or ▲ and press ENTER. The
display will return to Configure Instrument > Select Filter.
NOTE: The TR8703 offers the user a choice of three digital filters
for measurement, depending upon the external electrical noise.
These are sophisticated digital filters in the design which offer
maximum noise rejection for repeatable measurements.
Digital filters:
The digitization of signal is done with Sigma-Delta (Σ-Δ) modulator. The
output is a high frequency bit stream which is fed to a digital filter. The
filtering of signal is performed with sophisticated sinc (Sinx/x) filter. The
primary function of the filter is to remove the quantization noise introduced
during the modulation process.
The filter limits the band of the allowed frequency to significantly lower
than one-half of the frequency of the modulator itself. This reduces the 1-
bit output of a comparator in a band-limited, very low noise output. The
cut-off frequency and the decimated data rate are appropriately
programmed in the internal registered and the output is arithmetically
averaged to provide an accurate final answer.
High decimation results in lower noise but at a slower throughput rate.
The calculation of arithmetic mean is a quick process at high clock
speeds of the microprocessors.
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