ETS-Lindgren HI-1710 Microwave Measurement System (Archived) - Manual (Page 41)

Page — 36 HI n 1710 Manual
Filter 2 (F2) is also a two pole Butterworth filter, but with
a 2 Hz. cutoff. The response of this filter is much faster
and is equivalent to the "FAST" response of an analog
survey meter.
Filter 3 (F3) is an eight pole Butterworth filter with a
cutoff frequency of 0.45 Hz. This filter was computer
optimized for testing ovens having slow mode stirring
devices.
Filter 4 (F4) is an eight pole Butterworth with a 0.9 Hz.
cutoff frequency. This filter was designed for ovens using
faster mode stirring devices such as air or motor driven
fan type stirrers. These filter functions can be used in
specially designed test programs which can allow faster
scanning (probe motion) speeds.
After filtering, the final leakage value is displayed on the
four digit, seven segment display. The microprocessor
also performs the peak hold and alarm functions. In the
Peak Hold mode, the Bar Graph display is driven without
any digital filtering to display the real time variations in
the RF level. In the Peak Hold mode, the highest reading
sent to the digital display by the processor is held and
continuously displayed until either a higher reading is
transmitted or until the instrument is zeroed. The peak
value displayed is the value obtained after all filtering is
accomplished.
When the instrument is not in the peak hold mode, the
Bar Graph display responds to the filtered signal as
displayed.
On startup and each time the instrument is zeroed, the
system performs a series of self-tests. The bias voltage
is measured to check for defective diodes and for a
Archived 4/2/10