DayTronic 3000 series, Instruction Manual

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Daytronic Corporation
The signal is next applied to a phase-sensitive demodulator (active full-wave
rectifier). The amplified ac signal is synchronously demodulated to restore the
information content of the signal; that is, the amplitude and direction of the applied
force. The NULL pushbutton and associated circuit provide nonsynchronous
demodulation for balancing of the transducer bridge under
no load
conditions.
The dc output of the demodulator is buffered by an output amplifier which
contains the
Fine
SPAN adjustment and a
Symmetry
circuit. The
Symmetry
circuit
and its associated adjustment provide for compensating transducers with non-
symmetrical positive and negative characteristics.
The amplified analog signal is applied to two active low-pass filters, each of
which provide an output at the instrument I/O connector. The two outputs provide
passbands of dc to 2 Hz and dc to 400 Hz. Output selection is a trade off between
eliminating unwanted signals caused by vibration, etc., or increasing the time-to-
answer (slew rate) of the conditioner. The rolloff of each output is 60 dB within a
decade of the cutoff frequency.
5. VERIFICATION OF NORMAL OPERATION
It is the purpose of this section to aid the user in determining, in the event of a
malfunction to which the Model 3178 is suspected of contributing, whether the
instrument is functioning normally or whether it is the source of the observed
trouble. In the event the unit requires repair, a complete parts list, schematic
diagram, and component location drawing are included in this manual. The user
may also contact the factory Service Department or the local Daytronic Represent-
ative for assistance.
If the instrument is suspected of faulty operation, observe the following steps.
(a) If the unit is totally inoperational (front-panel power indicator does not
light), check the primary power fuse (Fl) located on the standup board
which forms the power cord connection point. If the fuse is blown,
replace it with a 0.50 ampere fuse (see Table 2 for part number). Before
reapplying power, visually inspect the power cord and the input power
connections for any discrepancy which could have caused the overload.
(b) If the transducer has some preloading, the BALANCE controls may not
allow successful zeroing of the instrument output. This condition can be
remedied by connecting a resistor (50 K-200 K range, metal-film type)
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