DayTronic 3000 series, Instruction Manual

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Model 3178
cable provides connection from the 3178 calibration circuit to the calibration
resistor which is integral to the
1600 Series
transducers, without requiring the
removal of the 3178 calibration resistor.
When user-fabricated transducer cabling is used, it should take the form of
either the 4-, 5-, or 7-wire cable configuration shown in Figure 4. The 4-wire
configuration should be used when overall
deadweight
calibration is the method
used and the required cable length is less than 20 feet. The 5-wire configuration
should be used when the instrument is to be calibrated by achieving a precisely
known
Equivalent Input
value through the use of a shunt calibration resistor
supplied by the transducer manufacturer and when the required cable length is less
than 20 feet. The 7-wire configuration should be used with cable lengths longer than
20 feet since the excitation voltage is sensed and regulated at the transducer and
optimum shunt calibration can be achieved.
Remote Calibration Check.
The instrument can be placed in the calibration
mode (positive realm only) by shorting pins 5 (Signal Common) and 8 (Remote Cal)
of the rear-panel I/O connector. Figure 4 indicates three methods of remotely
entering the calibration mode (external switch, transistor, or TTL source). The
Remote Cal
function provides a convenient method of periodically monitoring
calibration of the instrument in the positive realm.
Master/Slave Connections.
When more than one 3178 (or a combination of
3178 or 3130 LVDT Conditioners) is being used in a measurement setup (instru-
ments are continuously mounted or the transducer cabling is in a common conduit
or raceway), beat frequencies may be produced from the 3-kHz oscillators used in
the instruments to develop the excitation. To prevent beat frequencies from occur-
ring, one unit can be designated the
master,
and the remaining units can be driven
from the oscillator contained in the
master
unit. The remaining units are designated
as slave instruments. To perform
master/slave
wiring, refer to Figure 4.
Analog Outputs.
Two analog outputs are available at the instrument I/O
connector, with each output having a different passband: dc to 2 Hz and dc to 400
Hz. The cutoff frequencies are achieved with active low-pass filters. When the
dc-to-2 Hz output is used, a trade off is made between noise elimination and
increased time-to-answer or slew time. Each output has a 60-dB rolloff a decade
from the cutoff frequency. The filter characteristics are given by the following
equations.
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