DayTronic 3000 series, Instruction Manual

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Model 3178
designated as
slave
instruments. The
Oscillator In
terminal of each
slave
unit (at the
instrument I/O connector) provides a connection point to the
Oscillator Out
termi-
nal of the
master
unit. The
Oscillator Out
and
Oscillator Disable
terminals of the
slave
units are jumpered to disable the oscillator internal to these units.
Calibration Circuit.
A
Cal Sense
line is returned from the +
Signal
connection
at the transducer to provide for shunting the
Cal Resistor
across a bridge leg to
simulate an
Equivalent Input.
When the +CAL button is pressed, the
Cal Resistor
is shunted across the +
Signal
and +
Sense
connections. This action occurs by
grounding the negative input of a
Comparator
through the +CAL switch. The
Comparator
output then closes an analog switch to which the
Cal Resistor
is
connected. The connection to the +
Sense
line is then made through normally-
closed contacts of the –CAL switch. Similarly, when the –CAL button is pressed,
the
Cal Resistor
is shunted across the +
Signal
and –
Sense
connections. The
Comparator
is exercised as when the +CAL button is pressed, and the
Cal Resistor
is switched to the –
Sense
line through the normally-open contacts of the –CAL
switch.
Calibration in the positive realm can also be remotely checked. When the
Remote Cal
input at the 3178 I/O connector is brought to a zero-volt (ground) level
through the action of an external switch, transistor driver, etc., the same action
occurs as when the +CAL button is pressed.
A line from the
Cal Resistor
is also provided for use with Lebow
1600 Series
rotary transformer torque transducers. This type of transducer has an integral
Cal
Resistor
installed by the manufacturer. The line provided from the Daytronic
Cal
Resistor
enables the use of the Lebow
Cal Resistor
without removing the resistor
integral to the 3178.
Signal Conditioner.
The +
Signal
and –
Signal
inputs from the transducer are
applied to a differential ac signal amplifier with excellent common-mode rejection.
Summed into the amplifier are the appropriate resistive and capacitive nulling
voltages from the R and C BALANCE controls. These enable the operator to set the
3178 output to zero under transducer
no load
conditions.
A high-pass filter/amplifier follows the input differential amplifier to provide
the required gain and eliminate 60-Hz ripple or noise related to the rotational
frequency of the device when a rotating transformer torque transducer is used. The
Coarse
SPAN control is situated at the output of the amplifier to provide a gain
control.
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