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Model DRC-91C/93C
9305
Thermocouple
Input
Card
Table
9305-2
to the Lake Shore
An
Offset Adjustment is provided
DRC-91C
and
DRC-93C
Temperature
adjacent to the Terminal Block.
Controllers
over
their respective
This adjustment will zero out small
temperature ranges.
voltage offsets that result from
sensor
lead
attachment
and
The
thermocouple
voltage
is
differences
from
the
internal
amplified by
100
by a circuit which
curve.
is attached to the Terminal Block
.
The thermocouple voltage is further
9 3 0 5 . 6 . 1
Display Operation
amplified
by
a
factor
of
2
(tunable) by the Control Amplifier
Digitized
thermocouple
and
on
the
9305
Thermocouple Input
secondary sensor voltages on the
card.
9305
card are sent to the main
board
of
the controller.
The
The amplified signal is sent to the
secondary
sensor
temperature is
main
board
analog control circuitry
computed from its voltage and a
and
can
be
accessed
from
the
thermocouple voltage corresponding
Buffered Output line of the
J3
to the secondary sensor temperature
M o n i t o r
Connector
on
the
is calculated.
If correction is
controllers
back
panel.
In
selected, the compensation value is
a d d i t i o n ,
t h e
a m p l i f i e d
added to the thermocouple voltage.
thermocouple voltage is applied to
Corrected voltage
in
millivolts is
a
15
bit
A/D
converter on the
then used as a display value or
Thermocouple Input Card so that
converted
to
Celcius
degrees,
digitized thermocouple voltage can
Fahrenheit degrees, or Kelvin for
be
sent
to
the
main
board
display.
microprocessor.
The Thermocouple
A/D
converter has
an
auto-zero
9 3 0 5 . 6 . 2
Control
Operation
function which means that the only
calibration required is for the
Control operation begins when the
relative gain.
operator enters a Setpoint voltage
If the Setpoint is
A
secondary
diode
temperature
in
temperature,
the main
board
sensor is attached to the Terminal
computes
an
equivalent
voltage
Block
to monitor
the reference
using
the
built-in
Thermocouple
junction
temperature needed
for
t a b 1 e
.
T h e
m a i n
board
Reference Junction Compensation. A
microprocessor then checks to see
constant current source on the
9305
if Reference Junction Compensation
Card
is applied to the Secondary
is enabled.
Sensor.
A
15
bit A/D converter
on the
9305
Card digitizes the
If
the
Reference
Junction
secondary sensor voltage and sends
Compensation is disabled, a signal
the
data
to
the
main
board
which is 200 times the digital
microprocessor. The microprocessor
value
of
Setpoint
voltage
is
on the main board of the controller
applied to the Setpoint
D/A
to
calculates the reference junction
obtain the Setpoint voltage for
temperature.
The
reference
control.
junction temperature is used
in
compensation to account for the
If
t h e
Reference
Junction
difference between room temperature
Compensation is enabled, a voltage
and the normalization temperature
corresponding to the Terminal Block
of
the
curves,
zero
degrees
temperature is subtracted from the
Celcius.
Setpoint voltage.
A
signal which
is
200
times the digital value as
COPYRIGHT
6/88
LSCI
9305-5
in millivolts.
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