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Model DRC-91C/93C
9317C/9318C Input
Cards
point voltage which will result in
set point
results in an under-
a sensor voltage as close to 1.05
temperature condition, the opposite
or
10.5
millivolts
as possible
operation is performed.
(when the control point is reached)
is calculated.
If the thermal
If
the
thermal
correction
is
correction is active and there has
active, the 91C/93C monitors the
been a valid thermal value deter-
sensor
resistance
until
it
is
mined,
it
is
included
in
the
within
0.5%
of
the
set
point
calculation.
If no valid thermal
resistance.
Once
it
is,
the
has been determined, or the thermal
91C/93C
signals
the
9317C/9318c
correction is inactive, a thermal
card
to reverse the sensor current
value of
0
is used.
The resultant
and update the thermal value.
The
voltage is then sent to the main
9317C/9318C card and the 91C/93C
board of the controller as the set
use this new thermal to determine
point
voltage
(or
equivalent
the resistance and correct the set
"resistance") for control.
point.
The
thermal
value
is
updated every
120
instrument update
The 9317C/9318C input card then
cycles (about
2
minutes) after the
determines if the control sensor
initial update.
When the set point
resistance is above or below the
is changed, the previous thermal
equivalent set point "resistance".
value is used until the correction
If the actual resistance is less
criteria is met and the thermal
than the set point "resistance", an
updated again.
over-temperature condition exists
and the heater power should be off.
9317C/9318C.6
CALIBRATION
SCHEDULE
The 9317C/9318C changes the current
AND EQUIPMENT
it applies to the sensor in order
to maintain between 0.8
and 1.0
The
design
of
the
9317C/9318C
(9317C) or
8
and
10
(9318C) Resistance Input Card is such that
millivolts across it until the set
re-calibration
should
not
be
point current range and value have
required more often than every six
been reached.
In this way, the
to twelve months in order to keep
heater remains off until the actual
the
card
within
its
accuracy
sensor resistance approaches the
specification.
However,
if re-
set point "resistance". Once the
calibration
is
required,
the
final control sensor current value
following equipment is needed to
has been reached, the 9317C/9318C
re-calibrate the card:
allows the sensor voltage to range
as
high
as
1 . 3
(9317C) or
13
1 .
Digital Voltmeter (DVM)
-
5 1/2
(9318C) millivolts.
If the sensor
digit resolution or better.
voltage
(and
the
equivalent
resistance) continues to increase
2 .
Five
(5)
Precision
Standard
(an under-temperature
condition
Resistors which are accurate in
exists),
the
9317C/9318C
then
value to at least 0.01%.
Their
reduces the current to maintain
values
in
ohms must be:
between
1.1
and
1.3
(9317C) or
11
and 13 (9318C) millivolts across
9317C: 1,
10, 100, 1K,
1 0 K
the
sensor.
The
heater
power
9318C:
10, 100, 1K, 1 0 K ,
100K
remains on.
Even
though this
operation takes the sensor voltage
3.
Precision
Voltage
Standard-
away from the optimum signal until
capable of a plus and minus
10
it reaches the control point, the
millivolt signal to within ±0.1
resulting error in the resistance
microvolt.
determination is small.
If the new
COPYRIGHT 12/87 ISCI
93 17C/93 18C-5
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