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Model
DRc-91C/93C
9317C/9318C
Input
Cards
4 .
Connect
the
wiring
harness
eres (Range
4).
Each range has
64
mating
connector
to
the
independent current values.
The
9317C/9318C
Input Card making
ranges
overlap
each
other
(for
sure that the wiring harness
example, Range 1
-
Value
60
is
locking tab
is
seated over the
equivalent to Range
2
-
Value 6) so
extended
edge
of
the wiring
that a smooth transition from range
harness mating connector.
Plug
to range can be made.
The current
the 9317C/9318C into the Input
value, as well as direction, is
C a r d
Slot with the component
controlled by a
16
bit bipolar D/A
side facing to the left of the
converter.
This current resolution
unit as viewed from the front.
is
required to maintain as close to
Make sure the card is thoroughly
1.05
(9317C) or
10.5
(9318C)
seated.
Verify that the wiring
millivolts across the sensor as
harness is
in
place correctly by
possible.
The on-card microproces-
noting that the "A" or
"B"
on
sor stores calibration constants
the
harness connector is facing
for each of the four ranges at the
up
(if
it is not, review the
end point values of
6
and
60
for
harness installation again).
both
the
positive
and
negative
directions (a total of
16
current
5 .
Install the calibration cover by
calibration constants in all).
reversing step
2.
The resulting sensor voltage is
6.
Install the top panel.
converted from a differential to
single ended signal and amplified
9317C/9318C.
5
OPERATION
by a factor of
1000
(9317C) or
100
(9318C).
The amplified signal is
The
9317C/9318C
is
a
highly
digitized
by
a
microprocessor
complex, microprocessor controlled
controlled
15
bit A/D converter.
Input
Card.
It's
resistance
The
microprocessor
also
has
measuring technique
is
distinctly
calibration constants stored
for
different from the way a DMM would
the gain and offset of the input
measure
resistance.
Most
DMMs
amplifier.
As a result of the A/D
force a large enough signal across
resolution and calibration constant
the device being measured to make
manipulation of the sensor signal,
any
thermal
offset
negligible.
the sensor signal can be digitized
using this method in a cryogenic
with a resolution of
1
part in
environment could add a significant
10,000
over most of the resistance
amount of power, in the form of
range
the
9217C/9318C
covers.
sensor self heating, to the test
There is also a sample-and-hold
system. The 9317C/9318C Input Card
network on the card so that when
limits the amount of power added to
the sensor signal is reversed for
the system by limiting the voltage
thermal correction while controll-
across the sensor to
1
(9317C) or
ing, the correct polarity of the
10
millivolts
(9318C).
The
control signal is maintained.
9317C/9318C can also reverse the
current
polarity
in
order
to
9317C/9318C.5.1
Thermal Correction
correct for thermal EMFs in the
Selection for the DRC-91C
sensor connections and leads.
The
control
thermal
correction
The 9317C/9318C current source has
function
is
enabled or disabled
four ranges:
0.1
to
1
microamperes
using switch
3
of the appropriate
(Range 1),
1
to
10
microamperes
SENSOR ID located
on
the rear panel
(Range 2),
10
to
100
microamperes
of the DRC-91C.
(Range 3) and
100
to
1000
microamp-
COPYRIGHT 12/87 LSCI
93
17C/93 18C-3
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