3.e C
ONTROL OF
10A74-4C T
RACK
/H
OLD
O
PERATION
VIA
L
OGIC
I
NPUT
When the 10A74-4C's rear I/O CONNECTOR is not dedicated to a Model 10QBC-
4, 10HBC-4, 10FBC-4, or 10VAC, its
Pin K
can be used as an alternative source of
TRACK/HOLD control (see Fig. 6). As with Pins 9 and 10, logic levels for Pin K are
negative true, resulting in a Logic 1 level at the pin when it is unconnected. A
Logic 1 (0 V) level at the pin keeps all four 10A74-4C analog input channels in
"TRACK" mode, while a Logic 0 level (+5 V) keeps all four channels in the "HOLD"
mode.
4
L
EAD
-W
IRE AND
N
ONLINEARITY
E
FFECTS WITH
Q
UARTER
-B
RIDGE
S
TRAIN
G
AGE
C
ONFIGURATION
In stress analysis applications, it often happens that the completion resistors for a
quarter-bridge strain gage are located some distance from the gage. If the resistance
of the wires connecting the gage to the completion circuitry is considerable, it can
"desensitize" the bridge, producing less output voltage from the bridge for a given
amount of strain as the wire resistance increases.
A second cause of possible inaccuracy is the slight nonlinearity inherent in all bridge
configurations. This nonlinearity is proportional to the amount of "upset" of the bridge.
For small amounts of strain (below about 5000 microstrain, with a gage factor of 2),
the output is nearly linear. However, as the change in gage resistance increases due
to increasing strain, the nonlinearity effect becomes measurable.
4.a P
REVENTING THE
E
FFECTS OF
L
EAD
-W
IRE
R
ESISTANCE
When connecting a Model 10A74-4C to a quarter-bridge strain gage configuration,
you can eliminate all effects of reasonable lead wire resistance by using a Model
10CJB-4 Four-Channel Bridge Completion Card
in the vicinity of the gages, since
the 10CJB-4 has inherent bridge-voltage sensing. WHERE THIS IS NOT POSSIBLE,
YOU SHOULD USE A SHUNT CALIBRATION PROCEDURE with a three-wire run to the
gage (see Fig. 8).*
10A74-4C.
14
L
EAD
-W
IRE AND
N
ONLINEARITY
E
FFECTS
10A74-4C
Q
UAD
DC S
TRAIN
G
AGE
T
RACK
-H
OLD
C
ARD
* Buffered by a low-offset, low-drift, high-impedance, unity-gain amplifier (A), the solid-state
shunt-calibration switch prevents the shunt current from flowing in the excitation sense lines.
The switch itself is controlled by the software
SHUNT CALIBRATE—POSITIVE (SHP)
,
SHUNT
CALIBRATE—NEGATIVE (SHN)
, and
RESUME (RSM)
commands.
Side 2
1 MV/V OFFSET
+
–
A
B
C
D
Fig. 7 Model 10CJB-4
Offset Jumpers
Summary of Contents for System 10
Page 31: ...GETTING YOUR SYSTEM 10 ON THE AIR SB 2 FOR A SIZED MAINFRAMES...
Page 67: ...GETTING YOUR SYSTEM 10 ON THE AIR SB 2 FOR B SIZED MAINFRAMES...
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Page 174: ...10A16 4C 6 THIS PAGE INTENTIONALLY BLANK 10A16 4C QUAD PLATINUM RTD CARD...
Page 186: ...10A18 4C 8 THIS PAGE INTENTIONALLY BLANK 10A18 4C QUAD PLATINUM LINEAR RTD CARD...
Page 212: ...10A40 8 THIS PAGE INTENTIONALLY BLANK 10A40 FREQUENCY CARD...
Page 224: ...10A43 4 THIS PAGE INTENTIONALLY BLANK 10A43 DWELL ANGLE CARD...
Page 234: ...10A48 6 THIS PAGE INTENTIONALLY BLANK 10A48 FLOW CARD...
Page 242: ...10A61 2 4 THIS PAGE INTENTIONALLY BLANK 10A61 2 DUAL 4 20 MA CARD...
Page 252: ...10A63 2 6 THIS PAGE INTENTIONALLY BLANK 10A63 2 DUAL DC VOLTAGE CARD...
Page 270: ...10A69 4 6 THIS PAGE INTENTIONALLY BLANK 10A69 4 QUAD AC RMS CARD...
Page 276: ...10A70 2 6 THIS PAGE INTENTIONALLY BLANK 10A70 2 DUAL DC STRAIN GAGE CARD...
Page 288: ...10A72 2C 12 THIS PAGE INTENTIONALLY BLANK 10A72 2C ENHANCED DUAL DC STRAIN GAGE CARD...
Page 320: ...10A74 4C 18 THIS PAGE INTENTIONALLY BLANK 10A74 4C QUAD DC STRAIN GAGE TRACK HOLD CARD...
Page 342: ...10A96 8 THIS PAGE INTENTIONALLY BLANK 10A96 AMPLIFIED ACCELEROMETER VIBRATION CARD...
Page 362: ...AA30 4 12 THIS PAGE INTENTIONALLY BLANK AA30 4 QUAD LVDT CARD...
Page 374: ...AA41 2 4 12 THIS PAGE INTENTIONALLY BLANK AA41 2 AA41 4 DUAL QUAD FREQUENCY CARD...
Page 390: ...AA72 2 4 16 THIS PAGE INTENTIONALLY BLANK AA72 2 AA72 4 DUAL QUAD DC STRAIN GAGE CARD...
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