Test V-8: Internal Shunt - VXI VT1422A User Manual

8-pin Telcom
Connector (RJ-45)
Pin 1
Pin 8
10K
Pin 6
Pin 3
7.5K
Dummy Load
Pin 7
Pin 2
Pin 5
Pin 4
Test V-8: Internal
Shunt
Description
Appendix C
+Excitation
10K
+Excitation Sense
10K
+Sense
-Sense
Wagner
Voltage enable
10K
off for full bridge
-Excitation Sense
10K
-Excitation
350
120
customer
Local Rcal
Enable
-R Cal
+R Cal
Remote Rcal
Enable
Figure C-5. Signal Path for Shunt Cal Resistor Port Test
This test verifies the operation of the internal 50 kΩ shunt resistor and the
associated switches in the VT1529A/B.
Switch operation can be verified by observing the changes in the bridge
output voltage when internal shunt calibration is disabled and enabled.
The bending half-bridge strain path is configured and the Dummy Load is
attached. With the internal shunt disabled, the bridge output voltage should be:
V = V
sense excitation
With V
excitation
With the internal shunt enabled, the bridge output voltage should be:
V = V
sense excitation
Where R equals the parallel combination of the 7.5 kΩ resistor in the
Dummy Load and the 50 kΩ internal shunt or 6.522 kΩ. Again, with
V = 2.0 V, the expected value of V
excitation
Excitation
to CHs 1-7
Current
Limit
Instrument.
Amplifier
+
X16
-
Cal+ Cal-
+Excitation Sense
-Excitation Sense
50K
Internal
Rcal
Int/Ext Rcal
Select
Excitation Sense
from CHs 1-31
* (10 / (10 + 7.5) - 0.5)
= 2.0 V, the expected value of V
* (10 / (10 + R) - 0.5)
VT1529A/B Verification & Calibration
+ Excitation
- Excitation
enable excitation
Dynamic Strain
CHs 0-7
Output
Buffer
X2
CH00
CH01
To VT1422A
Optional
(VT1539A SCP)
Filter
Buffer
2,10,100Hz
32:1
X2
Mux
CH00
CH01
CH31
32:1
Mux
CH31
-R Cal
+R Cal
External customer
shunt cal resistor
terminals
Bridge Sense
from CHs 1-31
is 0.142857 V.
sense
is 0.210526 V.
sense
RJ-45
2:1
Mux
Cal+
Cal-
1k
475