Test V-4: Bridge Resistors - VXI VT1422A User Manual

8-pin Telcom
Connector (RJ-45)
Pin 1
Pin 8
Pin 6
20K Pin 3
Dummy Load
Pin 7
Pin 2
Pin 5
Pin 4
Procedure
Troubleshooting Failures
Test V-4: Bridge
Resistors
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
Int/Ext Rcal
Enable
Figure C-2. Signal Path for Sense Out Test
Set the Voltage Source to +5.000 V. Send the MEAS:VOLT:EXCitation?
(@<ch_list>) command to the VT1422A. The expected measurement value
is approximately +2.5 V on each channel.
Check that the Dummy Load is wired and working correctly and firmly
seated in the RJ-45 input connector. If all 8 channels of one block of
VT1529A/B channels are failing, check that the Voltage Source is
connected to the correct terminals on the Bridge Excitation input on the
VT1529A/B.
This test verifies the operation of the internal bridge completion resistors
and associated switches in the VT1529A/B.
The operation of the internal bridge resistors can be measured by
unbalancing the bridge circuit. The bridge output voltage is a function of the
resistor value as given by the following formula:
V = V
sense excitation
Excitation
to CHs 1-7
Current
Limit
Instrument.
Amplifier
+
X16
-
2,10,100Hz
Cal+ Cal-
+Excitation Sense
-Excitation Sense
50K
Internal
Rcal
Select
Excitation Sense
from CHs 1-31
* (10.0 / (10.0 + 7.5 + 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
32:1
X2
Mux
Mux
CH00
CH01
CH31
32:1
Mux
CH31
-R Cal
+R Cal
External customer
shunt cal resistor
terminals
Bridge Sense
from CHs 1-31
RJ-45
2:1
Cal+
Cal-
467