Wiring and Noise Reduction Methods 485
Appendix E
VT1422A Guard
Connections
The VT1422A guard connection provides a 10 k
Ω
current limiting resistor
between the guard terminals (G) and VT1422A chassis ground for each 8
channel SCP bank. This is a safety device for the case where the Device
Under Test (DUT) isn't actually floating; the shield is connected to the DUT
and also connected to the VT1422A guard terminal (G). The 10 k
Ω
resistor
limits the ground loop current, which has been known to burn out shields.
This also provides 20 k
Ω
isolation between shields between SCP banks
which helps isolate the noise source.
Common Mode
Voltage Limits
Be very careful not to exceed the maximum common mode voltage
referenced to the card chassis ground of
±
16 volts (
±
60 volts with the
VT1513A Attenuator SCP). There is an exception to this when high
frequency (1 kHz - 20 kHz) common mode noise is present (see “VT1422A
Noise Rejection” below). Also, if the DUT is not grounded, then the shield
should be connected to the VT1422A chassis ground.
When to Make
Shield Connections
It is not always possible to state positively the best shield connection for
all cases. Shield performance depends on the noise coupling mechanism
which is very difficult to determine. The above recommendations are
usually the best wiring method, but if feasible, experiment with shield
connections to determine which provides the best performance for the
particular installation and environment.
NOTE
For a thorough, rigorous discussion of measurement noise, shielding and
filtering, see “Noise Reduction Techniques in Electronic Systems”
by Henry W. Ott of Bell Laboratories, published by Wiley & Sons,
ISBN 0-471-85068-3.
Noise Due to Inadequate Card Grounding
If either or both of the VT1422A and Agilent/HP E1482 (MXI Extender
Modules) are not securely screwed into the VXIbus Mainframe, noise can
be generated. Make sure that both screws (top and bottom) are screwed in
tight. If not, it is possible that CVT data could be more noisy than FIFO data
because the CVT is located in A24 space, the FIFO in A16 space; more lines
moving could cause noisier readings.
Содержание VT1422A
Страница 2: ...This page is blank...
Страница 8: ...8 Notes...
Страница 22: ...22 Support...
Страница 57: ...Field Wiring 57 Chapter 2...
Страница 58: ...58 Field Wiring Chapter 2...
Страница 96: ...94 Programming the VT1422A VT1529A B for Remote Strain Measurement Chapter 3...
Страница 162: ...160 Programming the VT1422A for Data Acquisition and Control Chapter 4...
Страница 224: ...222 Creating and Running Algorithms Chapter 6...
Страница 419: ...VT1422A Command Reference 417 Chapter 7 Notes...
Страница 420: ...418 VT1422A Command Reference Chapter 7 Notes...
Страница 425: ...Specifications 423 Appendix A Thermocouple Type E 200 800 C SCPs VT1501 02 03A...
Страница 426: ...424 Specifications Appendix A Thermocouple Type E 200 800 C SCPs VT1508 09A...
Страница 427: ...Specifications 425 Appendix A Thermocouple Type E 0 800 C SCPs VT1501A 02A 03A...
Страница 428: ...426 Specifications Appendix A Thermocouple Type E 0 800 C SCPs VT1508A 09A...
Страница 429: ...Specifications 427 Appendix A Thermocouple Type E Extended SCPs VT1501A 02A 03A...
Страница 430: ...428 Specifications Appendix A Thermocouple Type E Extended SCPs VT1508A 09A...
Страница 431: ...Specifications 429 Appendix A Thermocouple Type J SCPs VT1501A 02A 03A...
Страница 432: ...430 Specifications Appendix A Thermocouple Type J SCPs VT1508A 09A...
Страница 433: ...Specifications 431 Appendix A Thermocouple Type K SCPs VT1501A 02A 03A...
Страница 434: ...432 Specifications Appendix A Thermocouple Type R SCPs VT1501A 02A 03A...
Страница 435: ...Specifications 433 Appendix A Thermocouple Type R SCPs VT1508A 09A...
Страница 436: ...434 Specifications Appendix A Thermocouple Type S SCPs VT1501A 02A 03A...
Страница 437: ...Specifications 435 Appendix A Thermocouple Type S SCPs VT1508A 09A...
Страница 438: ...436 Specifications Appendix A Thermocouple Type T SCPs VT1501A 02A 03A...
Страница 439: ...Specifications 437 Appendix A Thermocouple Type T SCPs VT1508A 09A...
Страница 440: ...438 Specifications Appendix A 5k Thermistor Reference SCPs VT1501A 02A 03A...
Страница 441: ...Specifications 439 Appendix A 5k Thermistor Reference SCPs VT1508A 09A...
Страница 442: ...440 Specifications Appendix A RTD Reference SCPs VT1501A 02A 03A...
Страница 443: ...Specifications 441 Appendix A RTD SCPs VT1501A 02A 03A...
Страница 444: ...442 Specifications Appendix A RTD SCPs VT1508A 09A...
Страница 445: ...Specifications 443 Appendix A 2250 Thermistor SCPs VT1501A 02A 03A...
Страница 446: ...444 Specifications Appendix A 2250 Thermistor SCPs VT1508A 09A...
Страница 447: ...Specifications 445 Appendix A 5k Thermistor SCPs VT1501A 02A 03A...
Страница 448: ...446 Specifications Appendix A 5k Thermistor SCPs VT1508A 09A...
Страница 449: ...Specifications 447 Appendix A 10k Thermistor SCPs VT1501A 02A 03A...
Страница 450: ...448 Specifications Appendix A 10k Thermistor SCPs VT1508A 09A...
Страница 454: ...452 Specifications Appendix A...
Страница 480: ...478 VT1529A B Verification Calibration Appendix C...
Страница 484: ...482 Glossary Appendix D Notes...