Crystal Instruments

Spider Q&A

  1. Do I need a PC to run the Spider-80?
  2. Many other dynamic measurement instruments are also modular. Why is Spider different?
  3. What are the advantages of a distributed over centralized system?
  4. Why is the accuracy of time synchronization so important to a DSA system?
  5. Where is the data stored on the Spider system?
  6. My sensor only has 60dB dynamic range. What is the benefit of the Spider's 130dB dynamic range?
  7. Does Spider-80 have an internal battery?
  8. Does Spider-80 have a permanent clock?
  9. How do I calibrate the System?
  10. How do I update the software on the Spider-80?
  11. What is the cost for service/repair if my Spider-80 system is out of warranty?
  12. Who is John Eidson?
  1. Do I need a PC to run the Spider-80?

    Yes and No. Spider has two working modes, PC mode and black box mode. In  PC mode, a Spider or multiple Spider modules are controlled by one PC. This is the same as many other PC based instruments. The user  runs the CI EDM software and conducts real time control with the Spider system. In black box mode, the tests are first configured through the PC, then the PC is disconnected and the settings stay at the flash memory of the Spider system. The tests can then run without the PC. A pre-programmed testing schedule can be executed so the data can be periodically saved into the Spider's local flash memory.

  2. Many other dynamic measurement instruments are also modular. Why is Spider different?

    Spider is probably the first DSA system that is modular at the user-level. Most other instruments are only modular at the manufacture level. For example, a VXI or PXI system consists of multiple plug-in cards that the manufacturer can configure. However it is not safe for the user to re-configure the systems with different modules. It is also impossible to divide the complete system into a few different systems and run them separately. Conversely, Spider modules are completely configurable by the user. If a company purchases two Spider-80 modules, they can use them as two separate 8-channel systems or combine them as one 16-channel system.

    Another benefit of the modularity is that users on a limited budget can start with a single 8 channel system, and then as the need and budget increase, they can simply purchase additional Spider modules to increase to a larger channel count system.

  3. What are the advantages of a distributed over centralized system?

    The first main advantage is that a distributed system eliminates much of the analog cables and reduces the influence of noise.  Distributed systems allow the measurement instruments to communicate to each other and the PC using digital instead of analog signals. On the contrary, a centralized system using a PXI, VXI or VME bus requires that all the measurement front end hardware be located close to each other, or in one chassis. A centralized configuration requires many long analog cables in order to connect the instrument to the sensors. A distributed system allows the user to place the measurement front end units close to the sensors. With such configuration the EMI interference to the analog cables can be significantly reduced and the cabling work can be simplified.

    This difference between distributed and centralized systems is illustrated in the two figures below.


    Figure 1 Centralized instrument requires multiple long sensor cables that may introduce electrical noise


    Figure 2 Spider positions the A/D converters closer to the signal source then transfers the data digitally

    The second advantage is the user can access the testing hardware system anywhere on the LAN. The user can view the live data from a control room, office or anywhere with LAN connection.

  4. Why is the accuracy of time synchronization so important to a DSA system?

    Time synchronization of the sampling clock for each A/D converter directly impacts the phase match between channels.

     

    All dynamic signal analysis systems define phase match specification between each input channels.  Modern instruments usually claim phase match between any pair of channels at better than ±1 degree up to 20kHz. Phase miss-match can be caused by several factors, including:

    (1). A slight variation of the synchronous clock signals going to each A/D converters

    (2). A slight variation of the group delay of the anti-aliasing filter of each channel.

    While distributed systems have many other advantages, the challenge is to make the sampling clocks on different boards function with precise synchronization. With IEEE 1588 technology, the Spider can achieve better than ±100 ns time synchronization accuracy between different boards. This ensures that the phase match of a large channel count system is better than ±1 degree up to 20kHz.

  5. Where is the data stored on the Spider system?

    There are two types of data files: recorded long waveform time stream data files and saved block signals. The long waveform time stream data is always recorded to the Spider on-board flash memory. This strategy ensures that the network speed will never affect the recording speed. After recording, the user can download the long waveform time stream data files to the PC or anywhere on the network. Block signals can be saved to either the PC or Spider modules locally.

  6. My sensor only has 60dB dynamic range. What is the benefit of the Spider's 130dB dynamic range?

    The real advantage of having a 130 dB dynamic-range is that the instrument can function without any input range settings. In traditional instruments, the input range settings, i.e., the amplifier gain, are where the operator can make the biggest mistakes. If you set the range too large, then you won't be able to measure small signals; if the range is too small, then the measurement may get overloaded. A handheld system will have more problems in such a setup. With the unique hardware design, the Spider-80 reaches a 130 dB dynamic range. The instrument can measure signals as high as +/-20V or as small as a few micro-volts without concern of input range settings. Given this advantage, users don't need the range setting in the channel table.

  7. Does Spider-80 have an internal battery?

    Yes. But this battery is used for backup purpose and is not designed for long time operation. When the external power is unexpectedly lost during the operation, the Spider will use the internal backup battery to support the operation until the data and test configuration is appropriately stored. The software will then shut down in an orderly fashion.

    This backup battery also provides a mean of stable power source.

  8. Does Spider-80 have a permanent clock?

    Yes. The permanent clock claims 10 years of life. The User can set the time and date through the EDM software.

  9. How do I calibrate the System?

    System calibration software is included with each system purchase. You can calibrate the system by yourself if you have a high quality AC/DC volt meter that is used as a calibration reference. However, we recommend that the calibration be done by CI or a designated service company.
    To calibrate the Spider-80 by yourself, you must have a voltmeter with valid calibration certificate. The voltmeter must be able to measure DC and True RMS to an accuracy of 0.25%. The AC bandwidth for the voltmeter should be higher than 5 kHz.

  10. How do I update the software on the Spider-80?

    Updating the Spider-80 can be done by using the EDM PC software. The EDM software detects the installed version on the Spider and then lets the user install the new software. The new software can be downloaded from the Internet with a valid user account.

  11. What is the cost for service/repair if my Spider-80 system is out of warranty?

    The minimum cost for service/repair of any system that is out of warranty is $300 (US). If however, the cost of the repair is found to exceed this minimum amount, you will be notified immediately.

  12. Who is John Eidson?

    John Eidson, a scientist worked for Agilent Lab for many years, is the main inventor of a high-precision time synchronization protocol that enables the use of Ethernet for real-time applications in test and measurement, telecommunications and industrial automation. His work resulted in an international standard, known as IEEE 1588,  that provides for precision timing in networks.

    Crystal Instruments highly regards John Eidson’s contribution to the industry and thanks his encouragement when Spider products were developed.

Crystal Instruments
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