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  1. davidd31415

    How to measure high dust concentrations?

    Does anyone know of a measurement device rated for dust concentrations from 2000 mg/m^3 to 4000 mg/m^3? The dust particles are 20 um to 30 um in diameter. The dust is being agitated one or two times an hour in an environmental test chamber. I am looking for the least expensive (low accuracy...
  2. davidd31415

    Using RFID tags instead of labels for calibration information?

    Does anyone know if ISO standards permit the use of RFID tags as opposed to labels for identifying calibration information on measurement devices?
  3. davidd31415

    How do you store and organize accelerometer cables?

    Not sure what happened to the end of my original post there, I was meant to write "the length of the cables may make it impractical." Thanks Steve, I like the accelerometer box idea. Out of curiosity, have you found the cable to effect the calibrations? David
  4. davidd31415

    How do you store and organize accelerometer cables?

    This may seem like an elementary question but does anyone have a recommendation on how to store and organize accelerometer cables? I have been winding each cable and placing it in a plastic Ziploc bag. Perhaps this simply is the best method? I’ve tried plastic ties in the past but even with...
  5. davidd31415

    How to control voltage when powering two DCmotors (not simultaneously)

    Yes, the failed open failure mode is worrisome. I've planned to limit the maximum output voltage at the power supply outputs to protect against this case. The problem with larger conductors is that anything larger than 18 AWG become impractical due to space available for wire routing, wire...
  6. davidd31415

    How to control voltage when powering two DCmotors (not simultaneously)

    Thanks Keith, Reasoning is to perform tests per specifications. Losses vary as ambient temperature surrounding devices under test change. Standard procedure has been to control the voltage at the power supply output terminals and offset it slightly to ensure the voltage at DUT terminals is...
  7. davidd31415

    How to control voltage when powering two DCmotors (not simultaneously)

    itsmoked, 1. The H-bridge is composed of four relays. 2. I am running one of two motors at a time with one power supply and one H-bridge. I'd like to sense voltage in one of five ways depending on which of the five modes is active... 000 - M1 off, M2 off - sense at power supply output 100...
  8. davidd31415

    How to calculate voltage drop in conductors?

    GeekEE, Thanks that's what I was looking for. IRstuff, Thanks for the table links. I'll remember they're in this thread.
  9. davidd31415

    How to calculate voltage drop in conductors?

    Ok, How about resistance per length as a function of wire diameter? How can I calculate that?
  10. davidd31415

    How to calculate voltage drop in conductors?

    I've been using this 'nomograph' to estimate voltage drop in conductors: http://www.kepcopower.com/nomomax.gif How would I calcualte voltage drops with equations? Is this something burried in Maxwell's equations? Thanks
  11. davidd31415

    Mounting accelerometers on DUTs during vibration durability tests?

    Thank jimkinney, Interesting thread but I am interested in where to place the control accelerometer, not how to mount it. I found this: http://archive.evaluationengineering.com/archive/articles/1006/1006control_accelerometer.asp I'm interested in a similar discussion related to sinusoidal...
  12. davidd31415

    Mounting accelerometers on DUTs during vibration durability tests?

    Is anyone familiar with the practice of mounting accelerometers on DUTs during vibration durability tests? I've been hearing conflicting (and rather passionate) views on if this is acceptable from a few different people. I'd like to find discussion of this subject haven't found one so far...
  13. davidd31415

    Details of magnetic mounting of fixtures on electromechanical shakers?

    The benefit I see is similar to that provided by magnetic accelerometer mounts. Setup and teardown times would be reduced. If fixture can not be coupled to the shaker with a rigidity similar to what is achieved with fasteners it would not be acceptable though.
  14. davidd31415

    Details of magnetic mounting of fixtures on electromechanical shakers?

    I've seen "magnetic mounting" systems, such as those integrated by Technomagnete and I'm wondering if anyone has heard of these being used to mount fixtures on electrodynamic shakers? The two concerns I see are the magnetic field of the mounting equipment interfering with the shaker operation...
  15. davidd31415

    Opinions of Omega's wireless devices- do you calibrate them yourself?

    Does anyone have experience with Omega's wireless transducers? I'm looking at the temperature, relative humidity, and pressure transducers to possibly replace chart recorders and keep a history of laboratory test equipment environments. I'm concerned about how well the OPC Server software...
  16. davidd31415

    Meausing voltage across a shunt resistor with an oscilloscope

    IRstuff, when you say "incidentally coupled to the AC mains," do you mean that the circuit may be coupled to the hot or neutral ? I'm unclear of the difference between the "actual and real" AC grounds. Would you mind elaboarting? Thanks, David
  17. davidd31415

    Meausing voltage across a shunt resistor with an oscilloscope

    Hi, I am trying to measure the voltage across a shunt resistor with an oscilloscope (actually, one of Yokogawa's 'ScopeCorders'). Since a DC current flows through this resistor in two directions, neither end is at ground potential. Can this voltage be measured with a single voltage probe...
  18. davidd31415

    Is Websense filtering your access to eng-tips?

    I know sites can be added or removed by administrators but there is a central database and Eng-tips seems to be added and removed from it on a semi-regular basis. I've never seen Tek-tips added to it, however.
  19. davidd31415

    Is Websense filtering your access to eng-tips?

    My company's internet filter, Websense, denied access to eng-tips for a few weeks about a year ago. Now this appears to be the case again. Is this happening to everyone with Websense or is it just my company?
  20. davidd31415

    Looking for a power supply that can be modulated

    The modulating signal is a sinewave. The application is automotive testing (AC signal superimposed on DC to simulate battery and alternator). I have a few Kepcos, TCRs, and Xantrex supplies- I was hesitant to use them since there isn't a specification for output frequency. I'll try them...

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