• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 725 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS127L01: cable length

Tommy Tzeng
Mastermind 6450 points

Part Number: ADS127L01

Hi Team,

The currently project uses the 2 CH line to connect to the IEPE sensor (model: 780B), and the wire material is used(as attached).

we would like to know how length the wire can be?

Can ADS127L01 still receive signals?

xdaq-600(1).pdf

780B-780C spec (99014)D.1.pdf

C111J3106A10SL30000.pdf

  • 0
    TI__Guru 51880 points

    Hello Tommy,

    This question is better answered by the IEPE sensor manufacturer, Wilcoxon.  However, I think you should be able to drive a 3 meter cable and get good results.

    I took a quick look on their web site, and they have an excellent application note that discusses the tradeoffs between signal frequency, sensor drive current, and cable length.  Here is a link to their application note.

    https://wilcoxon.com/wp-content/uploads/2018/11/TN22_Vibration-sensor-wiring-and-cabling_2018.pdf

    Figure 4 shows the relationship between maximum signal frequency and cable length for different excitation currents, assuming a typical cable capacitance of 30pF/foot.  I looked at your cable specification, and did not see a capacitance specification, but I would not expect it to be significantly different.  However, you should contact the cable manufacturer and ask for a cable capacitance per unit length to confirm the exact value.

    Per your schematics, you are driving the sensor at 4mA.  Referring to the Wilcoxon app note, Figure 4, and assuming you have a typical cable capacitance of 30pF/foot, you should be able to drive up to 10ft, or 9 meters of cable and support frequencies up to 100kHz.  Assuming you only need to support a signal frequency up to 14kHz (the 3dB bandwidth of your sensor), then the maximum cable length in this example would be  closer to 250ft, or 76 meters.  In addition, Figure 4 assumes a 5V peak signal.  Looking at your schematics, your full scale will be 3.3V peak, which further increases the maximum length of cable possible.

    If you have any specific questions regarding the ADS127L01, please reply to this e2e thread.

    Regards,
    Keith Nicholas
    Precision ADC Applications