Ramanathan SG, Sr. Scientist from National Aerospace Laboratories, Bangalore, working for 2 seater aircraft. Recently Procured Rotax 912iSc engine and EMU with Fuel pressure (BRP 664365) sensor kit.

When we tested fuel pressure sensor with fuel pressure input in out calibration lab facility, we found some differences in output voltage, refer the attachment and please comment on it.

Questions:
1. Why do there be the difference between expected & measured output? Is there any measure to correct it? Is it an acceptable difference, please clarify.
2. We brought sensor from Stock Flight Systems, Germany along with Engine Monitoring Unit (EMU evo). What is the serial number of the sensors? We didn’t find it on the sensor.
3. Could you forward the detailed specification of BRP 664365 sensor?
FuelSensorCalibrationReport.pdf (You do not have access to download this file.)
  • Re: Fuel Pressure output difference

    by » 4 months ago


    The Sender is advertized as 0 to10bar = 0.5 to 4.5 volts.
    or 0bar = 0.5v plus 0.4v for each additional Bar.
    The Note #1 Formula should be VDC = 0.5 + (Bar *0.4)
    The (-1.0) is shifting the value by 0.4v

    Your 0 to 5bar "Expected" should be... 0.5, 0.9, 1.3, 1.7, 2.1, 2.5
    That puts you within ~0.05v across the board or well under 2% of full scale.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    whertzel1@yahoo.com
    Clicking the "Thank You" is appreciated by all.

  • Re: Fuel Pressure output difference

    by » 4 months ago


    Thank you for your reply.

    But i found a mismatch in the description mentioned in EMU system manuals (attached snap of it) and Sensor Troubleshoot manual (attached snap of it).

    1. EMU manual mentioned 0 to 10 bar = 0.5 V to 4.5 VDC
    2. Sensor Troubleshoot guide describes 1 bar = 0.5VDC and so on (refer snap attached)

    Please clarify about these difference.
    Also, we didn't find the sensor serial numbers on the sensor, please comment on it.
    EMUUserManual.JPG (You do not have access to download this file.)
    FuelSensorTrobleshootmanual.JPG (You do not have access to download this file.)

  • Re: Fuel Pressure output difference

    by » 4 months ago


    Notice that 0.5 to 4.5volts shown in the chart is for 1 to 11 bar ABSOLUTE, Not Gauge pressure.
    The sender is 0.5 to 4.5v = 0-10 bar GAUGE.
    Both scales are identical and explain why your readings are off by 1 bar.
    When the fuel lines are depressurized the pressure is Zero Bar Gauge or 1 Bar Absolute.

    Gauge Pressure relative to the Differential Manifold Pressure (MAP) is what you want to display with this engine.
    If your Sender is not of the Differential type with a second fitting to measure MAP pressure, you will need to configure the display to take the MAP into consideration, otherwise the fuel pressure display will vary with changes in the throttle.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    whertzel1@yahoo.com
    Clicking the "Thank You" is appreciated by all.

  • Re: Fuel Pressure output difference

    by » 3 months ago


    Thanks for making things clear.

    We understood that Sensor's Full-Scale Accuracy is 1%. Please confirm this value.

    We have carried out the Sensor Calibration & integration testing with EMU (Stocks System). I need your comments on the obtained Measured Sensor Output Values (VDC). Is it acceptable as per sensor output characteristics?

    We observed the Gauge Pressure on EMU display, in which we found the value is 1 bar higher, we understood that is because of Atmospheric Pressure. Please confirm, is it correct?

    Test-set-up and results are detailed in attached. Need your feedback on observations.
    ToRotaxCalibrartionData.pdf (You do not have access to download this file.)

  • Re: Fuel Pressure output difference

    by » 3 months ago


    Everything looks reasonable to me.
    It is accurate enough to be useful for the purpose intended.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    whertzel1@yahoo.com
    Clicking the "Thank You" is appreciated by all.

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