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Fuel Pressure output difference

  • ramguna84
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3 weeks 4 days ago #22979 by ramguna84
Fuel Pressure output difference was created by ramguna84
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?

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3 weeks 4 hours ago - 3 weeks 4 hours ago #23015 by Bill Hertzel
Replied by Bill Hertzel on topic Fuel Pressure output difference
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.
Last edit: 3 weeks 4 hours ago by Bill Hertzel.

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2 weeks 6 days ago #23028 by ramguna84
Replied by ramguna84 on topic Fuel Pressure output difference
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.

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2 weeks 5 days ago #23033 by Bill Hertzel
Replied by Bill Hertzel on topic Fuel Pressure output difference
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.

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