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  • Re: Oil Pressure Sender - Rotax P/N 456-180

    by » 9 years ago


    Roger and Rob
    Thanks, I don't think I have an overheating problem for my sensor, it's the old VDO one that many people complain about and even Rotax have accepted wasn't very good and my gyro hasn't a cowling. I'm seriously thinking about a remote sensor but I don't like the idea of running a hose across the engine bay that'll be under pressure (all be it a low pressure). It's just another potential leak.

    I priced up the kit today.
    In France it's 250euros for the sender, 98 euros for the cable and 120 euros for the new gauge.

    Does anyone else have similar prices???

    Mike G

  • Re: Oil Pressure Sender - Rotax P/N 456-180

    by » 8 years ago


    Hi Ian and others

    I have been attempting to findout the actual pressure verses current relationship for the current rotax pressure sensor PN456180
    I am familiar with the rotax graph showing 4ma is 0.75bar and 20ma is 10.75bar which is confusing because of the linear axes shown.
    I have recently confirmed that dynons skyview sensor charactorization for this sensor is 4ma is 0 bar and 20ma is 10bar.
    Their charactorization is slighty non linear because of a parasitic 10k pullup resistor at their sensor input that cannot be removed.
    They are sure this is correct as they are told that PN456180 is identical to the previous honeywell unit.
    Has anyone confirmed that 20ma is 10bar or 10.75 bar?
    I think Ian mentioned that 0.8bar was 4ma as was 0 bar?
    If this is the case maybe the sensor cannot measure below 0.75bar and just shows 4ma between 0 and 0.75 bar?

    I think dynons assumption that the sensor is 4ma = 0bar and 20ma =10 bar is the most sensible, but I would still like to know the manufacturers spec of what it really is.
    I suspect it is a Keller pn PAA-21Y, but I cannot find precise specs whish clearly would resolve the issue.

    Doug

    Thank you said by: Ian Rees

  • Re: Oil Pressure Sender - Rotax P/N 456-180

    by » 8 years ago


    Hi Doug,

    The Rotax manuals are quite clear about the scaling, although the scaling on the axis is in error.
    4mA = 0.75 Bar
    20mA = 10.75 Bar

    As you may know, 4 to 20mA is an industrial standard for the processing industry. Pressure senders are readily available with this current output. However, the Rotax sensor sets 4mA to 0.75 bar rather than 0 bar as an offset. I don't think your Keller part number matches this range but is actually, 4mA = 0 bar.

    It means the sensor is probably not available from Keller with this non standard range (except via Rotax).
    You can test this quite easily, turn your engine instruments on, but do not start the engine. The oil pressure is 0 bar. What does your oil pressure gauge show, 0 bar or some positive pressure which corresponds to 4mA from the sensor.

    You can also measure the current output in this configuration with a simple multimeter measuring current. (Use the 400mA scale, not 10A scale on common Fluke brand meters). Mine measured just under 4mA.
    This means 0 bar to 0.75 bar reads 4mA since 0.75 bar is the bottom end of the scaling.
    I hope this helps.

  • Re: Oil Pressure Sender - Rotax P/N 456-180

    by » 8 years ago


    Hi
    Ian

    Yep I am familar with 4/20ma current sensors, being a retired electronic engineer and having designed interface equipment for them in the past.
    Your belief, based on rotax docs is the following
    The sensor reads 4ma for pressures between 0 and 0.75bar, then increases linearly from 0.75bar at 4ma to 20ma at 10.75bar
    Is this correct?

    If so, dynon asserts that because rotax documentation says the keller sensor is identical to the honeywell sensor, and the honeywell sensor is 0 to 10bar, then the rotax docs are inconsistant, and they have interfaced the keller sensor based on 0 to 10bar.
    I have been dealing with dynon and checked their sensor charactorization, and it is indeed 0 to 10bar.
    The consequence of this if the sensor is indeed 0.75 to 10.75bar is that the dynon will underread with the error getting worse as you read lower pressures. This will have been the case on dynon skyview equipment since the new sensor was introduced.
    Therefore, I am keen on seeing whether the pn456180 has indeed got the 0.75bar offset.

    I understand you have checked that the pn456180 outputs 4ma between 0 to 0.75bar. Are you aware of anyone who has checked the other end of the scale, ie at 20ma. Is this 10.75 or 10bar?
    Unless this is done, you cannot be sure that the linear gradient is correct. Unfortunately I dont have the pressure equipement to check this.
    Because I have a dynon skyview and dynon currently believe the sensor is 0 to 10 bar, I am keen on resolving the inconsistant info from rotax on the electrical equivalence of the honeywell sensor to the keller sensor compared to the transfer function grapgh with the incorr ct xaxis and the 0.75bar offset.

    Regards
    Doug

  • Re: Oil Pressure Sender - Rotax P/N 456-180

    by » 8 years ago


    Hi Doug,

    I understand exactly your concern. It is why I started this post over one year ago. (I am also an electronics engineer, so we are both looking for the same info).

    Please re-read my previous post. My experiment was to measure the current with the engine off. The result was 4mA = 0 bar.
    So we know one point on the graph. We do not know what the current is at 0.75 bar.

    If you read the earlier posts in this topic, I also asked the question about scaling,
    4mA = 0.75 bar
    20mA = 10.75 bar.
    Additionally, the sensor is linear between these limits.

    Check the reply, #10724 Rob Seaton came back with the answer is 4mA = 0.75 bar 20mA = 10.75 bar.
    This was about 13 months ago.

    I assume that Rotax data graphs and Rob wouldn't both be wrong, so until someone can prove otherwise, I am listening to Rotax and Rob but I do not have the pressure test equipment to validate the scaling, same as you. Therefore, we cannot prove it to Dynon to solve with 100% certainty.

    I did my research like you and found no-one makes such a calibrated sensor which casts the doubt over if it is a "Special" to match the earlier sensor calibration ????

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