Rotax 3 pin oil sender

[danny_galaga]

Just verifying that this sender unit on the oil pump being 3 pins is temp AND pressure. If not, what is it? And what is this type of plug called so I can buy one?

[skippydiesel]

Don't recognise it but most likely just pressure - temperature sensor is on the other side

Edited May 28, 2023 by skippydiesel

[onetrack]

Danny, not being pedantic, but it's called a sensor, not a sender. Parts people will be pedantic about this. The sensor (P/N 456180) measures oil pressure only, and I would have to say the plug is a Rotax special, and it only comes with the Rotax harness assembly, P/N WH-00096.

 

The following links will assist you ....

 

https://www.google.com/url?sa=i&url=https%3A%2F%2Faquila-aviation.de%2Fwp-content%2Fuploads%2F2019%2F08%2FSI_912_030R0_SI_914_031R0_OilPressureSensors.pdf

 

http://www.dogaviation.com/2016/02/wiring-of-rotax-456180-oil-pressure.html

 

Edited May 28, 2023 by onetrack

[IBob]

Note that if you have steam gauges, you cannot connect this newer type of sensor to the older style VDO gauge.
The correct steam gauge is this one:
https://www.aircraftspruce.com/catalog/inpages/cps15-06649.php?clickkey=64183

[danny_galaga]

4 hours ago, IBob said:

Note that if you have steam gauges, you cannot connect this newer type of sensor to the older style VDO gauge.
The correct steam gauge is this one:
https://www.aircraftspruce.com/catalog/inpages/cps15-06649.php?clickkey=64183

That is the gauge I have, and the plane this came out of has the same gauge. I'm puzzled why there seem to be three pins. Is one for pressure and one for a light?

[IBob]

It is what's called a current loop device, they commonly come in 2 and 3 wire versions and are an industry standard. Instead of behaving like a variable resistor, it puts out a current between 4 and 20mA. This one has a span of 10bar, so 0bar = 4mA and 10bar = 20mA.
The 3 wires are 0V and 12V to power it, and the third wire is the 4-20mA signal.

The reason for using current as a signal is that it can be connect with a short or a very long wire and it makes no difference. Voltage, on the other hand, will drop with a longer connection, due to the resistance of the wire, giving an inaccurate reading.
However, the reason for the change in these Rotax sensors was that the old VDO sensors had an unacceptable failure rate.

[Kyle Communications]

The new sensors also had a unacceptable failure rate especially for about 400 bucks each. They went away from the Honeywell one to a German one...starts with a K...something like Keller. Not sure how relaible the new ones are. I have had a Honeywell fail and I put a VDO resistor style in but I remote mounted it so take out the hammering they get from the crankcase. I now remote mount even the electronic sensors. You can see it next to the CDI module the silver one is my fuel pressure sender it is a 0-5V electronic type not the 4-20ma type

 

[rgmwa]

11 minutes ago, Kyle Communications said:

 They went away from the Honeywell one to a German one...starts with a K...something like Keller. 

 

 

Kavlico

Edited May 29, 2023 by rgmwa

[facthunter]

Putting it near the reduction gear would have to be one of the worst Places. IF you put a stethoscope or even a broom handle on the motor and to your ear, you will hear noises that will upset/ alarm you greatly.  Nev

[danny_galaga]

Well for now all I want is a connector for it. At the moment, that wh part number doesnt get me any closer to handing over my readies. Although after searching around I found out the sensor is from Honeywell so maybe I can pursue it that way. Perhaps through Digi-Key 

[danny_galaga]

Is this what the plug looks like? Of course these guys are out of stock. What the hells wrong with just using spade terminals, dammit...

 

https://jaydeeautocables.com.au/products/honeywell-pressure-sensor-connector-kit-hps3-k

 

[onetrack]

Danny, this looks like the same connector and you can get it from a Victorian company.

 

https://www.efihardware.com/products/2330/Motorsport-Series-Connector-For-TI-and-Honeywell-Pressure-Sensors

[danny_galaga]

9 hours ago, onetrack said:

Danny, this looks like the same connector and you can get it from a Victorian company.

 

https://www.efihardware.com/products/2330/Motorsport-Series-Connector-For-TI-and-Honeywell-Pressure-Sensors

Cool, will order that now 🙂

[danny_galaga]

Next question of course is what is the pin-out of this sensor?

[skippydiesel]

10 hours ago, onetrack said:

Danny, this looks like the same connector and you can get it from a Victorian company.

 

https://www.efihardware.com/products/2330/Motorsport-Series-Connector-For-TI-and-Honeywell-Pressure-Sensors

FYI - this sort of plug, with the silicone seal, has been causing intermittent erroneous readings on pressure sensors.

The reason seems to be, the seal is too good and does not allow for rapid changes of air pressure (like you might get in climb out) causing the sensor reading values to drop (in a climb).

If you are concerned with intermittent pressure drops, the test is simple - remove the seal and see if your pressures remain more consistent.

A permanent solution may be to cut a slot in the seal (still get some benefit from it) or if practical drill a small hole in the plug housing ie reduce the efficiency of the seal.

[danny_galaga]

I don't understand why it would do that, but will bear it in mind if I do get fluctuations 🙂

[IBob]

1 hour ago, skippydiesel said:

FYI - this sort of plug, with the silicone seal, has been causing intermittent erroneous readings on pressure sensors.

The reason seems to be, the seal is too good and does not allow for rapid changes of air pressure (like you might get in climb out) causing the sensor reading values to drop (in a climb).

If you are concerned with intermittent pressure drops, the test is simple - remove the seal and see if your pressures remain more consistent.

A permanent solution may be to cut a slot in the seal (still get some benefit from it) or if practical drill a small hole in the plug housing ie reduce the efficiency of the seal.

That's an interesting one, Skippy.
Given that 10,000ft sees approx 30% drop in air pressure, if altitude is the problem you would see approx 1/3 bar error at that height...not much, given that my oil pressure normally sits over 5bar.
 

[skippydiesel]

32 minutes ago, IBob said:

That's an interesting one, Skippy.
Given that 10,000ft sees approx 30% drop in air pressure, if altitude is the problem you would see approx 1/3 bar error at that height...not much, given that my oil pressure normally sits over 5bar.
 

This information came from The Rotax Owners Forum. (see below)

 

The bulletin is from Dyon but these connector are common  - I have been having intermittent low fuel pressure reading on TO/Climb out. It is possible that this information is pertinent to my problem in this area.

 

https://www.dynonavionics.com/bulletins/support_bulletin_120414.php

 

[IBob]

Ah right, Skippy, that would be much more of an issue: the oil pressure unit is 0 to 10bar, mine sits 5 to 6,  but the fuel pressure is 1/3bar or less, so if the unit is not correcting for altitude, you would see little or no fuel pressure at 10,000'.
I have seen the same problem now, twice, with fuel pressure steam gauges, where the builder has not removed the shipping plug from the gauge body.
 

[skippydiesel]

52 minutes ago, IBob said:

Ah right, Skippy, that would be much more of an issue: the oil pressure unit is 0 to 10bar, mine sits 5 to 6,  but the fuel pressure is 1/3bar or less, so if the unit is not correcting for altitude, you would see little or no fuel pressure at 10,000'.
I have seen the same problem now, twice, with fuel pressure steam gauges, where the builder has not removed the shipping plug from the gauge body.
 

Well I pretty much tried everything - was on the verge of purchasing a new Rotax  fuel pump (to replace the new on the engine) when I saw this notice. Went straight to the Sonex, checked the fuel pressure sensor plug, YEP!! other than colour looks identical. Have removed silicon (easy) seal, but have yet to test fly.

[danny_galaga]

I don't see how a fully sealed oil pressure sensor is going to be effected by outside air pressure...

[IBob]

Danny, these sensors are differential: they should measure the difference between the oil (or fuel) pressure on one side, and atmospheric pressure on the other.

Your oil pressure is atmospheric pressure + pump pressure, and is measured against atmospheric pressure.
So as you climb, the atmospheric pressure falls, but the differential pressure remains the same, so you continue to get an accurate reading.

But

 

If the sensor is sealed on the atmosphere side, then the atmospheric pressure is falling as you climb on the oil pressure side, but remains the same on the 'atmosphere' side. So you get an increasingly inaccurate reading.
And in the case of Skippy's fuel pressure reading it would make a huge difference.
 

[skippydiesel]

27 minutes ago, danny_galaga said:

I don't see how a fully sealed oil pressure sensor is going to be effected by outside air pressure...

You are may be  correct, regarding the oil pressure sensor (which may not be sealed against atmospheric pressure) as it is registering significantly higher pressures than a fuel pressure sensor.

 

I am well out of my experience comfort zoned here but understand that most (all?) of this type of sensor, essentially compares/adjusts for changes in  atmospheric pressure , so that the liquid pressure it is measuring is not added/subtracted from. Therefore the sensor must  have access to atmosphere

[IBob]

That's correct, Skippy. Think of it as a diaphragm, with one side to atmosphere, the other to oil (or fuel) and it is measuring the deflection in the diaphragm.
The key element is that oil pressure is atmospheric + pump pressure, so you are measuring that against atmospheric pressure.
So as you climb, the atmospheric pressure should decrease on both sides of the diaphragm, but the differential pressure (and diaphragm deflection) remains the same = accurate reading.
If, however, the atmospheric pressure falls as you climb on the oil/fuel side, but remains at ground level pressure on the other side (due to being sealed) then you get an increasingly inaccurate result.

[skippydiesel]

This principal  is vey well illustrated by this suppliers 3 tank level/capacity measuring products; https://www.safiery.com/tanks all of which require "access" to atmospheric pressure. (FGS don't mention aviation if you are making contact.)

 

 

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