oil temp fluctuation

[Fgerr]

Thanks for the reply. For what its worth, I did replace the oil temperature sensor with a new VDO sensor of the original type (single wire). No change in behavior of the temperature readout - rock steady at low temperatures, with increasing second-to-second variability at operating temperatures of about +/- 3 degrees F. So, I think the problem is not due to sensor defect, per-se.
Fred

 

[fuzzflyer]

I have the exact same condition with Dynon 120 !!  I have had two Rotax engineers  look at the issue,  they state the Earth is fine on my Sting Aircraft, I added a second earth with no difference. (now removed) The UK agents are now offering to send me a replacement unit to try!  but are we just wasting our time here..  please respond Dynon. My problem has been from new 2010 ,and the problem mainly shows up on warm flying days when the temp goes into the yellow and touches around 115 the reading go haywire from red to green and back in split seconds.
I have also being" living with it"! But we need a solution .

I have also had the sender replaced .

 

[jaroberts2pe]

I have the same problem with my D180, and it is a new problem. The engine is a Lycoming 0-360 in a Lancair. Temps read solidly until this summer. Now the oil temp reads high and the higher it reads, the greater the fluctuation, so that on a recent flight it fluctuated between 234-260F. Until this summer the oil temp reading in normal cruise was rock solid at 192F (2 1/2 years.) Temp reading, like reported by others, is rock solid as temp climbs until reaching about 210, then small fluctuations increase as the apparent temp (judging by upper and lower reading) increases. Unlike other reports I also (recently) experience fluctuations in manifold pressure but only at high power/high altitude. Again, all readings rock solid for 2 1/2 years, nothing changed. Will clean and reattach all grounding straps to see if that helps.

 

[fuzzflyer]

It would be great to get some response from DYNON!
I will be contacting the UK agents again tomorrow . To see if there is any plan to solve this issue soon.

Poor show so far

 

[gteldp71i0]

fuzzflyer for whats its worth i had the same problem, changed sensors, renewed spade terminals at sensor heads etc with no joy only on further investigation further up the wiring loom there was a bad/dry soldered joint in the loom , resolderd and sensors are now solid, pig of a thing to find though

 

[fuzzflyer]

Hi All

Yesterday I had a VDO manual oil temp gauge fitted,trying to solve this fluctuation on the Dynon, I piggy backed a wire to the Dynon spade at the sensor but then the Dynon read 1 degree. The manual temp gauge was of course steady.
The problem I now have is the incorrect reading to the dynon effects the Tach, outer scale which indicates when ready to apply full power.

I wonder if anyone at Dynon could advise please, Like would putting a diode on the wire to the VDO gauge work?

 

[fuzzflyer]

So
I had the electronic engineer  look again at this issue  and he seems to think it is the 5.5 volts that dynon uses:  with the sensors being designed for 12volts:  apparently they cannot give the steady resistance needed is how I understood it. 
I have now disconnected out the oil temp on Dynon!! This has made the OIL PRESSURE more steady  but seems to read Higher!!  
I am  using the reliable Steam powered..until Dynon has this resolved.

Noted this, could you elaborate please, will this two wire unit fit into the rotax 912ul? how do we find it etc?
Thanks
Or should I call you?
If you prefer (if this is an LSA, this is not really a possibility) to use a different oil temp sensor, we have a list of two-wire oil temperature sensors that are compatible with Dynon's EMS, but not supplied by Dynon. Note that to make use of these sensors, you must have firmware v5.4.2 or later on your EMS. (Note - these sensors are not supported in SkyView.) The advantage of a two-wire sensor that you're no longer dependent on engine block ground path back to the EMS.

 

[fuzzflyer]

So
I had the electronic engineer look again at this issue and he seems to think it is the 5.5 volts that dynon uses: with the sensors being designed for 12volts: apparently they cannot give the steady resistance needed is how I understood it.
I have now disconnected out the oil temp on Dynon!! This has made the OIL PRESSURE more steady but seems to read Higher!!
I am using the reliable Steam powered..until Dynon has this resolved.

Noted this, could you elaborate please, will this two wire unit fit into the rotax 912ul? how do we find it etc?
Thanks
Or should I call you?
If you prefer (if this is an LSA, this is not really a possibility) to use a different oil temp sensor, we have a list of two-wire oil temperature sensors that are compatible with Dynon's EMS, but not supplied by Dynon. Note that to make use of these sensors, you must have firmware v5.4.2 or later on your EMS. (Note - these sensors are not supported in SkyView.) The advantage of a two-wire sensor that you're no longer dependent on engine block ground path back to the EMS.

Sorry for the short-sighted response above. On further research, we've noted the same thing that you have: that the identical sensors ostensibly go through the same ground path through the engine. There's only a slight difference in the way that they're wired, and they're equivalent. An interesting experiment that you could perform, if you're able is to simply take the wires at the CHT and Oil Temp sensors themselves and swap them (if this is an LSA, you really can't do this without the manufacturers' support, unfortunately, because you can't make changes to the aircraft that aren't in the maintainance manual (and then only with an A/P or LSA repairman)). But the idea here is to see whether the bouncing moves with the sensor or the input?

And, note that your experiment doesn't disprove a ground issue of some kind, as the alternator current being passed through the resistance of the ground path is what generally causes noise in sensors, not just the resistance of the ground path. The fact that the noise goes away when the alternator stops is actually a strong indication that it is actually a ground issue, but we're still a bit baffled how it can affect one sensor more than another.

 

[dynonsupport]

Well, that instrument could be less sensitive to grounding issues, but for different reasons than you mention above. That neither here nor there: we do remain convinced that there's a ground issue here. Unfortunately, proper grounding can get a bit complicated and depends on the particular wiring scheme of the airplane. But, if you want to prove to yourself that there's a non-ideal ground in the airplane, hook up a voltmeter between the engine sensor case (it's ground) and the case of the Dynon (also ground) while the engine is running and you're observing the behavior on the screen. You should only see a few millivolts there, but I suspect you'll see 10s of millivolts. Anyway, for those of you experiencing this, a question to help us investigate:

What are the EXACT temperatures of BOTH the CHTs and Oil temp when you're in the range of temperatures that you see this issue?

Also, as another test, you can try reduce the load on the aircraft to demonstrate. Try turning on and off high current draw items like landing lights, heated pitots, and so on. If those change the temp, that's a good proof that changing loads is the issue. If you don't have any big loads like that, transmitting on the radio is probably the next big thing to observe.

 

[fuzzflyer]

  I flew yesterday and need to mention that the CHT and oil pressure readings are all over the place also. so getting an EXACT reading is not possible, also FYI, the amps read anywhere from -1 to +10 amps,

That was flying with the VDO manual gauge connected and the dynon oil temp disconnected.  VDO was very steady  at all temps.



I will get the engineer to do more grounding checks and install a heavy wire to the Dynon bus.?

 

[dynonsupport]

The fact that amps is also fluctuating ALSO points to a non-optimal grounding situation.

Again, I'll re-iterate some of the tests you can do to determine whether this has to do with voltages induced because of a non-optimal ground:

First, do the fluctuations go away when you turn off your engine?

Next, you can try reduce the load on the aircraft to determine if the load has an effect. Try turning on and off high current draw items like landing lights, heated pitots, and so on. If those change the temp, that's a good proof that there is a grounding issue. If you don't have any big loads like that, transmitting on the radio is probably the next big thing to observe.

Finally, if you can, hook up a voltmeter between the engine sensor case (it's ground) and the case of the Dynon (also ground) while the engine is running and you're observing the behavior on the screen. You should only see a few millivolts there, but I suspect you'll see 10s of millivolts. 

The solution isn't a cut and dry prescription, and really needs to be engineered. I can practically guarantee that a different Dynon unit will not fix the issues. It needs to be addressed at the airframe level. One question you might ask your manufacturer is whether this is something they see on other airplanes of your same type.

 

[jnmeade]

Has anyone tried a capacitor from the sensor lead to ground?
Has anyone tried a two-lead sensor with the ground lead going straight to pin 16 or 17 of the D37 connector?

 

[jakej]

Has anyone tried a capacitor from the sensor lead to ground?
Has anyone tried a two-lead sensor with the ground lead going straight to pin 16 or 17 of the D37 connector?

1. No - never have seen the need to do that.

2. Yes, a 2 wire probe with ground going back to Dynon is more 'robust' IMO

Jake J

 

[jnmeade]

Has anyone tried a capacitor from the sensor lead to ground?
Has anyone tried a two-lead sensor with the ground lead going straight to pin 16 or 17 of the D37 connector?

1. No - never have seen the need to do that.

So, you think the vibrating needle movement is not possibly noise on the line or you think that if it is noise the cap won't cure it?

2. Yes, a 2 wire probe with ground going back to Dynon is more 'robust' IMO 

Jake J

You're saying you've tried the two wire probe and it's better in your opinion, or you're speculating that it might be - I'm not sure which you are saying. Sorry for being obtuse. If it's better, I'll just get some. If that is the case, ground them all to which pin, or does it matter?

 

[dynonsupport]

A capacitor will not fix the issue. While the right capacitor in the right place will reduce the fluctuations you see, the number on the screen will be artificially high, and will vary as you change the load on your aircraft alternator.

Unless this is an ELSA, you cannot change to a two wire sensor without permission from the aircraft manufacturer.

 

[jnmeade]

Yes, mine is an ELSA and I'm prepared to do about anything to get it working right. If I get a fix and the manufacturer likes it, you can bet there will be a lot of pressure for them to issue a fleet LOA.

Since I can legally put a 2 wire lead on, which ground pin should I hook it to?

I'm talking about a cap on the sensor positive lead. That is a DC line. How can the alternator have anything to do with it, unless we have AC noise on there, in which case, why won't the cap help, and why will a small cap pull up the signal voltage? I'm not an EE, as I'm sure you assumed. I'm just looking for answers.
What are the chances some computer chip or clock in the Dynon is generating a square wave that is not in sync with the the alternator output and that presents as noise on the Dynon ground lines?

 

[dynonsupport]

We've asked you to try things like turning off the engine or changing the load on the alternator to prove to yourself that it's a ground issue. Have you tried these?

The cap won't work because it averages the value. The ground issue can never lower the temperature reading, it can only raise it. This is not noise AROUND the correct value, it's all noise ABOVE the correct value. So as the ground causes an error, it's always equal to or above the real temp. Take the average of this, and the average is higher than the real temp. Plus, capacitors are not magic. Your issue is noise on the ground line, so hooking a cap to the positive line doesn't suddenly help. All electrical devices have at least one terminal, and where you hook the ground side of this would be critical as to if it did anything. Plus, the capacitor you would need would be HUGE because the changes in signals are small.

The issue is that the alternator produces current, and all currents involve a + side and a - side. The + side just isn't a factor because nothing in the sensor path uses that. The - side IS an issue, because the ground for the alternator, temp sensor, EMS, and battery are all shared. But no ground is perfect because we aren't using superconductors. So when the ground current tries to go from the alternator to the battery, it causes a voltage change along the ground cable due to ohm's law. Well, the EMS is trying to share that path and read the sensor value, but it has to assume a 0 volt change. If your ground is insufficient, there is more than 0V there and that causes an error. Thus, the alternator current has everything to do with this.

We have thousands of these units in the field, with very few issues. The issue is not inside the Dynon unit.

Hooking the ground wire of a two wire sensor up is easy. There are many free ground pins on the EMS wiring harness, and any one of them will work. So will grounding it to the EMS case or tray somehow.

Understand that we've been through this issue many times since we released our EMS products 6 years ago, and it's always a ground issue. It's hard to explain it, as it's a complex issue and tricy to wrap your mind around, but the ground between your engine and your EMS is critical to proper sensor performance.

Here are the third party two wire sensors we support. You'll have to look yourself to see if they meet the mounting requirements you have:

http://wiki.dynonavionics.com/Third_Party_Two_Wire_Oil_Temperature_Sensors

 

[dahugo]

Dynon Support,

I had the same issues, and instead of tracking down a minor ground issue, I bought the Westech 399S9 and installed it per instructions. Now my oil temp reading never goes above 75 degrees--I know the oil is getting to the right temperature and all other engine readings are normal.

Is there something else I need to do to make it work right? I mean, installation is not hard--one side is hooked to the same wire on the D180 and the other is grounded directly to the ground block 10 inches away.

Help please.

 

[Dynon]

dahugo - Did you switch to sensor type 9?

 

[fuzzflyer]

dahugo - Did you switch to sensor type 9?

dahugo - Did you switch to sensor type 9?

dahugo - Did you switch to sensor type 9?

dahugo - Did you switch to sensor type 9?

I see a post on the Rotax forum concerning this ongoing Oil temp issue: that there is a software fix available for the 120? Can't seem to get to Dynon here? can anyone offer advice on this fix? I have tried to download that file but my comp says file not found..
:-/