Coolant Temperature

[Bo_Hannington]

I have a Rotax 912ULS in my Foxbat aircraft, and since I wanted to use all 3 GP inputs on my D180, I have replaced the 2 resistive Rotax CHT sensors with J type thermocouples.
I have used one of these Rotax CHT sensors as a coolant temperature sensor.

My installation manual lists 4 types of sensor to choose from, including the Rotax 801-10-1 sensor as type 4.

However, when I try to select this sensor type, I only have choices 1,2, and 3, but not 4. Using type 1 the Coolant temp is reading about 90 degC instead of 24degC ambient.

How can I get the right sensor type?

 

[dynonsupport]

Which of our products is this, and which version of firmware is it running?

UPDATE: Actually, it looks like you've just found a bug in our latest firmware. That sensor type should be available as documented, but it somehow did not get documented. It's now on our list of bugs to fix.

 

[Bo_Hannington]

Thanks for your reply. To answer your first query, I have Flightdek D180, and it is running V01.08.

So, if this is a bug to be fixed, what is the approximate timescale by which this will occur?

 

[dynonsupport]

We're going to try to squeeze it into our next firmware update, which is due soonish. We don't have a firm release schedule available yet though.

 

[alan_milner]

Hi, I also have this exact same issue on an EMS D10. It has installed the standard Rotax water temp sensor which is essentially the Rotax oil temp sensor 801-10-1 which works well for oil temp as sensor type 4.

However, I have connected the water temp to GP3 and only have sensor types 1-3 in the setup config for GP3.

I'd be happy to install a beta while the sensor is accessible and I can check the calibration if that will help.

Alan. (EFIS D100, EMS D10, Europa 912ULS. UK)

 

[alan_milner]

Hi

V3 looks very nice - a huge amount of new features, well done Dynon. I'm flight testing at the moment and the engine is running a bit hot. So the recording of engine data will be very very useful.

I am struggling with the Rotax Collant Temperature sensor though. I have the standard oil sensor in the coolant line. This is connected to GP3 and I can now choose snesor type 4. But the reading comes in at over 300 °C.

If I disconnect the sensor I get -99 on the display.

Am I missing something? Any help would be most welcome as I really could do with monitoring the collant temp.

Alan. UK, Europa XS, Rotax 912ULS, EMS D10, EFIS D100

 

[dynonsupport]

What do you mean by "the standard oil temp sensor in the line?" Do you mean a Dynon oil temp sensor or a Rotax oil temp sensor?

Do you have a pull-up resistor going to the +5V line? This is definitely required for accurate readings.

 

[alan_milner]

Thanks for the quick reply.

It's a Rotax oil temp sensor 801-10-1 which is inserted into a boss in the water coolant piping. It is connected to the +5v line via a resistor and the other end is grounded. This sensor was supplied via a Rotax dealer in a coolant temperture kit for the 912ULS.

I presume I have selected the correct sensor type (4)?

Am I using the correct sensor for the Dynon?

I'll try connecting the same lead to the oil temp and CHT sensors to see what temperature comes back. Hopefully, I have just made a mistake with the wiring.

Alan

 

[dynonsupport]

As a sanity check to make sure we got this characterization right - at ambient outside temperature, with power off, measure the resistance on the coolant temperature sensor, and get back to us with the resistance and the temp you measured it at.

Also, Rotax sensor we support is for coolant temp is basically just another copy of the CHT sensor, and so it should look the same as the preinstalled Rotax CHT. Does it?

 

[josok]

Just to jump in, same problem here. Close but wrong readings on all other (1,2,3) sensor selections.
Resistance 1500 ohm at 16 celcius, just like the oil sensor.
Pull-up 1 k from 5 v : reading -99.
Please don't let us wait for the next update, can i have a patch please?

Regards,

Jos Okhuijsen

 

[josok]

Just to add to the confusion: I was running the engine today, and with the coolant sensor on 3, instead of Rotax 4 the temperatures seem to make sense, especially on the higher like 80-100 C range. My blind bat is that sensor 3 is actually 4, and somebody started counting the bits at 1 instead of 0

Regards,

Jos Okhuijsen

 

[dynonsupport]

Just to clarify - you are seeing the correct readings now, right?

 

[dynonsupport]

Jos,

We've run a unit here and can't find any problems.

120 ohm resistor into oil temp, type 4, 180 deg F, as expected.

120 ohm resistor into GP1, type 4, pulled up to the 5V excitation line with a 1K resistor, 178 degF, as expected.

The type 4 coolant looks like it works fine. I'd check your pull up resistor. Make sure it's 1K, and it's hooked to the 5V excitation line. Make sure the 5V excitation is working and is at 5V.

Please be aware that the 1K pull up really needs to be exactly 1K. It can throw off the numbers quite a bit. We use all 0.1% resistors inside the unit, and if you really want dead-on accuracy, you'll need to use one outside as well.

The coolant type 3 and type 4 are pretty close to one another at 70-80C. In fact, at 80C, they are exactly the same. So if coolant temp is working as type 3 at 80C but not as type 4 at 80C, I'm stumped. It works on my desk.

 

[josok]

Strange things happening,
as said, -99 if i select sensor type 4, close to true readings with sensor type 3 selected. Pull up is 995 ohms on my meter. I can switch between the almost good and -99 reading just by changing the sensor type back and forth.
anything i can do to clarify the situation on my side?



Regards,

Jos Okhuijsen

 

[alan_milner]

I performed some tests today and still have problems with coolant temperature on GP 3.

1) I can confirm the coolant sensor is identical to the Rotax CHT sensor. At about 21 degrees C the resistance is approx 1.2k, this is confirmed on both CHT sensors, the coolant sensor and the oil sensor.

2) I have GP1 and GP2 reading the Rotax CHTs - these work perfectly. If I connect one of the CHT sensor leads to the water temperature sensor then it reads about 21 degrees, which is correct - so the sensor works

3) I replaced the excitation wire, just incase. This is terminated in one of the 1k resistors supplied by Dynon and is connected to the end of the GP3 wire that clips onto the coolant sensor. With sensor type 4 selected it reads 999. If I disconnect the wire from the sensor, it reads -99.

4) Selecting other sensor types give numbers less then 100, but none seem appropriate.

Just a thought, did you test it on GP3 as well as GP1? Could the GP3 input on my unit be defective?

I will try a 120 ohm resistor and see what I get. I guess I could rip out the rotax sender/plumbing and use another type, it's just really bad timing

Also, the installation manual calls for a 1.21k resistor to the +5v circuit for the CHT sensors. I presume this is accurate? I just wonder why it differs to the pull-up resistor used for the coolant temp when it is the same sensor in use.

Thanks for your help.

Alan

 

[dynonsupport]

I tried it on all three GP inputs, but not with Rotax CHT1 and CHT2 defined on the other GP's. Maybe try it with those turned to something else? If there's a bug here, it's a tricky one.

 

[alan_milner]

Thanks for looking more. Maybe the unit has a problem.

Can you give me a resistance and expected temperature for the type 4 and one of the other sensor types. Then I'll put a resistor on and see what reading that gives.

The only part I haven't checked is the supplied harness, but that has been faultless so far for every contact on the EMS and EFIS.

Cheers

Alan

 

[dynonsupport]

120 ohms = 179 deg F on coolant temp (type 4) with a 1K pull-up.
1000 ohms = 76 deg F on coolant temp (type 4) with a 1K pull-up

120 ohms = 171 deg F on coolant temp (type 3) with a 1K pull-up.
1000 ohms = 68 deg F on coolant temp (type 4) with a 1K pull-up

 

[josok]

120 ohms = 179 deg F on coolant temp (type 4) with a 1K pull-up.
1000 ohms = 76 deg F on coolant temp (type 4) with a 1K pull-up

120 ohms = 171 deg F on coolant temp (type 3) with a 1K pull-up.
1000 ohms = 68 deg F on coolant temp (type 4) with a 1K pull-up

Probably a typo but where?

If it's tomorrow again too bad weather to first-flight, i'll do a new check and tell you exactly what i have at what GP, and maybe even change like carb heat or fuel pressure around between GP 1, 2 and 3.
He, that fuel flow sensor i have, the UMA diff sensor puts out a voltage, it's not resistance. Could that influence another GP input?

Regards,

Jos

 

[dynonsupport]

Whoops. Only one cut&paste typo I see:

120 ohms = 179 deg F on coolant temp (type 4) with a 1K pull-up.
1000 ohms = 76 deg F on coolant temp (type 4) with a 1K pull-up

120 ohms = 171 deg F on coolant temp (type 3) with a 1K pull-up.
1000 ohms = 68 deg F on coolant temp (type 3) with a 1K pull-up

As long as you don't put more than 5V into a GP input it shouldn't mess with the other ones. If you put more than 5V in, it will mess the others up for sure.