ClearNav Instruments

ClearNav Variometer => CNv Discussion => Topic started by: xcnick on June 12, 2020, 04:44:58 PM

Title: TE adjustment
Post by: xcnick on June 12, 2020, 04:44:58 PM
I flew in still air and successfully adjusted for my installed TE probe. However I wrongly thought I only had to switch to electronic TE in the menu and then adjust the electronic TE. Do I have to cap off the TE pneumatic when using electronic TE? Or maybe connect it to static? As it was, a pull up in still air made the vario show massive down that could not be adjusted out when set to electronic.

thanks
nick
Title: Re: TE adjustment
Post by: xcnick on June 13, 2020, 07:07:05 AM
I also have the airspeed showing 12/13 knots when in the hanger. I imagine I should find a way to zero this out.

I have tested all pneumatic as having no leaks but worry about this airspeed error and calibrating the TE. Is there anything else I should set? I feel the zero of the vairio is off because I can get a slight up in audio when the altimeter is loosing feet.
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 13, 2020, 07:04:51 PM
I flew in still air and successfully adjusted for my installed TE probe. However I wrongly thought I only had to switch to electronic TE in the menu and then adjust the electronic TE. Do I have to cap off the TE pneumatic when using electronic TE? Or maybe connect it to static? As it was, a pull up in still air made the vario show massive down that could not be adjusted out when set to electronic.


Switching between probe and no probe is strictly electronic.  In "no probe" mode, CNv simply ignores the TE pneumatic input.

FWIW, I use "no probe" all the time.  I have a triple probe source, I use the TE for my mechanical vario.  I get better TE compensation off "no probe" than I do with the TE.
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 13, 2020, 07:07:59 PM
I also have the airspeed showing 12/13 knots when in the hanger. I imagine I should find a way to zero this out.

I have tested all pneumatic as having no leaks but worry about this airspeed error and calibrating the TE. Is there anything else I should set? I feel the zero of the vairio is off because I can get a slight up in audio when the altimeter is loosing feet.

The zeroing procedure is as follows:

1.  Let the instrument warm up at least 20 minutes.
2.  In completely calm air...
3.  Go to the "tools" menu
4.  Press/hold down arrow button, and then push GO (while holding down arrow).
5.  "Hidden tools" will now be visible.  There are several screens here, the one you want shows raw pressure sensor values and includes an option for zeroing (push GO).
6.  After zeroing, exit the hidden tools menu or just restart the vario.

If using the pointer display, at step 4 press both buttons together, then follow instructions on the display to get to hidden tools.

Title: Re: TE adjustment
Post by: xcnick on June 17, 2020, 05:50:50 AM
Thanks, zeroing out the airspeed did not fix my electronic TE. In this video I try to adjust the electronic TE and the results are not what I expected.

https://www.youtube.com/watch?v=9o6bI--JhmU
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 18, 2020, 05:14:21 PM
I use electronic compensation routinely, with unshared triple probe sources.  It works great.  Didn't have to make any adjustments.

So: what sources are you using for pitot and static, and what instruments are they shared with, if any?

In general, any instrument that adds volume, or flow, is going to be a problem. 
Title: Re: TE adjustment
Post by: xcnick on June 18, 2020, 07:04:38 PM
Airspeed, CNv, and CN map. Static and Pitot is shared. Static under the wing on both sides. TE in the tail and shared with no one.

On a computer screen one can see the vario. It is set to electronic in my video, does it make any sense to anyone? When set to use the probe it doesn't go crazy like this.
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 21, 2020, 08:25:45 AM
You'll get better results with the TE probe on that setup.

Unshared, co located, probe based pitot and static sources are the only kind that work reliably for no-probe TE.  You can (maybe) get away with sharing pitot with your ASI, but it will cause some transient issues.  If you are flying a lot at very high altitude, the problem becomes more difficult (higher TAS, more kinetic energy to compensate).

I landed remotely yesterday, took an aero retrieve in dead air.  I whiled away my glide to the home drome tuning my TE system and checking the polar in CNv.  I have a triple probe set up, and I am currently using "No-Probe" TE.  I ended up at +7%.  It is essentially perfect. 
Title: Re: TE adjustment
Post by: xcnick on June 21, 2020, 08:57:02 AM
Thanks, I can hook up a second static source. However it is so drastically wrong in the opposite direction this seems like too small a swing at it. Taking the sensors to 0 so my airspeed is zero had no effect. I am thinking I have a wire crossed or a dip switch backwards, or at least that kind of error. I will do a second static and report back.
Title: Re: TE adjustment
Post by: xcnick on June 24, 2020, 06:32:16 AM
No change. I have zeroed the sensors, separate static and pitot... nothing.

I found the wiring diagram for the phone cord to the CN, but I can't find how the phone cord from the display to the ADC should be wired.

Are there any dip switches?
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 24, 2020, 08:24:35 AM
No dip switches.

Not sure what's up with the blinking display, but that's got to be a power or hardware (electrical connection) problem.  Check the external stuff first.  If no external fault can be found, call Rex @ Williams. 

As far as the TE problem... I think there's a problem in the pneumatic system.  It isn't obvious to me where this is, but I'd be looking for something major.  I'd start with verifying that all the connections were what I thought they were (mixed up static and TE would explain some of this, maybe).   Check for leaks.  I find a syringe, an old vario flask and a box of T connectors and tubing work well for pneumatic troubleshooting.  The purpose of the flask is to provide some extra volume so movement of the syringe doesn't break things.  Compare vario IAS to ASI. 
Title: Re: TE adjustment
Post by: xcnick on June 24, 2020, 08:41:16 AM
The pneumatic system was tested, sensors zeroed, separate pneumatic tried. Rex confirms the blinking "is common. Nothing broken. Just annoying." It goes crazy when using electronic compensation, not the installed TE.
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 25, 2020, 04:25:13 AM
Ah, that's why I don't see the blinking.  Then it should go away with a software update.  Don't laugh!  We're flight testing 3.8 now.

Do you get sensible airspeeds in flight from CNv?
Title: Re: TE adjustment
Post by: xcnick on June 25, 2020, 06:06:27 AM
I did not go to that info page while flying on electronic TE. When testing the pneumatic system, the airspeed on the CNv was the only a couple of miles faster than my airspeed, is that good enough?



Title: Re: TE adjustment
Post by: xcnick on June 25, 2020, 06:29:08 AM
Actually the test was done with it set on probe. It didn't occur to me it could be different on electronic.
Title: Re: TE adjustment
Post by: Evan Ludeman / T8 on June 25, 2020, 08:57:43 AM
The IAS indicated is a function of pitot and static pressure, independent of TE compensation selections and adjustments.  If it showed values significantly at odds with your ASI, then that might provide some clues as to what is going on. 

"Electronic" TE is very sensitive to errors in the pneumatic sources.  Errors result from 1) non-ideality in the source location (under wing statics...), 2) excess capacity and flows in the system associated with mechanical instruments (the static side of a mechanical ASI is a problem for sure, the pitot side less so, but still noticeable), 3) leaks, whether intentional (say, for a mechanical netto vario) or not, 4) timing differences between pitot and static due to location, parasitic capacity differences, impedance differences. 

Except in the case of unshared, probe mounted pitot and static, it's generally best to use a TE probe.  The only problem here is that sharing a mechanical vario with a pressure transducer vario on same TE probe raises hell with the electronic vario.  I realize this is intensely frustrating... I've been down this road myself! 

One final long shot: are you certain the whole system is dry?  Accumulated moisture in any of the pneumatic lines can and will cause some very strange behavior (personal experience). 
Title: Re: TE adjustment
Post by: xcnick on June 25, 2020, 10:14:05 AM
Water in the tubes would also cause problems when set to use the probe, or so I would think.

No other vario, just ASI is shared and when taken out of the system there was no change.

Under the wing static is no good? Great, the manual says there are problems with the nose statics, history has shown the boom static hates water, and I always fly with water.

I understand electronic TE is more sensitive to installation, but this much? I made the video to emphasis just how whack it is when set to electronic TE.

Looking back it would have been better just to buy another ADC and give it the old “remove and replace”. Then if it acted the same, go through the installation.