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G5 with GAD 13 OAT

RV6_flyer

Well Known Member
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I am planning on adding a GAD 13 to my two G5s and GMU 11 in my RV-6. I have the GAD 13 and connector kit on order and the plan at this time is to use a probe from an old RMI microEncoder for OAT. The GAD 13 documentation (G5 Manual) says that it will work with an AD590 probe and Garmin lists two less expensive probes that should work.

Since the RMI microEncoder is out of production but they do have PDFs documents online, others that are electrical savy should be able to fabricate their own probe (PDF page 49 & 50 / doc page 51 & 52) for about 1/3 of what the non-Garmin probes cost. Digikey sell the part for the temp sensor for less than $20 and the cap plus a piece of brass tubing to protect does not add that much to the cost.

I will report back IF my homemade RMI OAT probe does not work and will spend the $100 for one of the recommended non-Garmin probes. I have all the parts to make a probe in my hangar except the brass tube. Amazon delivers it on Monday.
 
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please do report back

I have been thinking about doing this as well. Please let us know what your findings are.
 
Does it matter where you place the otp on the plane? I was thinking of mounting the gad13 in the tunnel next to the magnetometer on the shelf. The probe would be near the rear of the plane. I didn't see any warnings or placement instructions with the probe or the gad13.
 
Does it matter where you place the otp on the plane? I was thinking of mounting the gad13 in the tunnel next to the magnetometer on the shelf. The probe would be near the rear of the plane. I didn't see any warnings or placement instructions with the probe or the gad13.
Hello,

Even if you are not using a Garmin GTP 59 outside air temperature probe with your GAD 13, the installation guidance for this OAT probe in the G3X Installation Manual should be useful for determining probe location.

You can mount the GAD 13 almost anywhere convenient inside the fuselage or wings, but we don't recommend mounting it next to the magnetometer.

Thanks,
Steve
 
Hello,

Even if you are not using a Garmin GTP 59 outside air temperature probe with your GAD 13, the installation guidance for this OAT probe in the G3X Installation Manual should be useful for determining probe location.

You can mount the GAD 13 almost anywhere convenient inside the fuselage or wings, but we don't recommend mounting it next to the magnetometer.

Thanks,
Steve

Steve:

Is there a distance recommendation for the GAD 13 from the GMU 11? Something like greater than one-foot or more.
 
Steve:

Is there a distance recommendation for the GAD 13 from the GMU 11? Something like greater than one-foot or more.
Hello Gary,

The installation manual specifies that "Electrical devices drawing less than 100 mA current" should be a minimum of 2 feet from the GMU 11.

Thanks,
Steve
 
I have been thinking about doing this as well. Please let us know what your findings are.

I got the GAD 13 with 'homemade' OAT prop installed and powered up today for the first time.

My 'homemade' OAT prop (same as used my Rocky Mountain Instrument microEncoder and microMonitor) is working. Initial OAT read 1 degree F higher than my digital thermometer in my hangar. Note TAS upper left hand corner, OAT lower left hand corner, and density altitude lower right hand corner of the upper G5 and on the lower G5 "No Wind Data" in the upper left hand corner.

2019-09-30-14-29-33-6300.jpg


Now I need to pick stuff up, finish paperwork, and go test fly.

Thank you Steinair for getting this to me so quickly.
 
G5 with GAD 13 in fight photo

I finally flew my new GAD 13 today. Garmin equipment installed are two G5s, GMU 11, and GAD 13. I am using a homemade OAT probe using the instructions from RMI microEncoder assembly manual. (page 49 has assembly instructions) Everything worked inflight just like I expected. The surprise I had was when I was on downwind at pattern altitude (1,000 AGL) I had 18 Kts crosswind almost 90 degrees to the runway. I could see the windsock on the ground indicating calm winds.

2019-10-02-08-56-56-1670.jpg


When on the ground, Density Altitude is displayed above the altimeter setting but it disappears when flying.

Note to Garmin G3X Experts: Feel free to use the image(s) I post(s) any way you like that shows your G5(s) in my aircraft.
 
Gary,
Thanks for your excellent write-up of this little money-saver.

The copy of the RMI instructions that I pulled offline (Rev D, 1/1/04) specifies a ".1FFD" ceramic cap with the first F looking like it has been changed (different font).

Is that supposed to be picofarad or microfarad? I am not familar with FFD.
 
Gary,
Thanks for your excellent write-up of this little money-saver.

The copy of the RMI instructions that I pulled offline (Rev D, 1/1/04) specifies a ".1FFD" ceramic cap with the first F looking like it has been changed (different font).

Is that supposed to be picofarad or microfarad? I am not familar with FFD.

0.1 micro Farad is the value recorded in my PAPER copy dated Rev B, 12/30/1994. Sometimes the electronic PDF copies does not handle the special characters correctly.

Here is the image of a capacitor like the one that I used.
2019-10-08-13-03-42-0060.jpg


Here is the image of the temperature transducer like the one I used.
2019-10-08-13-03-13-3350.jpg
 
thanks for the write-up and pics Gary.
I have the same set-up waiting for an end-of-the-season (rather call that a slow-down...) install, presently sporting a single G5.
Though also on my parts to be installed pile a Davtron OAT and, lucky me, a GNX375 and GAD29...

Wonder what it would take to have an AP function, 2 servos and a control panel? Anyway to go without the control panel due price/space/install work considerations?
 
My entry into this Inexpensive Temp Probe Derby is based on a thin film platinum device from, you guessed it, Digikey. Suprisingly, they are cheap, accurate, but also very tiny.

I thought some of you might be interested in another way to git'r done.

What I have now is basically a GTP 59 probe clone.

I bought a bunch of TE pn 223-1820's which are 1kohm units. To get the required 500 ohms for the GAD 13, I put 2 in parallel to make what is effectively a single 500 ohm device. One connection goes to GAD13 pin 6. The other side of the device goes to pin 3 AND 8 with a jumper.

If you are all about precision( i am), or have a long run or are using thin wire, consider using 3 wires. In this case, run 2 separate wires from one side of the device to pins 3 and 8 of the GAD 13 - no jumper. This is the way the GTP 59 is installed. It only makes a very small difference. Spruce's 24 gauge x 3 shielded cable or similar might be a good choice for probe cable.

Tested accuracy was pretty good. Distilled water ice temp was spot on 32F. Boiling water temp was ~207.9F. The calculated temp for my pressure altitude was 209.33F. So, off by ~1.5F, quite good. Less than 1 degree C. This will correspond to a small fraction of a degree at flight air temps. Testing was done using 2 short wires and jumper.
ron
 
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Hi Peter

The sensors I used have leads, so the mounting would be similar to using the AD590- .

The easiest mounting for most applications would be to solder the device to the cable wires and then install it in a small piece of tubing, maybe brass tubing as the OP described.

In my case, the sensor location will be a well ventilated wheel well and mounting will be by simply cable clamping in place.

BTW, The specs for these RTD devices are generally much better than the cheapo grade AD590 ($20). I bought 25 for of these RTD's for ~$40.

Also, this approach may be a satisfactory sub for the GTP 59 to use with the G3X. Someone should look into that, since, in that case, there is no alternate probe source for the GPT 59 $$$.

Ron
 
Density altitude..

I wonder if Garmin don't want density altitude to be displayed when airborne as it could then be confused with real altitude...which is a shame as knowing the density altitude can be really helpful at times...

This is a great thread as getting reliable OAT is important (particularly to avoid icing)...and the Garmin (albeit TSO solution) is expensive...
 
I just got my G5 to work with a GAD 13 and an EDMO 655 OAT probe. I went with the less expensive probe $89 from ACS. I had to install a CAN Terminator at each end. I'm very happy with these results.
 
Digikey Temp Probes

Copied Cumolo's sensors from Digikey. Works Great!.
Don't forget to update the G5 to the latest firmware, or it may not recognize the GAD13
 
"No Wind Data"

Any ideas why this happens/displays? I have GAD 13 feeding into G5 and getting OAT and TAS, but no wind speed and direction.

Thx!

I got the GAD 13 with 'homemade' OAT prop installed and powered up today for the first time.

My 'homemade' OAT prop (same as used my Rocky Mountain Instrument microEncoder and microMonitor) is working. Initial OAT read 1 degree F higher than my digital thermometer in my hangar. Note TAS upper left hand corner, OAT lower left hand corner, and density altitude lower right hand corner of the upper G5 and on the lower G5 "No Wind Data" in the upper left hand corner.

2019-09-30-14-29-33-6300.jpg


Now I need to pick stuff up, finish paperwork, and go test fly.

Thank you Steinair for getting this to me so quickly.
 
"No Wind Data"

Any ideas why this happens/displays? I have GAD 13 feeding into G5 and getting OAT and TAS, but no wind speed and direction.

Thx!

In the picture above, the aircraft is parked on the ground. When stationary, GPS TRK and GPS Ground Speed are invalid, and the system cannot calculate winds aloft.

You also need a GMU 11 since heading is also required to calculate winds aloft.

Steve
 
Extra's?

I bought a bunch of TE pn 223-1820's which are 1kohm units.

Any chance you still have some of these laying around? I would take a few if you need to unload them, rather ordering from Digikey. I am planning on installing a GAD13 with my G5's and would like to give this a shot.

Also, any more details on the wiring and mounting? Is it simply taking 2 of them, twisting the leads together, attach the wires, and mount it somewhere?

I was thinking of making my current 307PS style probe mount/tube do double duty with these (since you can't share probes among instruments, and this one runs to the JPI).
 
I have Garmin GTP59 Oat probe w/G3X that I believe is bad.
I dont want to shell out $450 for new Cert probe if I can use another brand probe
I do not have a G5, my G3X system uses a GSU73 ADHARS unit (old one)
Hard to imagine that there isn't a cheaper experimental type version that would work.
Any ideas appreciated
 
I have Garmin GTP59 Oat probe w/G3X that I believe is bad.
I dont want to shell out $450 for new Cert probe if I can use another brand probe
I do not have a G5, my G3X system uses a GSU73 ADHARS unit (old one)
Hard to imagine that there isn't a cheaper experimental type version that would work.
Any ideas appreciated

I don't have it installed yet but I went with the Davtron probe, part number C307PS. That is what Stein sells with his OAT "kit."

Not as inexpensive as the home made stuff in this thread, but not $450 either. Not positive it will work in your application. I have a GAD 13 to use it with.
 
Sensors

Mile High Relic
Quote:
Originally Posted by socal View Post
I have Garmin GTP59 Oat probe w/G3X that I believe is bad.
I dont want to shell out $450 for new Cert probe if I can use another brand probe
I do not have a G5, my G3X system uses a GSU73 ADHARS unit (old one)
Hard to imagine that there isn't a cheaper experimental type version that would work.
Any ideas appreciated
I don't have it installed yet but I went with the Davtron probe, part number C307PS. That is what Stein sells with his OAT "kit."

Not as inexpensive as the home made stuff in this thread, but not $450 either. Not positive it will work in your application. I have a GAD 13 to use it with.

I don't think an AD590 based probe such as the Davtron C307PS will work on a G3X system. It requires a GTP59 platinum resistor type probe. The GAD13, however, is made to work with either type of probe.

The probe I described up thread is electrically the same as the Garmin GTP59 and should work with either the G5/GAD13 or the G3X by hooking it up as a GTP59.

BTW, the GTP59 can be easily tested by ohming it out with a common ohm meter. Look for a resistance of ~500 ohms between one of the wires and the other 2. Also, near 0 ohms between those other 2.

The GTP59 probe sensor is just a 500 ohm platinum resistor with 2 wires connected to one side and the 3rd wire connected to the other side.

Ron
 
Untainted123
Extra's?
Quote:
Originally Posted by Cumulo View Post
I bought a bunch of TE pn 223-1820's which are 1kohm units
.

Any chance you still have some of these laying around? I would take a few if you need to unload them, rather ordering from Digikey. I am planning on installing a GAD13 with my G5's and would like to give this a shot.

Also, any more details on the wiring and mounting? Is it simply taking 2 of them, twisting the leads together, attach the wires, and mount it somewhere?

I was thinking of making my current 307PS style probe mount/tube do double duty with these (since you can't share probes among instruments, and this one runs to the JPI).

To: Untainted123

Sorry I forgot to respond to your PM months ago. I looked for those little critters and don't remember where they are, otherwise you would have had a couple in your hand by post. If you have since ordered them, you know that they are not much bigger than a fly speck, easy for this old guy to loose.

Experiment:

Since the subject of enclosing these tiny sensors in a probe and mounting it came up, I have another idea. If there is a place under the wing aft of the spare and tank that is accessible, why not just glue those little specks to the skin on the inside in the middle of a bay? The skin temp will be within a fraction of a degree of OAT. And no extra snags sticking out to be a problem. They'er cheap. Might be the way to go.

Ron
 
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To: Untainted123

Sorry I forgot to respond to your PM months ago. I looked for those little critters and don't remember where they are, otherwise you would have had a couple in your hand by post. If you have since ordered them, you know that they are not much bigger than a fly speck, easy for this old guy to loose.

Experiment:

Since the subject of enclosing these tiny sensors in a probe and mounting it came up, I have another idea. If there is a place under the wing aft of the spare and tank that is accessible, why not just glue those little specks to the skin on the inside in the middle of a bay? The skin temp will be within a fraction of a degree of OAT. And no extra snags sticking out to be a problem. They'er cheap. Might be the way to go.

Ron

Ron, no problem, I ended up ordering some from Digikey. I ended up making this:
IMG_7342.jpg
IMG_7340.jpg

I installed it in my wing access panel and pulled a 22/3 shield wire back to the cockpit, hooked to my GAD13. Seems to work great. I went with 2 sensors, 1k OHM, and wired them together, giving the 500ohm range needed.

Read this thread for the details of how to do that. Basically, 2 wires go to the power side, and one to the other side (the sensors are agnostic, just choose the same side on both if using 2).

I agree though, I should have just glued them somehow to a wing rib or in the wing root; I ran some numbers on OAT vs TAS, and you basically have to be off by a lot to make the readings bad.

In other words, there has been discussion about the OAT picking up exhaust heat, or the sun or whatever, and that is all valid, but even a 10*F error either way works out to a 1kt difference in TAS, which was the main thing I was looking to get a read out on my G5 of (and winds aloft data), so I shouldn't have stressed as much as I did trying to get that stupid wire out there under the wing and routed through holes I can't see back to the cockpit. Putting it in the wing root under the fairing should work just as well and be more than accurate enough for our purposes.
 
I don't think an AD590 based probe such as the Davtron C307PS will work on a G3X system. It requires a GTP59 platinum resistor type probe. The GAD13, however, is made to work with either type of probe.

The probe I described up thread is electrically the same as the Garmin GTP59 and should work with either the G5/GAD13 or the G3X by hooking it up as a GTP59.

Ron

Is it just a Garmin thing that they want to sell their GTP 59 with the G3X instead of the GAD 13? The OAT section of the G3X manual says in part:

"In a G3X Touch system with one or more G5 displays but no ADAHRS units, a GTP 59 can optionally be connected via the GAD 13 temperature probe adapter. If the system is later expanded with the addition of one or more ADAHRS units, the GAD 13 may be retained, or the GAD 13 may be removed and the GTP 59 connected to the #1 GSU 25 ADAHRS unit. Refer to the G5 installation manual (190-02072-01) for GAD 13 information.

If the Davtron probe works with the GAD 13, and the GAD 13 puts the OAT data on the CAN bus, is that an alternative to the GTP 59 connected directly to the GSU 25?

The G3X manual doesn't say you can use 3rd party OAT probe with the GAD 13, but the G5 manual does show that option.
 
Is it just a Garmin thing that they want to sell their GTP 59 with the G3X instead of the GAD 13? The OAT section of the G3X manual says in part:

"In a G3X Touch system with one or more G5 displays but no ADAHRS units, a GTP 59 can optionally be connected via the GAD 13 temperature probe adapter. If the system is later expanded with the addition of one or more ADAHRS units, the GAD 13 may be retained, or the GAD 13 may be removed and the GTP 59 connected to the #1 GSU 25 ADAHRS unit. Refer to the G5 installation manual (190-02072-01) for GAD 13 information.

If the Davtron probe works with the GAD 13, and the GAD 13 puts the OAT data on the CAN bus, is that an alternative to the GTP 59 connected directly to the GSU 25?

The G3X manual doesn't say you can use 3rd party OAT probe with the GAD 13, but the G5 manual does show that option.

Well, Garmin is not in the business of selling Brand X probes, so I would not expect them to elaborate on the configuration that you mentioned, but I see no reason why it would not work just fine.

On the other hand, if one is planning on a G3X from the start, a simple substitution of the GTP 59 by a home brew RTD probe connected directly to the GSU 25 would be the way to go. Then no need for a Gad 13 either.

The thing to keep in mind with wiring the substitute is that the single connected wire is to be the (orange) wire of a GTP59 described in the Garmin docs. The other two will be the blue and white(or yellow) of the GTP 59. Which is which doesn't matter.

Ron
 
On the other hand, if one is planning on a G3X from the start, a simple substitution of the GTP 59 by a home brew RTD probe connected directly to the GSU 25 would be the way to go. Then no need for a Gad 13 either.

Ron

Definitely, but I'm not sure I'm up for building my own when I already have the GAD13 and Davtron probe on hand.

Such are the perils of discovering better solutions after already purchasing something.
 
If the Davtron probe works with the GAD 13, and the GAD 13 puts the OAT data on the CAN bus, is that an alternative to the GTP 59 connected directly to the GSU 25?

Yes, you could do this, although I imagine most people wouldn't bother for a brand-new installation since it would weigh more. For a G5 installation that is later upgraded to a full G3X system it makes a little more sense in terms of preserving already-installed equipment and wiring.
 
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