MGL Avionics User Forum

The Westach Quad in my Glasair is showing OP that is 20 psi low versus a mechanical. Glasair first flew April of 1990.

MGL has the only 4 function gauge that I could find and the docs indicate that I can hook up just about anything to the TP-4. So I arranged to pick up one at OshKosh. Looks like the "details" though are gonna be a problem. I was planning on re-using the Westach OT and OP senders. The OT will work, but the OP won't. After some forensic dissection of some of the wire harness, I discovered I have a 4 wire oil pressure transmitter; power, ground, signal and what is the fourth????

My current mounting location limits me to a transmitter that is about 1" in diameter.

I don't want to pay the cost of a TSO'd unit like the UMA.

I'm considering a Dwyer 628-10-GH-P1-E1-S1 which uses 10-30 VDC as input and outputs 4-20 ma and has a 3' pigtail for about $98. Hmm, but maybe not a good choice cause temp specs are only 0-200 deg F.

A slightly more expensive option is an SSI Technologies P51-100-G-B-P-5V-000-000 which uses 8-30 VDC as input and outputs 1-5v and uses a Packard connection for about $157. Temp range for this one is -40 - 125 deg C.

I would have more options if I had a 5VDC power source available. Research shows that the automotive performance world uses lots of pressure sensors for data acquisition, but they all use a 5VDC power source.

Any ideas?

Then I also have to figure out how to integrate the magnetic current sensor. Where I was planning on putting it, I have the alternator output wire just a 1/2" away.

Thanks,
Lowell

Did some more reverse engineering on the Westach quad guage and some more research on pressure transmitters.

The Westach gauge does provide 5VDC to the oil pressure transmitter. So confirmed that I can't use old transmitter cause I no longer have a source of regulated 5VDC and I have no wiring diagram for me to figure out if the transmitter could be integrated with the MGL TP-4.

I wrote off the Dwyer transmitter as the temp specs were marginal.

Mouser Electronics was the only place I could find that would sell me a single SSI Technologies transmitter, but that unit only came with a Packard style electrical connector which involves more research and cost to get one of those connectors.

Went back to looking at the UMA transmitters. A non TSO'd unit, N1EU100G requires a regulated 5VDC and goes for $150+. Won't work for me. Automotive performance parts sellers list 100 psi transmitters for $35 to $60 - they also require 5VDC supply. I considered going this route and installing a 12vdc to 5vdc converter, but in the end decided against it.

UMA T1EU100G is internally regulated accepting an input voltage of 9-16VDC. It has a 1.5" diameter body which will just barely fit in the space I have to work with. So ordered it from Spruce for $200+.

Hopefully my postings will help if anyone else has these types of questions.

Lowell

Uncovered more information about the UMA pressure transmitters. Lot of inconsistent information out there on different websites.

When I received the T1EU100G it came with a spec sheet. Spec sheet said transmitter should only be used with a UMA indicator that can provide a regulated 9-12 VDC. Well, my bus voltage with the alternator online is 14.2 VDC. So am I gonna smoke the Tx or will I have output errors?

The Spruce catalog specs the Tx as having an input 9-16VDC and says the Tx in internally regulated.

UMA also manufactures an N1EU100G - so what is the difference between the N and the T versions? I spoke with a rep at UMA. They said that the N and T versions are exactly the same, the T version for TSO just comes with paperwork for another $50. Both transmitters accept input voltage of 9-16VDC. A couple of websites say that the input voltage for the N version is supposed to be 5VDC. Like I said there is inconsistent info out there.

So I wasted $50 by buying a TSO'd unit that I don't need.

Lowell