REFLECTOR: Dynon fuel pressure

Mon Apr 2 17:42:17 CDT 2012

I knew we had to be on the same track Brian!  I'm not the electron 
pusher you but I venture into that realm on occasion.

It looks like the Dynon supplied sensor is a VDO 360-003, 0-80PSI, 
10-180 ohms and case ground

I'm going to try a VDO 360-410, 0-80PSI, 10-180ohms, with a ground lug. 
separate connections for ground and signal.

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Dynon fuel pressure
From: Brian Michalk <michalk at awpi.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 04/02/2012 03:59 PM

> Oh. Actually we love the same thing.
>
> Yes. I agree. For any sensor you give me, it needs a minimum of two
> wires. One for voltage reference (ground) the other for signal.
>
> Using the chassey for signal return is asking for trouble.
>
> On 4/2/2012 4:20 PM, Scott Derrick wrote:
>> I love grounded sensors and have used them in instrumentation for
>> years in avionics( Space3 Shuttle, B1-B, etc..) and commercial
>> systems. But I expect that what ever I connect the sensor to, will
>> provide me with the sensor ground along side the data wire(amp. volt,
>> freq., etc).
>>
>> I completely agree that using power ground for sensors is B.A.D.
>>
>> Now Dynon actually provides the ground connections on the EFIS and EMS
>> but then provides shitty cheap ungrounded(meaning the ground path is
>> the bus(power) ground. Then when you tell them your having problems
>> they say your ground path from the engine to the instrument is bad.
>>
>> I swapped out the crappy Dynon provided ungrounded oil temp sensor
>> which was pathetically inaccurate, with a GRT grounded(ground lug on
>> sensor run to EMS) and now I get a smooth acurte reading unaffected by
>> voltage or amperage changes on the power bus.
>>
>> VDO is the manufacturer of the fuel sensor sold by Dynon. They make a
>> grounded sensor in the same PSI range, I need to find out if the
>> resistance is the same across its pressure range of 80 PSI. Or install
>> a GRT grounded sensor, but that sensor is only rated to 30 PSI and my
>> system is capable of producing 32 PSI. I think that would be OK but???
>>
>> Scott
>>
>> -------- Original Message --------
>> Subject: Re: REFLECTOR: Dynon fuel pressure
>> From: Brian Michalk <michalk at awpi.com>
>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> Date: 04/02/2012 12:49 PM
>>
>>> Back in my instrumentation days, the classes taught that "grounding" is
>>> really a misnomer. There are two type of common voltage, referred to as
>>> "ground."
>>> The first is power grounds. This is for lights, motors, alternators and
>>> that sort of stuff. The other type is for instrumentation. The sensor
>>> either generates a small voltage potential, or somehow moderates a
>>> voltage or current.
>>>
>>> I hate grounded sensors. They mix the power return path with my
>>> sensitive acquisition system that I take great pains to keep noise free.
>>> When the mfg. provides these, they contaminate all sorts of things
>>> causing ground loops, induced voltage, and possibly injected RF noise.
>>>
>>> I don't consider temperature probes where the body is grounded to the
>>> engine case for example to be a problem. In that case, the acquisition
>>> sensor checks for a voltage drop across the temperature probe, which is
>>> a high impedance sensor, and thus does not contaminate my sensitive
>>> acquisition voltages. It is still a current loop and that make it
>>> susceptible to noise because the current that went from the acquisition
>>> system to the probe, and into the engine case has to magically find its
>>> way back to the acquisition system somehow. The problem is that we don't
>>> know the return path, and that's the problem.
>>>
>>> Okay off my sandbox. Can you put a voltmeter on the sensor? Do you get
>>> the same results with everything turned off except the Dynon?
>>>
>>> On 4/2/2012 11:43 AM, Scott Derrick wrote:
>>>> I'm having an issue of a false high fuel pressure readingon my Dynon
>>>> EMS.
>>>>
>>>> I came within minutes of removing the fuel pump to see if the high
>>>> pressure reg was dirty or the recirc outlet was clogged. A 5 hour job
>>>> just to uncover the pump?
>>>>
>>>> I happened to be testing the installation of a replacement capacitive
>>>> fuel probe and noticed the fuel pressure was reading 10 psi and the
>>>> engine was off! I played around with re-grounding the sensor(Dynon has
>>>> a serious Achilles heal because they use ungrounded sensors) to see if
>>>> that would alleviate it but no joy.
>>>>
>>>> Anybody else have this issue?
>>>>
>>>> I'm thinking of switching to a GRT sensor as they are 1/2 to 1/4 the
>>>> price of Dynon's and most are grounded.
>>>>
>>>> Scott
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>>
>
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