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Date: Mon, 22 Jun 2009 22:52:59 -0400
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From: "William Rumburg" <lancair403@verizon.net>
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Subject: Re: [LML] Re: VMS 1000 Fuel Pressure Transducer
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The Honeywell MediaMate fuel pressure transducer sold by VMS (JP 
Instruments) utilizes a plug-on Hirshman (right angle) connector which, as 
Brent points out, is a poor design considering the weak 50 mVDC output 
signal and potential for voltage drop across the connector. The Measurement 
Specialties replacement that I recommended employes a permanently connected 
2' cable, which virtually eliminates voltage drop; however, it's 2' length 
is too short and requires a connector to mate with the VMS-furnished four 
conductor cable (the wires furnished with a new $1,000. Oildyne pump and 
most FM/CD/MP3 players are also too short and require connectors). Utilize a 
four-circuit AMP free-hanging connector (Digi-Key p/n A1402/1431) 
(http://dk3.c.digikey.com/B092/p80221.pdf) and gold-plated pin/socket 
(Digi-Key p/n A1432/1434 (http://dk3.c.digikey.com/B8092/p80222.pdf)

Bill Rumburg
N403WR (Sonic bOOm)


----- Original Message ----- 
From: "Brent Regan" <brent@regandesigns.com>
To: <lml@lancaironline.net
Sent: Sunday, June 21, 2009 8:32 P
Subject: [LML] Re: VMS 1000 Fuel Pressure Transducer


>I had a similar experience as Bill  except it was the oil pressure
> sensor. Nothing gets you on the ground faster than a zero oil pressure
> alarm. Happened twice. The first time I replaced the sensor and the
> second time was about a month later. I figured it must have been a
> connection of the DPU so I replaced the cable, connections and even
> removed the DPU to verify proper function. I swapped fuel pressure and
> oil pressure inputs to be sure it wasn't a flaky A-D channel on the
> DPU.  After weeks of mucking about it turns out that the new sensor was
> flaky.  A call to JP got the "You installed it you bought it" response.
> My reply? Foxtrot Yankee.
>
> I never much cared for the Media Mate sensors because they used crummy
> "Faston" spade connections that treat millivolt signals like a junk yard
> dog so I decided to make something better.
>
> Understand that these types of pressure sensors use strain gages
> (resistors that vary with strain) in a Whetstone bridge configuration.
> The output is proportional to the input and the pressure applied,  or
> millivolts per volt of excitation per PSI of applied pressure. If at 50
> PSI and 5 volt excitation you get a 5 millivolt output then at 10 volt
> excitation you would get 10 millivolts at the same applied pressure.
> VM1000 uses 5 volt excitation.
>
> For the oil pressure I ended up selecting the Honeywell 19C series in
> 0-100 PSI range (19C100PG4K)
> http://sensing.honeywell.com/index.cfm?ci_id=140301&la_id=1&pr_id=145986
>
> and machining a backshell out of aluminum to accept a MIL Spec 4 pin
> connector. (see attached picture of the modeled assembly). You need
> access to a lathe and a mill for about an hour to make the backshell.
> The sensor was about $110 and the connector another $20.
>
> The fuel pressure sensor needs to have a 0-50 PSI range so the part
> number would be 19C50PG4K.
>
> The sensor has been installed for over 2 years without any problem.
>
> Any brave soul that wants to follow my footsteps to make their own
> backshell, email me and I'll send you a drawing, or better yet, the
> SolidWorks model.
>
> Regards
> Brent Regan
>


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