X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 25 Apr 2014 07:55:19 -0400 Message-ID: X-Original-Return-Path: Received: from moutng.kundenserver.de ([212.227.126.130] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6845911 for lml@lancaironline.net; Thu, 24 Apr 2014 17:55:19 -0400 Received-SPF: none receiver=logan.com; client-ip=212.227.126.130; envelope-from=nick@beaglepup.info Received: from Asus8 (host86-168-252-43.range86-168.btcentralplus.com [86.168.252.43]) by mrelayeu.kundenserver.de (node=mreue004) with ESMTP (Nemesis) id 0MFfhh-1Wij3y0HWn-00EgLp; Thu, 24 Apr 2014 23:54:39 +0200 X-Original-Message-ID: <2AE5628CF8884F10B42E5683558ECEFA@Asus8> Reply-To: "Nick Long" From: "Nick Long" X-Original-To: "WILLIAM HOWIE" , "Lancair MailingList" References: In-Reply-To: Subject: Re: [LML] Re: VMS1000 pressure gauges on LNC2 X-Original-Date: Thu, 24 Apr 2014 22:52:36 +0100 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0083_01CF600F.E2CD6040" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 16.4.3528.331 X-MimeOLE: Produced By Microsoft MimeOLE V16.4.3528.331 X-Antivirus: avast! (VPS 140424-1, 24/04/2014), Outbound message X-Antivirus-Status: Clean X-Provags-ID: V02:K0:SqyGIIMfYZw+UtjmI27d/82+AZujnD2HKTCKsbPBxnt +gvu9T0lNZyo6x61OAKaJDNBkoGRUSWFV08iUonGzcI4KDOwo8 NgzULwjQc8+YnJYziX5gHvS7+5gcFBxudYegaoXOMdXd/I9Eop Pte00l1dg9LRdRiwIrrg6UIy++g8lGbQWp9ADn3OzX0AWDMpAP lFXDF8JDIP+Pb9CRAn2varFLdCH1ziFce76uoaoifzp35dV84/ 2/csGOpv9El96yVrzEIzgtwD3+YL8y6loiFyvmh06lRp9elHIu 759fxzGIcEB13iYWdp30/6pEfRZK3CjRGBWdrgYapksta2ANdm uOropEvqdm+XI8P8rLng= This is a multi-part message in MIME format. ------=_NextPart_000_0083_01CF600F.E2CD6040 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Bill, This is my understanding. There are 4 terminals on the transducer or sensor, marked 1 to 4. 4 =E2=80=93 5 V supply =E2=80=93 usually red wire 2 =E2=80=93 0 V Ground =E2=80=93 usually black wire 3 =E2=80=93 V1 out =E2=80=93 usually green wire 1 =E2=80=93 V2 out =E2=80=93 usually white wire The signal out is the voltage difference between V2 and V1. These = voltages are about 2 V, but the difference between then varies from 0 mV = to 50 mV in normal operation. The transducer seems to be a passive bridge network, or almost. V2 = varies with the pressure, and V1 is a reference that doesn=E2=80=99t = change with pressure. The important value is V2-V1. This is what the = VM1000 measures and uses to calculate the pressure. With the device powered up and with no pressure, , then V2 and V2 should = be the same, to within a mV. This is fairly simple to test, either in the aircraft or on the bench. = You could either use a voltmeter to measure them each accurately, or put = a voltmeter on a small range scale between them. If it passes that test then the next one is to see how the differential = voltage V2-V1 varies with pressure. This is a more difficult test but = you may not need to do it. By the time you have got this far, it may = well be clear where the problem lies. HTH, Nick From: WILLIAM HOWIE=20 Sent: Thursday, April 24, 2014 4:18 PM To: Nick Long=20 Subject: Re: [LML] Re: VMS1000 pressure gauges on LNC2 Nick: I have a IVP, and I had a indication of no oil pressure LAST WEEK I PUT A PRESSURE GAUGE ON THE OUTLET OF THE TRANSDUCER AND I HAVE OIL = PRESSURE. THE PROBLEM THEN IS WITH THE TRANSDUCER OR WITH THE CONNECTION FOR THE = DPU. I CAN'T FIND MY TESTING PROCEDURE FOR THE TRANSDUCERS, I was hoping = you could help me with this. Could you tell me you're testing procedure on the vision Microsystems = transducer. The pins are numbered one through four but I don't know where to apply = the 5 V and where to read the output. Thanks a lot Bill Howie Sent from my iPad On Apr 23, 2014, at 10:46 AM, "Nick Long" wrote: Hi Bill, Thanks for the info. I think you have done everyone a service and = it=E2=80=99s good to know you have some drop in replacements available = at half the price I have seen them elsewhere. If you don=E2=80=99t mind, though, I=E2=80=99m going to pursue my = ideas a bit further. I quite like the idea of using off the shelf = sensors and using the same one for OP and FP. There is also the = background thinking that the VM1000 is a bit old now and that rather = than building a solution around that, I could devise something with = general applicability. Over the holiday weekend I did some more investigation. I built a rig = in my workshop to pressurise the old sensors from my air line system* = and measure the resistance changes and the voltage outputs. The two = sensors gave the right voltage changes (50 mV and 100 mV for 100 psi) = but with horrendous offsets. The zero psi values were way out. So they = were working, but not actually any use. Then I checked the VM1000 panel by injecting voltages on the FP and OP = inputs. That did exactly what was expected, but now I also know what = common mode voltages it will cope with. Anyway, I have ordered some modern sensors with 0 to 5 V outputs and = I=E2=80=99m going to scale the outputs down to suit the VM1000. I will = let you all know how I get on. If I=E2=80=99m right, then I will have = something that should work with any other monitoring systems that are = out there. Yours, Nick *not as easy as it sounds because the sensors are NPT threads and my = system is completely and utterly the way it should be =E2=80=93 British = Standard Pipe thread. From: William Rumburg=20 Sent: Monday, April 21, 2014 4:43 PM To: lml@lancaironline.net=20 Subject: [LML] Re: VMS1000 pressure gauges on LNC2 Nick - The VMS1000 oil and fuel pressures were designed for the Honeywell = MediaMate, which produces 50mV DC full-scale output when excited with = 5VDC. The MediaMate, however, is inferior, antiquated technology and = outrageously overpriced.=20 A modern, high-quality replacement is the Measurement Specialties = US321. It also produces 50mV DC when excited with 5VDC; hence, it's an = electrically-DIRECT replacement for the MediaMate = http://www.meas-spec.com/downloads/US300.pdf=20 A problem, however, is that the VMS1000's combination of 5VDC = excitation and 50mV DC full-scale output is, apparently, rarely used in = industry; hence, I couldn't locate any US321's -in the needed pressure = range- for sale despite an exhaustive search. I contacted Measurement = Specialties last August and learned that they would manufacture them at = a cost of $140 each, with a minimum order of five. So I ordered five @50 = psi (fuel pressure for fuel-injected engines) and five @100 psi (oil = pressure). I ordered them with four foot pigtails to allow direct = routing to the DPU, with no intermediate connector. Attached is a photo = of them installed on my engine. If anyone is interested, I'm offering = the extra's for my price of $140 each. Bill Rumburg N403WR (Sonic bOOm) Hello Everyone, A few weeks ago we had a discussion about this, and I then went away = and checked my installation. After measuring the voltages I concluded = that the display unit is ok, but both the Oil Pressure and Fuel Pressure = sensors are not behaving. So then I looked into replacements. There was an interesting post = last September from Bill Rumburg about using sensors from Measurement = Specialities; the originals are Honeywell Mediamates. Bill was saying the OP and FP transducers are different in their = voltage vs pressure response by a factor of 2 and he was exploring some = alternative devices. But here is another idea. Why not just find a = sensor that gives the correct output for FP? The same sensor will give = 2x the reading if used for OP, but that can be scaled down by 2 with a = simple precision resistor network. If that is correct, and I=E2=80=99ve followed the previous = discussion correctly, then Digi Key have the very item we need: = http://www.digikey.com/product-detail/en/M3421-000006-100PG/MSP6892-ND/72= 6352 What do you think, people? Yours, Nick -------------------------------------------------------------------------= ----- -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html ------=_NextPart_000_0083_01CF600F.E2CD6040 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Bill,
 
This is my understanding.
 
There are 4 terminals on the transducer or sensor, marked 1 to = 4.
4 =E2=80=93 5 V supply =E2=80=93 usually red wire
2 =E2=80=93 0 V Ground =E2=80=93 usually black wire
3 =E2=80=93 V1 out =E2=80=93 usually green wire
1 =E2=80=93 V2 out =E2=80=93 usually white wire
 
The signal out is the voltage difference between V2 and V1. These = voltages=20 are about 2 V, but the difference between then varies from 0 mV to 50 mV = in=20 normal operation.
 
The transducer seems to be a passive bridge network, or almost. V2 = varies=20 with the pressure, and V1 is a reference that doesn=E2=80=99t change = with pressure. The=20 important value is V2-V1. This is what the VM1000 measures and uses to = calculate=20 the pressure.
 
With the device powered up and with no pressure, , then V2 and V2 = should be=20 the same, to within a mV.
This is fairly simple to test, either in the aircraft or on the = bench. You=20 could either use a voltmeter to measure them each accurately, or put a = voltmeter=20 on a small range scale between them.
 
If it passes that test then the next one is to see how the = differential=20 voltage V2-V1 varies with pressure. This is a more difficult test but = you may=20 not need to do it. By the time you have got this far, it may well be = clear where=20 the problem lies.
 
HTH,
 
Nick
 
 
Sent: Thursday, April 24, 2014 4:18 PM
Subject: Re: [LML] Re: VMS1000 pressure gauges on=20 LNC2
 
Nick:
I have a IVP, and I had a indication of no oil pressure LAST = WEEK
I PUT=20 A PRESSURE GAUGE ON THE OUTLET OF THE TRANSDUCER AND I HAVE OIL = PRESSURE.
THE=20 PROBLEM THEN IS WITH THE TRANSDUCER OR WITH THE CONNECTION FOR THE DPU. = I CAN'T=20 FIND MY TESTING PROCEDURE FOR THE TRANSDUCERS, I was hoping you could = help me=20 with this.
Could you tell me you're testing procedure on the vision = Microsystems=20 transducer.
The pins are numbered one through four but I don't know where to = apply the=20 5 V and where to read the output.
Thanks a lot Bill Howie


Sent from my iPad

On Apr 23, 2014, at 10:46 AM, "Nick Long" <nick@beaglepup.info>=20 wrote:

Hi Bill,
 
Thanks for the info. I think you have done everyone a service and = it=E2=80=99s=20 good to know you have some drop in replacements available at half the = price I=20 have seen them elsewhere.
 
If you don=E2=80=99t mind, though, I=E2=80=99m going to pursue my = ideas a bit further. I=20 quite like the idea of using off the shelf sensors and using the same = one for=20 OP and FP. There is also the background thinking that the VM1000 is a = bit old=20 now and that rather than building a solution around that, I could = devise=20 something with general applicability.
 
Over the holiday weekend I did some more investigation. I built a = rig in=20 my workshop to pressurise the old sensors from my air line system* and = measure=20 the resistance changes and the voltage outputs. The two sensors gave = the right=20 voltage changes (50 mV and 100 mV for 100 psi) but with horrendous = offsets.=20 The zero psi values were way out. So they were working, but not = actually any=20 use.
 
Then I checked the VM1000 panel by injecting voltages on the FP = and OP=20 inputs. That did exactly what was expected, but now I also know what = common=20 mode voltages it will cope with.
 
Anyway, I have ordered some modern sensors with 0 to 5 V outputs = and I=E2=80=99m=20 going to scale the outputs down to suit the VM1000. I will let you all = know=20 how I get on. If I=E2=80=99m right, then I will have something that = should work with=20 any other monitoring systems that are out there.
 
Yours,
 
Nick
 
*not as easy as it sounds because the sensors are NPT threads and = my=20 system is completely and utterly the way it should be =E2=80=93 = British Standard Pipe=20 thread.
 
 
Sent: Monday, April 21, 2014 4:43 PM
Subject: [LML] Re: VMS1000 pressure gauges on=20 LNC2
 
Nick -
 
The VMS1000 oil and fuel pressures = were designed=20 for the Honeywell MediaMate, which produces 50mV DC full-scale output = when=20 excited with 5VDC. The MediaMate, however, is inferior, antiquated = technology=20 and outrageously overpriced.
A modern, high-quality replacement is = the=20 Measurement Specialties US321. It also produces=20 50mV DC when excited with 5VDC; hence, it's an electrically-DIRECT = replacement=20 for the MediaMate http://www.meas-spe= c.com/downloads/US300.pdf 
A problem, however, is that the = VMS1000's=20 combination of 5VDC excitation and 50mV DC full-scale output is, = apparently,=20 rarely used in industry; hence, I couldn't locate any US321's -in the = needed=20 pressure range- for sale despite an exhaustive search. I contacted = Measurement=20 Specialties last August and learned that they would manufacture them = at a cost=20 of $140 each, with a minimum order of five. So I ordered five @50 psi = (fuel=20 pressure for fuel-injected engines) and five @100 psi (oil pressure). = I=20 ordered them with four foot pigtails to allow direct routing to the = DPU, with=20 no intermediate connector. Attached is a photo of them installed on my = engine.=20 If anyone is interested, I'm offering the extra's for my price of $140 = each.
 
Bill Rumburg
N403WR  (Sonic = bOOm)
Hello Everyone,
 
A few weeks ago we had a discussion about this, and I then went = away=20 and checked my installation. After measuring the voltages I = concluded that=20 the display unit is ok, but both the Oil Pressure and Fuel Pressure = sensors=20 are not behaving.
 
So then I looked into replacements. There was an interesting = post last=20 September from Bill Rumburg about using sensors from Measurement=20 Specialities; the originals are Honeywell Mediamates.
 
Bill was saying the OP and FP transducers are different in = their=20 voltage vs pressure response by a factor of 2 and he was exploring = some=20 alternative devices. But here is another idea. Why not just find a = sensor=20 that gives the correct output for FP? The same sensor will give 2x = the=20 reading if used for OP, but that can be scaled down by 2 with a = simple=20 precision resistor network.
 
If that is correct, and I=E2=80=99ve followed the previous = discussion=20 correctly, then Digi Key have the very item we need:
http://www.digikey.com/product-detail/en/M3421-000006-100PG= /MSP6892-ND/726352
 
What do you think, people?
 
Yours,
 
Nick
 
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