X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 29 Apr 2014 08:13:32 -0400 Message-ID: X-Original-Return-Path: Received: from vms173007pub.verizon.net ([206.46.173.7] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTP id 6850753 for lml@lancaironline.net; Mon, 28 Apr 2014 21:49:10 -0400 Received-SPF: pass receiver=logan.com; client-ip=206.46.173.7; envelope-from=lancair403@verizon.net Received: from self87aab97f5d ([unknown] [71.176.58.47]) by vms173007.mailsrvcs.net (Sun Java(tm) System Messaging Server 7u2-7.02 32bit (built Apr 16 2009)) with ESMTPA id <0N4R004F8RORAM00@vms173007.mailsrvcs.net> for lml@lancaironline.net; Mon, 28 Apr 2014 20:48:29 -0500 (CDT) X-Original-Message-id: From: "William Rumburg" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: VMS1000 pressure gauges on LNC2 X-Original-Date: Mon, 28 Apr 2014 21:47:56 -0400 MIME-version: 1.0 Content-type: multipart/alternative; boundary="----=_NextPart_000_007C_01CF632B.841843C0" X-Priority: 3 X-MSMail-priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 This is a multi-part message in MIME format. ------=_NextPart_000_007C_01CF632B.841843C0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Nick - The VMS-1000 was a state-of-the-art engine indication/fuel management = system back in the mid-90's and is still quite respectable. However, = it's DPU is comprised of individual electronic devices which are now = obsolete; hence, if any one of them is damaged or fails, you may as well = consider the entire DPU toast. The possiblity of damage to an individual = component is my reason for not experimenting with voltage dividers, etc. = in an attempt to make non-standard sensors work. Fortunately, sensors = are -for the most part- still available. One insurmountable problem, = however, would be replacement of the fuel flow sensor. FloScan went from = an 18K to a 6K unit and fuel flow accuracy requires that sensors "K" = factor be programmed into the DPU, which is no longer possible for the = VMS. The MediaMate's terminals are numbered 1 thru 4 and function as you've = listed; however, terminals 2 and 4 are more correctly identified as - = and + 5 VDC excitaton, with terminals 1 and 3 as + and - mV signal. I've = also failed to mention that the MediaMate's plug-on 'Hirschmann' = terminals are ill-conceived and problem-prone, especially for a mV = signal; whereas, the MSP US 300 series all have a permanent, = factory-installed connection. Bill ----- Original Message -----=20 From: Nick Long=20 To: lml@lancaironline.net=20 Sent: Friday, April 25, 2014 7:55 AM Subject: [LML] Re: VMS1000 pressure gauges on LNC2 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_007C_01CF632B.841843C0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Nick -
 
The VMS-1000 was a state-of-the-art = engine=20 indication/fuel management system back in the mid-90's and is still = quite=20 respectable. However, it's DPU is comprised of individual=20 electronic devices which are now = obsolete;=20 hence, if any one of them is damaged or fails, you may as well = consider the=20 entire DPU toast. The possiblity of damage to an=20 individual component is my reason for = not experimenting with=20 voltage dividers, etc. in an attempt to make non-standard sensors work.=20 Fortunately, sensors are -for the most part- still available. One = insurmountable=20 problem, however, would be replacement of the fuel flow = sensor.=20 FloScan went from an 18K to a 6K unit and fuel flow accuracy requires = that=20 sensors "K" factor be programmed into the DPU, which is no longer = possible=20 for the VMS.
The MediaMate's terminals are = numbered 1 thru=20 4 and function as you've listed; however, terminals 2 and 4 = are more=20 correctly identified as - and + 5 VDC excitaton, with terminals 1 and 3 = as + and=20 - mV signal. I've also failed to mention that the MediaMate's = plug-on=20 'Hirschmann' terminals are ill-conceived and problem-prone,=20 especially for a mV signal; whereas, the MSP US 300 series all have = a=20 permanent, factory-installed connection.
 
Bill
----- Original Message -----
From:=20 Nick Long=20
Sent: Friday, April 25, 2014 = 7:55=20 AM
Subject: [LML] Re: VMS1000 = pressure=20 gauges on LNC2

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=20 mV in 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.=20 The important value is V2-V1. This is what the VM1000 measures and = uses to=20 calculate the pressure.
 
With the device powered up and with no pressure, , then V2 and V2 = should=20 be the same, to within a mV.
This is fairly simple to test, either in the aircraft or on the = bench.=20 You could either use a voltmeter to measure them each accurately, or = put a=20 voltmeter 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=20 where 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=20 PUT A PRESSURE GAUGE ON THE OUTLET OF THE TRANSDUCER AND I HAVE OIL=20 PRESSURE.
THE PROBLEM THEN IS WITH THE TRANSDUCER OR WITH THE = CONNECTION=20 FOR THE DPU. I CAN'T FIND MY TESTING PROCEDURE FOR THE TRANSDUCERS, I = was=20 hoping you could help me 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=20 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" <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=20 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.=20 I quite like the idea of using off the shelf sensors and using the = same one=20 for OP and FP. There is also the background thinking that the VM1000 = is a=20 bit old now and that rather than building a solution around that, I = could=20 devise something with general applicability.
 
Over the holiday weekend I did some more investigation. I built = a rig=20 in my workshop to pressurise the old sensors from my air line = system* and=20 measure the resistance changes and the voltage outputs. The two = sensors gave=20 the right voltage changes (50 mV and 100 mV for 100 psi) but with = horrendous=20 offsets. The zero psi values were way out. So they were working, but = not=20 actually any 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=20 I=E2=80=99m going to scale the outputs down to suit the VM1000. I = will let you all=20 know how I get on. If I=E2=80=99m right, then I will have something = that should work=20 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=20 system is completely and utterly the way it should be =E2=80=93 = British Standard=20 Pipe 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=20 designed for the Honeywell MediaMate, which produces 50mV DC = full-scale=20 output when excited with 5VDC. The MediaMate, however, is inferior,=20 antiquated technology and outrageously overpriced.
A modern, high-quality replacement = is the=20 Measurement Specialties US321. It also=20 produces 50mV DC when excited with 5VDC; hence, it's an = electrically-DIRECT=20 replacement 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=20 Measurement Specialties last August and learned that they would = manufacture=20 them at a cost of $140 each, with a minimum order of five. So I = ordered five=20 @50 psi (fuel pressure for fuel-injected engines) and five @100 psi = (oil=20 pressure). I ordered them with four foot pigtails to allow direct = routing to=20 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=20 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=20 sensors are not behaving.
 
So then I looked into replacements. There was an interesting = post=20 last 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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