lml@lancaironline.net Mailing List Archive

Nick -

The VMS1000 obtains oil and fuel pressure by exciting the transducers with 5VDC and they return a 0 - 50 mVDC signal that's linearly proportional to pressure. You almost certainly have the originally-supplied Honeywell Media Mate transducers. Someone here on the LML might have direct knowledge of their internal construction, but I believe they're an older moving-bellows design. If your pressures are otherwise functioning normally, it's difficult to image the problem as anything other than a sticking bellows. While not really a problem -and something you can live with- a modern, high-quality Measurement Specialties transducer is an excellent replacement http://www.meas-spec.com/downloads/US300.pdf

Bill Rumburg

N403WR (Sonic bOOm)

----- Original Message -----

From: Nick Long

To: lml@lancaironline.net

Sent: Friday, March 28, 2014 4:02 PM

Subject: [LML] VMS1000 pressure gauges on LNC2

Hello All,

I’ve got a Lancair 320 and we’ve just re-installed the engine and are in the process of the annual inspection.

Both the fuel and the oil pressure readings on the VMS1000 display are very strange. The fuel pressure gives a reading when there is no pressure and the oil pressure reads very low. A quick check with some old steam gauges suggests the actual pressures are about right. The pressure sensors are both in the engine bay, fed with flexible hoses.

Is this likely to be the pressure sensors? Do they tend to misbehave? Is there an easy way to check them? Or could it be in the wiring or the display unit itself. I can’t see anything in the VMS1000 manual about calibration.

Any help gratefully received.

Thanks,

Nick