Mailing List flyrotary@lancaironline.net Message #6436
From: Bartrim, Todd <sbartrim@mail.canfor.ca>
Subject: RE: [FlyRotary] Re: EMU in the wild
Date: Thu, 11 Mar 2004 12:56:48 -0800
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
RE: [FlyRotary] Re: EMU in the wild

I sure hope they last, because replacing them means going back into that EGT/CHT connector on the EM-2.  I grounded the other 2 EGT inputs, and hooked up 8 foot of CHT wire to each of the CHT's.  These are twisted, and soldered on the ends to make a probe.  These are coiled up in the engine compartment now, for use as experimental temp probes.  Unless I find a specific use for them, they won't be permanently connected to the engine. 

Hi Rusty;
        You mentioned earlier that you were considering a terminal block in the engine compartment, to ease the process of wiring? I take it that you didn't do this?

        The reason that I ask is that I too am planning on this, however there are a few problems with this. I've salvaged from several decommissioned instruments here at work several 32 point terminal blocks attached to a length of cable with 32 -22awg wires. These would be ideal to mount FWF then run the other end back to the 25pin D-sub, however while there should be no issue in using this for the P2 connector it isn't really all that necessary as those points are for fixed sensors that won't be moved. P1 is where it would be really handy, as some of those 8 T/C's will be moved to various locations for various tests and running T/C extension wire back to the EMU will be somewhat of a pain. Unfortunately this poses a problem as by using copper wire from the terminal block to the EMU the cold junction will become the terminal block which will not be at the same temp as the compensated reference junction (EMU). This wouldn't be a huge problem with measuring very high temps such as the EGT, but with lower temps the error would be unacceptable.

        I could still use a terminal block in the engine compartment and just use T/C extension wire from there to the EMU D-sub pins, however extension wire is bulky and stiff so I don't look forward to building and soldering that harness to a D-sub. Possibly a preferable option would be to located the terminal block near the EMU then use copper wire for that section of harness which would be nicer and the cold junction would be at the same temp as the reference junction, but it would still require running T/C extension wire through the firewall, which would be a bit of a pain while experimenting with various T/C locations.

        If you have any suggestions based on your experience with your install I'd like to hear them. Tracy, Ed or anyone else with T/C knowledge, feel free to jump in here. While I understand T/C's, they are not commonly used up here in industry as we've switched to using RTD's which while more expensive, don't require reference junction compensation, so I have limited experience with them, but I'd like to find a way to have a convenient terminal block FWF.

S. Todd Bartrim         (slow day at work, so I'm feeling a little talkative :-)
Turbo 13B
RX-9endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

        "Imagination is more important than knowledge"
                                        -Albert Einstein


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