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Date: Fri, 18 May 2007 13:31:20 -0400 (EDT)
Subject: Re: [FlyRotary] EC2 probe grounding.
From: jewen@comporium.net
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Dave,
I am not flying, but the following is considered practical.  A thermistor
does not have a linear output per temperature.  The curve is is a 3rd
order equation (typically Steinhart-Hart equation) which the receiving
device has to interpret.  What that means is if you use a thermistor that
does not match any one of the 3 thermistor constants, the EC2 program will
not accurately convert the electrical signal to temperature.  To avoid
data errors and problems, I would encourage you to use the thermistor that
was supplied with the EC2.

Joe


On Fri, May 18, 2007 1:06 am, David Staten wrote:
> Just pinging the group on this.
>
>
> Chris (and every once in a while I) are to the stage of wiring up
> goodies to the EC2. We have the injectors, resistors and most of that stuff
> done. Next is the inlet air temp sensor for the EC2 (to be followed by all
> the other sensors for the EM2).
>
> There are two wires for the EC2 air temp sensor. There are conflicting
> instructions and diagrams with regards to a new and old scheme that involve
> 2 of 3 possible pins on the plug (I think it was 1, 11 and 31,
> but not positive - you can look at the EC2 diagrams regarding this.
>
> Anyways, the VDO air temp probe I am using is a 1/8" NPT 300 degree F
> with a terminal on top that can receive a female spade connector.
>
> The top terminal is clearly insulated from the rest of the probe, and
> the body of the probe is the ground.
>
> What is the best method for wiring this type of probe.. obviously one
> wire to the top terminal, the positive if so designated. But do we put a
> ring terminal on the body of the probe and hook up the second EC2 wire to
> it? Or do we consider the engine block the ground, which the intake will
> be firmly attached to, and connect the second wire to our forest of tabs
> grounding block on the firewall.
>
> It seems that grounding the probe with a ring terminal can introduce a
> ground loop because now there are two potential paths back to the EC2. Are
> the air temp leads electrically isolated (transformer coupled, for
> instance) or is a ground loop possible.
>
> More than anything else, I would like to hear from those of you who are
> flying with the EC2, because at this point I need practical, not
> theoretical help. I know Tracy is off the grid, so I may wait a while to
> hear from him, but the rest of you with EC2 rotary time, please tell me
> how your set-up is set up.
>
> Dave (and Chris)
>
>
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