REFLECTOR: CHT monitor

[Douglas Holub]

It's the minus (-) wire, and it might get tied to ground inside the RMI 
(although that's not the way I'd do it.)

A thermocouple is like a tiny battery whose voltage changes with 
temperature. I've been thinking about it, and if I wanted to measure six 
batteries to see how their voltage changes with temperature, it would be 
fine to tie all their negative terminals together and measure each positive 
terminal individually. I wish I had given it some thought before I wired up 
two double-pole rotary switches for EGT and CHT. It was a pain.

The RMI wiring diagram calls for a double-pole rotary switch, so I'd call 
Ron at RMI first if I were you. I'd be curious to know what you find out.

Doug

----- Original Message ----- 
From: <aminetech at bluefrog.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Wednesday, March 18, 2009 9:54 AM
Subject: Re: REFLECTOR: CHT monitor


> Doug,
>
> As I understand it, one of those leads is considered a ground.  According 
> to RMI's installation manual, the red wire is normally the ground wire.
>
> John
>
> --- douglas.holub at gmail.com wrote:
>
> From: "Douglas Holub" <douglas.holub at gmail.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Subject: Re: REFLECTOR: CHT monitor
> Date: Wed, 18 Mar 2009 08:51:53 -0500
>
> I wouldn't think there would be any ground leads involved with CHT probes.
> The wiring diagram for my RMI CHT probes uses a double pole rotary switch
> that successively sends both CHT leads from each probe to the engine
> monitor.
>
> Doug Holub
> 5 hrs on N2980W, cylinders are cool, oil still hot
> ----- Original Message ----- 
> From: <aminetech at bluefrog.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Tuesday, March 17, 2009 11:59 AM
> Subject: REFLECTOR: CHT monitor
>
>
>> I'm installing a digital CHT, single readout gauge using a Westach switch
>> to switch amoung the 6 cylinders.  The wiring that comes with the switch
>> connects all the grounds into a single lead.  I assume that is not a
>> problem?  Also, the ground wires are larger and I'm wondering why?
>>
>> John
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