From: "Charlie England ceengland7@gmail.com" <flyrotary@lancaironline.net>
Received-SPF: pass
 receiver=logan.com; client-ip=209.85.161.44; envelope-from=ceengland7@gmail.com
Subject: Re: [FlyRotary] Re: Temperature sensors
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
References: <list-14603@logan.com>
Message-ID: <cc69dd1b-cc26-e83b-556f-69218140a672@gmail.com>
Date: Fri, 21 May 2021 20:47:31 -0500
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.10.2
MIME-Version: 1.0
In-Reply-To: <list-14603@logan.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US

That should make it fairly simple to roll your own; you can silver 
solder the junction into the fitting after you weld the junction.

On 5/21/2021 8:27 PM, Finn Lassen finn.lassen@verizon.net wrote:
> The EM3 likes grounded thermocouple wires, however not really sure 
> it's required.
> They go into balanced inputs. Actually there are four 8x1 multiplexers 
> in the EM3. They have clamping diodes to protect inputs.
>
> Finn
>
> On 5/21/2021 4:36 PM, Charlie England ceengland7@gmail.com wrote:
>> Don't forget to check on whether the EM3 wants grounded or ungrounded 
>> probes. I forget which is which, but one type of 'meter' will accept 
>> either style; the other won't.
>>
>> On 5/21/2021 2:43 PM, Finn Lassen finn.lassen@verizon.net wrote:
>>> When I made my own engine monitor for my RV-3 back in 1999 I found 
>>> it easiest to use sensors that output linear 0 to 5V.
>>>
>>> So when I got an EM3 from Tracy, I modified it to use such sensors 
>>> (LM35, TMP35, TC03 and similar ICs). My reasoning was that they were 
>>> spec'd to accuracy of a couple of degrees over temperature range of 
>>> interest.
>>>
>>> I wondered why the EM3 had 8 EGT and 8 CHT inputs. (Actually in the 
>>> EM3 the 8 CHT inputs also go into the same MAX6675 chip designed for 
>>> Type K thermocouple (EGT) wire.)
>>>
>>> After several failures and weird readings of LM35's I'm now 
>>> beginning to see the wisdom of Tracy's approach. And the LM35CAZ is 
>>> not cheap either.
>>>
>>> If you buy a roll of type K thermocouple wire (less than $1/foot), 
>>> even if it's off a bit compared to an ideal Type K wire,  all 
>>> measurement points should be accurate relative to each other. And 
>>> you just need to calibrate one input for absolute accuracy and use 
>>> those calibration factors for all the other inputs.
>>>
>>> I've spent a lot of time trying to figure out why the coolant output 
>>> from my right radiator is so much lower than the left's. I even made 
>>> 3/4" cu tubing inserts with 1/4" wells in them for the ICs to make 
>>> sure I was measuring actual fluid temps.
>>>
>>> After swapping the hoses to the radiators,  the coolant out (out 
>>> from engine) sensor now inexplicably reads lower by more than 20 deg 
>>> F  than the in-engine sensor. Thought it might have been air in 
>>> coolant near sensor, but lower readings remain after multiple engine 
>>> runs,
>>>
>>> For the CHT inputs, I had bought Type J thermocouple wire, reasoning 
>>> that it'd be more sensitive than Type K. Well, 50uV/C is really not 
>>> much better than 41uV/C, and being fed into a chip that expects Type 
>>> K really makes it much harder to re-correct (the MAX6675 chip 
>>> corrects for ambient temp for Type K not J).
>>>
>>> So, I think I'll rip out all sensors, order a roll of Type J wire, 
>>> make and install new sensors: 1/8NPT plugs drilled for 5/32" brass 
>>> tubing with wire twisted and soldered to the pinched-shut brass 
>>> tubing. (My old sensors were 1/8NPT plugs drilled for 1/4" cu tubing 
>>> that the LM35's could fit in.)
>>>
>>> Quite a bit of work, but hopefully will pay off in terms of reliable 
>>> temperature readings. Without those I don't think I can optimize the 
>>> cooling system.
>>>
>>> Hope that others may learn from my mistakes.
>>>
>>> Finn
>>>
>>>
>>> ---
>>> This email has been checked for viruses by Avast antivirus software.
>>> https://www.avast.com/antivirus
>>>
>>>
>>> -- 
>>> Homepage:  http://www.flyrotary.com/
>>> Archive and UnSub: 
>>> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>>
>>
>
>
> -- 
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub: 
> http://mail.lancaironline.net:81/lists/flyrotary/List.html


-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus