Thermistor r2.5


 

James P

New member
Just finished assembling my first board, but have a part left over (thermistor r2.5) for ambient temperature reporting. Where does it go?
 

RalphTrimble

TVWBB Diamond Member
Just finished assembling my first board, but have a part left over (thermistor r2.5) for ambient temperature reporting. Where does it go?

This optional part would go from the switched leg of the last food probe to ground to function as an ambient temperature reference. In reality the LCD and other heat from the HM generally make the ambient temp reading of a boardf mounted thermistor a bit higher than reality... totally optional....

...and btw, when you enable the ambient temp thermistor you set the scale displayed by the HM to be from the ambient temp to the pit/food temp, meaning a fairly large range. If you disable ambient temp readings your HM will show you a much smaller and more accurate scale that is focused around the target pit and food temps....
 

Bryan Mayland

TVWBB Hall of Fame
You can see a thermistor here on the top right soldered to the correct pins. You can point it out to right and drill a hole to make it come out of the case but I found the difference to be modest. It's never quite right and way off if the HeaterMeter is in the sun.
 

Bob Ivey

TVWBB Emerald Member
So Bryan, Are you saying that it would be better to not use an ambient temperature thermistor? Given Ralph's comment, it would seem so.
Bob

Edit: I noticed when I had my HM on my desk to update the firmware that the ambient temp showing on the HM was 4 or 5 degrees higher than the thermometer in my office.
 
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RalphTrimble

TVWBB Diamond Member
I'm not saying don't use it, cause you can always disable it in the software even if you have it installed... but it is completely optional and usually not quite accurate if installed on the board around the heat from the HM... Someone came up with the idea of putting the thermistor on a probe jack so when you plug it in it is outside the HM case in open air, that seems like it would be pretty accurate...
 

Bob Ivey

TVWBB Emerald Member
Ralph, the first question is why are you up so late. My excuse is I just don't sleep well. Mild sleep apnea and a touch of insomnia I guess.

As for putting the thermistor on an external jack, that is you I have mine and what I find is that if my HM is near the smoker, the ambient temp shows considerably hotter than the surrounding air. The real question I think is how does the ambient temp in the HM affect the performance of the HM and the cook?
 

RalphTrimble

TVWBB Diamond Member
Well, the ambient temp thermistor will have no direct effect on the cook, but having it on will put a line on the graph way down low and make the scale of the graph be larger (from room temp to a bit above the setpoint). If you are using a food probe in a meat you are going to have that range anyways, but if you are cooking say ribs or steak and have no probes in food, and don't have your ambient temp thermistor enabled, then your HM graph will display a much more narrow temp range centered around the setpoint instead of extending all the way down to room temp..... but like I said, you can disable the ambient temp probe in software if you like so it's not an issue. In the beginning I always had an ambient temp reading on the screen, then when I started to microscope the performance of the probes and TC and CAT5 cable etc I started to disable the ambient temp. When I had the ambient temp enabled and thermistor installed inside the HM case it always read quite a bit higher than the actual ambient temp, so I've kinda quit using them these days....
 
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Richard Apgood

New member
i missed the optional parts. i am purchasing the thermistor. my question is does it mater which leg goes where and what is the green wire in the picture on post #3?
 

RalphTrimble

TVWBB Diamond Member
Nope, just across the ground and switched leg on the probe jack is all you need to worry about, doesn't matter which leg of the thermistor you put where...
 

 

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