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How to measure heater block temperature?

Posted by dlc60 
How to measure heater block temperature?
August 08, 2017 02:41PM
Hi all,

I'd like to confirm the temperature settings on my printer. I have a non-contact IR "gun" that measures the bed just fine (and it is quite close to what the code thinks). However, it can't seem to measure or focus on the heater block.

What does everyone else use to confirm temperature values?

Thanks,
DLC
Re: How to measure heater block temperature?
August 08, 2017 03:15PM
IR guns cannot measure reflective surfaces, such as aluminum.

Get a Thermocouple probe and meter from china eg (https://www.aliexpress.com/store/product/tm-902c-temperature-meter-tm902c-digital-Thermometer-Thermocouple-Probe-Thermocouple-Needle-Probe/1200599_32301853895.html)
Just the first google showed me.. not a preference or recommendation
Re: How to measure heater block temperature?
August 08, 2017 04:52PM
You can buy multimeters with thermocouple probes from China... quite cheap.
Re: How to measure heater block temperature?
August 08, 2017 05:00PM
I have a Vellman with a K-type thermocouple. I'll tape the probe to the heat block and see what it says. These often do not move very quickly because of their thermal mass on that long stem.

I wonder if smearing some black PLA on the heat block will allow the IR thermometer to work.
Re: How to measure heater block temperature?
August 09, 2017 07:23AM
I am not having much luck with the DVM and thermocouple checking. If I trust what I have my heads never get over 170C.
It also takes a long time to reach a stable temperature. Is this what everyone sees with these?

DLC
Re: How to measure heater block temperature?
August 09, 2017 08:16AM
I had the same problem, the hotend temperature was not in sync with the recommended temperature for the PLA.

You can measure the temperature from aluminum with a IR gun, but you have to adapt the emission factor to the material. The range for aluminum is quite large, it depends on the surface.In addition the measuring spot on my IR thermometer is several cm² and measuring reliable such a small object like a hotend is not possible.
It has a K-Type Thermocouple in addition, but the probe is pipe which is appr. 3mm thick. Great to measure fluids, not so great to measure hotends.

I got myself a thermocouple amplifier from Adafriut and a Type K Thermocouple with a small head of the probe. You can add the small probe under the screw which holds the NTC of the hotend.
The amplifier connects to an Arduino and here is detailed description how to do it.

You get the amplifier and probe also cheaper from China, but I deliberately went for the more expensive one hopping they are using an original MAX31856

With the thermocouple I created a new NTC table for the Marlin and now the recommendations for the PAL are in sync with the hotend temperature. At high temperatures it was almost 20°C off

Peter
Re: How to measure heater block temperature?
August 09, 2017 11:46AM
I purchased a ADM02 DVM, Did not need an expensive DVM already have a Fluke just need to verify temperatures. Thou now I use it more than the Fluke as it has a lighted screen.
And auto-ranging features. Cost me $12 and change, used it on my 3D Printer had almost exactly the same temperature readings.
Re: How to measure heater block temperature?
August 09, 2017 12:55PM
Quote
PeterHi
I had the same problem, the hotend temperature was not in sync with the recommended temperature for the PLA.

You can measure the temperature from aluminum with a IR gun, but you have to adapt the emission factor to the material. The range for aluminum is quite large, it depends on the surface.In addition the measuring spot on my IR thermometer is several cm² and measuring reliable such a small object like a hotend is not possible.
It has a K-Type Thermocouple in addition, but the probe is pipe which is appr. 3mm thick. Great to measure fluids, not so great to measure hotends.

I got myself a thermocouple amplifier from Adafriut and a Type K Thermocouple with a small head of the probe. You can add the small probe under the screw which holds the NTC of the hotend.
The amplifier connects to an Arduino and here is detailed description how to do it.

You get the amplifier and probe also cheaper from China, but I deliberately went for the more expensive one hopping they are using an original MAX31856

With the thermocouple I created a new NTC table for the Marlin and now the recommendations for the PAL are in sync with the hotend temperature. At high temperatures it was almost 20°C off

Peter

This is a great idea. I have used other Adafruit stuff - I will build mine onto a "Feather Basic" with a cheap display. This will be a cool setup because they have Thingaverse thing STL files to make enclosures - And this looks like a good project for it!

K-type thermocouples can be off by 3-6 deg, so they are not perfect, but they are close enough. I checked mine and got 0C in an ice bath and 91C in boiling water. Since I live at 1526 meters, water boils at 94.5C, so 3 degrees off is pretty close. Now I _know_ that my DVM temperature sensor is pretty close. However a 20cm long metal probe is not an ideal temperature sensor for this task, hence the Adafruit solution.

My Velleman DVM was pretty cheap, and I've had it for over 10 years, we will see what I can make work and what is actually going on...

Thanks all,
DLC
Re: How to measure heater block temperature?
August 09, 2017 05:04PM
Try taking the nozzle out and putting your DVM probe inside the hotend. That should give you a consistent temperature pretty close to what the thermocouple sees.
Re: How to measure heater block temperature?
August 09, 2017 05:10PM
Quote
frankvdh
Try taking the nozzle out and putting your DVM probe inside the hotend. That should give you a consistent temperature pretty close to what the thermocouple sees.

That is a really good idea.

DLC
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