Hot end temperature accuracy when cold: please post your measurements

Hi all,

In my latest firmware (057r-dc42) I have increased the ADC resolution to 12 bits, which gives a hotend temperature resolution of about 0.7C. Since then I have further increased the resolution by using 1-bit oversampling.

I would now like to address the accuracy of the reading, by adding the C term from the Steinhart-Hart thermistor equation. Mine reads several degrees low, and from other posts I have seen in this forum, I think this is true for many of you. So I would like as many of you as possible to post your readings, so that I can program in a average value for the C term. I shall adjust the beta term at the same time so as to keep the temperature readings at about 200C consistent with the present readings, unless someone provides me with good evidence that the present readings are inaccurate.

Therefore, if you are running 057r-dc42 software or are prepared to install it (go to [github.com] and press Raw), please can you do the following.

When the Ormerod has not done a recent print (so that the bed and extruder are both at room temperature), and does not have bright sunlight falling in it:

1. Position the print head over the centre of the bed.
2. Allow the print head temperature to stabilise.
3. Record the bed temperature reported by the Duet, extruder temperature reported by the Duet, and (if you have a good thermometer), the air temperature in the vicinity of the print head.
4. Post your readings in a reply to this thread.

Thanks - David

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hello David,
thanks for your update, I've just flashed it on my Duet. I have not printed anything today, so both the print head and the heated bed should be at the same temperature.
Here are my readings:

Bed temperature: 21.9 °C
Extruder temperature: 11.8 - 12.7 °C, slightly varying between those values.

I have an infrared thermometer and it reports 22.5 °C at the heated bed and 23.2 °C at the print head.

I just happen to have a PT1000 RTD taped to the centre of the bed as I was testing a new insulator last night. The bed heater has been off for hours so everything should have equalised.

PT1000 - 16.4
Bed thermistor - 16.7
Extruder - 6.7/7.8

For completeness, a thermocouple probe in free air is 16.3.

14:32 UK beautiful day
room 20.0
Ormerod 187; (Alpine PS 15.7V - 5V. by USB hub)
Bed: 18.4 Extruder 2.4
;(PSU 300W 13.1V - 5V. by Duet Board)
Bed 20.6 Extruder 21.2
This is the old "q" version
I would point out later with the new "r" firmware

16:35
firmware "r" ...(busy day)
room 20.6
Ormerod 187;
Bed: 19.9 Extruder 6.7
Ormerod 187 Bamboo
Bed 22.0 Extruder 25.5


Dario

Edited 1 time(s). Last edit at 03/03/2014 10:49AM by Ormerod187.

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Ormerod 187
Firmware Electronics: Duet 0.6
Firmware Version:1.18.1 (2017-04-07)
Web Interface Version:1.15a
Slic3r 1.2.9a and Simplify3D 4.0.0
[www.dropbox.com]

Thanks to those of you who have responded so far. Here are my figures:

Head 18.0/18.4
Bed 23.0/23.1
Thermometer 20

From the reports so far, it appears to me that the extruder thermistor reads consistently below the bed thermistor, except in Ormerod187's bamboo build. Ormerod187, are you sure you used exactly the same hot end thermistor as supplied with the Ormerod, which is a 1% tolerance thermistor sourced from Digikey I believe?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

looks same... but I'm not sure about these kinds of things...
the bed thermistor from RepRap
the hot end thermistor same....
I do not know...
I have another one but I should try ...


Dario
p.s. I will check visually the best temp. for printing

Edited 1 time(s). Last edit at 03/03/2014 10:53AM by Ormerod187.

---

Ormerod 187
Firmware Electronics: Duet 0.6
Firmware Version:1.18.1 (2017-04-07)
Web Interface Version:1.15a
Slic3r 1.2.9a and Simplify3D 4.0.0
[www.dropbox.com]

Ormorod unused for 24hr+
Ambient on table 19 (IR non-contact thermometer)
Head 18.9/19.6
Bed 20.3/20.4

---

RS Components Reprap Ormerod No. 481

Have not printed today so room temperature

Quote

2. Allow the print head temperature to stabilise.

Placed a thermometer in line with a fan at to normalize the temperature bed, hotend and thermometer for half an hour

Quote

3. Record the bed temperature reported by the Duet, extruder temperature reported by the Duet, and (if you have a good thermometer), the air temperature in the vicinity of the print head.

waited 10 minutes to let the air settle and made 10 measurement, here the average of those:

T: 20,51
B: 19.95
Room temp: 19.8

T fluctuation 0.7
B fluctuation 0.1 (no heat spreader, 4mm glass)

Edit: M115: FIRMWARE_NAME:RepRapFirmware FIRMWARE_VERSION:0.57r-dc42 ELECTRONICSuet DATE:2014-03-02

Erik

Edited 1 time(s). Last edit at 03/03/2014 12:35PM by ormerod168.

Readings taken between 19:35 - 19:50

Ambient Air Temp : 20.5 to 21.0
Bed Temp : 21.2 to 21.7
Head Temp : -3.3 to -5.3 (113.4k ohms to 113.8k ohms)

My hot end temp has always been a bit dodgy, so I've included the a resistance readings too, taken at the 6 way loom connector.


Matt

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Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

My printer's been offline today (doing some rebuilding), but I tend to get similar readings to Matt on older firmware, haven't tried the new yet (I tabulated mine somewhere on the forum a while ago) - I actually have to turn the heating on in the room (or heat up the bed and put the nozzle near it) to get the firmware to view my hotend as not being disconnected on chilly mornings - I'll be fitting a different thermistor soon to avoid this

Ray

I'm wondering what the tolerance on the 1k thermistor series resistors fitted on the Duet board is - they could be part of the problem. I'll add a couple of 1k 0.1% resistors to my next component order.

Edited 1 time(s). Last edit at 03/03/2014 03:35PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Recently I've been running on the duet from T3P3D, I'll be swapping back to the RRP one tomorrow - I'll feed back what variation in readout there is between this sample of two,

Ray

Head reading 31.9
Bed reading 26.4

Infa red Thermometer reading 25.8

Hope this helps

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Andy Hare

Is it not possible to add some calibration option so that by writing some variables in cold store per printer ( Either eeprom if there is any or on the ini file on the SDcard) the raw readings from the atod are converted into actual temperature values and these are the values reported to the user?

EDIT: Will try to get hold of a thermometer today and give some samples

regards
Andy

Edited 1 time(s). Last edit at 03/04/2014 03:40AM by kwikius.

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

No thermometer yet but reckon actual room temperature is around 15 deg c.

Firmware version :0.57r-dc42

Readings

T:11.8 B:19.9
T:11.8 B:20.0
T:9.9 B:20.0
T:9.9 B:20.1
T:11.8 B:20.1
T:11.8 B:20.0
T:11.8 B:20.1
T:10.9 B:20.1
T:11.8 B:20.1

regards
Andy

---

Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Room temperature 22 degrees, Ormerod has had 15 hours unpowered to reach thermal equilibrium.
Hotend temp jumps a lot more than bed temp - mostly between 23 and 25 but with occasional excursions to 18.5 and 26.5
Bed temp continuously fluctuates in a narrower range between 23.3 and 23.7

Firmware 0.57q-dc42 (2014-02-24)

Dave
(#106)

Hi dc42,

My readings:
Hot end Bed
8.9 21.9
7.8 21.9
8.9 21.9
7.8 21.9
8.9 21.9
7.8 21.9
8.9 21.8
7.8 21.9
9.9 21.9
6.7 21.8
8.9 21.8
room temp around 21.

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appjaws - Core XYUV Duet Ethernet Duex5
firmware 3.1.1 Web Interface 3.1.1
Ormerod 1-converted to laser engraver, Duet wifi
OpenSCAD version 2020.07
slic3r-1.3.0, Simplify3D 4.1.2, Cura-4.4.1

Hi dc42,

My printer was unpowered from Yesterday.
Hotend temperature is almost stable at 21.2°C but there are occasional excursions (one single read every 8..15secs) to 18.6°C and 23.5°C (every 8..20secs).
Bed temperature fluctuates in a range from 21.5°C to 21.22°C (about every 2 reads)
Temperature room 20.6°C
Firmware 0.57q-dc42

Roberto

Edited 1 time(s). Last edit at 03/04/2014 11:23AM by gammasistemi.

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RS Ormerod #117

Quote
dc42
I'm wondering what the tolerance on the 1k thermistor series resistors fitted on the Duet board is - they could be part of the problem. I'll add a couple of 1k 0.1% resistors to my next component order.

I think this is a good call dc - I connected up my replacement RRP duet today and it reads around 18°C at an ambient of 20 - I'll tabulate both if I get a chance tomorrow, but the T3P3 (and the original RRP) duet both gave close to zero (or slightly negative) at 18 from memory - presumably because of variation in the series resistor (I've still got the original wiring harness between the duet and the hotend). [NOTE this is with 57Q, not R, I'll do baseline 57Q readings on both then 57R for comparison tomorrow]

Ray

Edited 1 time(s). Last edit at 03/04/2014 11:40AM by rayhicks.

18:01:55 T:15.6 B:17.4
18:01:52 T:15.6 B:17.4
18:01:49 T:15.6 B:17.4
18:01:46 T:15.6 B:17.4
18:01:43 T:15.6 B:17.0
18:01:40 T:18.6 B:17.4
18:01:37 T:15.6 B:17.4
18:01:34 T:15.6 B:17.4
18:01:30 T:15.6 B:17.4
18:01:22 T:15.6 B:17.4

what is the 18.6 doing in there?
Ambient 16.6 (cheap digital thermometer so no clue how accurate)

Ormerod sat idle for a day, so should be stable.

T min 21.5 mean 22.1 max 22.1
B min 22.1 mean 22.2 max 22.3
Bed temp 21.9 measured by K type thermocouple taped to the glass, using Fluke 189 DMM

FIRMWARE_NAME:RepRapFirmware FIRMWARE_VERSION:0.57r-dc42 ELECTRONICSuet DATE:2014-03-02

Dave

Edited 1 time(s). Last edit at 03/04/2014 04:34PM by epninety.

Hi,

I realized the thermitor top thermisor is disconnected.. But when I send M105 from Arduino serial monitor I receive: T:44.5 B:22.0 ...
How can be possible?

Thanks

A disconnected thermistor should read -273C. So you have a board or wiring fault somewhere. What reading do you get if you disconnect the thermistor connections where they plug in to the Duet board?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].