Thermistor, thermocouple or PT100? June 15, 2016 10:20AM |
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Re: Thermistor, thermocouple or PT100? June 15, 2016 12:08PM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 15, 2016 01:33PM |
Registered: 8 years ago Posts: 622 |
Re: Thermistor, thermocouple or PT100? June 15, 2016 03:06PM |
Registered: 10 years ago Posts: 14,672 |
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deckingman
Yes could be a bit overkill. From memory of the pics that DC42 posted, I think the daughter boards only have 2 terminals per sensor so probably only support 2 wire PT100s but an accuracy of +/- 1 degree would be plenty good enough for the hot end and bed I'd have thought.
Edit. Just looked again and it looks like there are indeed 4 terminals per sensor, not 2.
Re: Thermistor, thermocouple or PT100? June 15, 2016 03:38PM |
Registered: 10 years ago Posts: 14,672 |
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deckingman
As we will have the choice (with daughter boards) of using thermistors, thermocouples, or PT100 probes what do you experts recommend for a largish printer with potentially longish leads (say 1 to 2 metres)? Accuracy and reliability being more important than low cost. Thanks in advance.
Re: Thermistor, thermocouple or PT100? June 15, 2016 05:55PM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 15, 2016 06:42PM |
Registered: 10 years ago Posts: 14,672 |
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VDX
... any resistive sensor will be much more accurate with 4-wire connection - and any 2-wire type can be used in "4-wire" mode too
It's simply driving the sensor with a constant current and measuring the voltage drop as near at the sensor, as possible - so simply solder 4 wires to the sensor(two at each pin).
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One problem with the PT100 could be the smaller resistive change per centigrade - you'll need a high accurate ADC to get the best from it.
I've used high-speed 24Bit-ADC's for my sensors ...
Re: Thermistor, thermocouple or PT100? June 15, 2016 07:34PM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 15, 2016 11:57PM |
Registered: 8 years ago Posts: 177 |
Re: Thermistor, thermocouple or PT100? June 16, 2016 05:11AM |
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Re: Thermistor, thermocouple or PT100? June 16, 2016 06:32AM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 16, 2016 08:17AM |
Registered: 8 years ago Posts: 622 |
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VDX
... I have some cylindrical PT100 from Heraeus with 2mm diameter but didn't find them at their site.
Here's another 'round' type with 1.8mm diameter - [www.heraeus.com]
Re: Thermistor, thermocouple or PT100? June 16, 2016 08:21AM |
Registered: 10 years ago Posts: 14,672 |
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deckingman
This is for my new (still planned) printer and one of the objectives is to make it as future proof as possible. With that in mind, I've discounted thermistors as I may want to print at elevated temperatures at some point in the future. Thermocouples seem to be potentially problematic with wiring and insulation. Which leaves me with PT100. Initially, the printer will be using a Diamond hot end (although this may change at some point in the future) and the hole for the temperature sensor is 2mm diameter, 10mm deep. I've asked E3d for the dimensions of their probe. I've also found this [uk.rs-online.com] which fits the hole perfectly, has 4 wires and a measuring range of -70 to +500 deg C. which looks to me like it would fit the bill.
Re: Thermistor, thermocouple or PT100? June 16, 2016 09:04AM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 16, 2016 09:06AM |
Registered: 8 years ago Posts: 622 |
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dc42
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deckingman
This is for my new (still planned) printer and one of the objectives is to make it as future proof as possible. With that in mind, I've discounted thermistors as I may want to print at elevated temperatures at some point in the future. Thermocouples seem to be potentially problematic with wiring and insulation. Which leaves me with PT100. Initially, the printer will be using a Diamond hot end (although this may change at some point in the future) and the hole for the temperature sensor is 2mm diameter, 10mm deep. I've asked E3d for the dimensions of their probe. I've also found this [uk.rs-online.com] which fits the hole perfectly, has 4 wires and a measuring range of -70 to +500 deg C. which looks to me like it would fit the bill.
My PT100 sensor from E3D is 3mm diameter and 15mm long. That RS one looks like a good choice too, if 350C max temperature is high enough for you.
Re: Thermistor, thermocouple or PT100? June 16, 2016 09:07AM |
Registered: 8 years ago Posts: 622 |
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VDX
... with two PT100 similar to this RS-types I've done some "max temp" measuring - I've clamped two of the sensors back to back, used one as heater, the other as temp-sensor - got heating and measurind up to +700 degC before stopped ... so should be usable reliable with 500 degC
Re: Thermistor, thermocouple or PT100? June 16, 2016 09:12AM |
Registered: 10 years ago Posts: 14,672 |
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deckingman
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dc42
Quote
deckingman
This is for my new (still planned) printer and one of the objectives is to make it as future proof as possible. With that in mind, I've discounted thermistors as I may want to print at elevated temperatures at some point in the future. Thermocouples seem to be potentially problematic with wiring and insulation. Which leaves me with PT100. Initially, the printer will be using a Diamond hot end (although this may change at some point in the future) and the hole for the temperature sensor is 2mm diameter, 10mm deep. I've asked E3d for the dimensions of their probe. I've also found this [uk.rs-online.com] which fits the hole perfectly, has 4 wires and a measuring range of -70 to +500 deg C. which looks to me like it would fit the bill.
My PT100 sensor from E3D is 3mm diameter and 15mm long. That RS one looks like a good choice too, if 350C max temperature is high enough for you.
Yes, got a reply from E3D confirming those dimensions - too big to fit the Diamond unless I drill the hole out bigger. Ref the RS one, spec says 500C max. Where did you get 350 from? Did I miss something?
Re: Thermistor, thermocouple or PT100? June 16, 2016 09:32AM |
Registered: 8 years ago Posts: 622 |
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dc42
The headline and specification on the product page say 500C, the product details section says 250C, and the datasheet says 350C. Take your pick! I've reported a similar error for the version with 1000mm leads to RS.
Re: Thermistor, thermocouple or PT100? June 18, 2016 05:22AM |
Registered: 8 years ago Posts: 622 |
Re: Thermistor, thermocouple or PT100? June 18, 2016 06:06AM |
Registered: 10 years ago Posts: 14,672 |
Re: Thermistor, thermocouple or PT100? June 18, 2016 06:54AM |
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Re: Thermistor, thermocouple or PT100? June 18, 2016 09:59AM |
Admin Registered: 16 years ago Posts: 13,902 |
Re: Thermistor, thermocouple or PT100? June 18, 2016 10:29AM |
Registered: 10 years ago Posts: 14,672 |
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deckingman
Hi DC,
The thermnal compound is the stuff that RepRap.Me supply with their hot end and looks exactly like this that E3d sell [e3d-online.com] so I'm guessing it ought to be suitable.
The instructions for fitting a thermistor are here.
[reprap.org]
Just wanted to check that one could fit at PT 100 the same way. Would you still recommend not using the thermal paste? Will it still give me an accurate temperature reading?
Thanks
Re: Thermistor, thermocouple or PT100? June 18, 2016 12:36PM |
Registered: 8 years ago Posts: 622 |
Re: Thermistor, thermocouple or PT100? June 29, 2016 02:34AM |
Registered: 8 years ago Posts: 155 |
Re: Thermistor, thermocouple or PT100? June 29, 2016 02:41AM |
Registered: 10 years ago Posts: 14,672 |
Re: Thermistor, thermocouple or PT100? June 29, 2016 03:34AM |
Registered: 8 years ago Posts: 155 |
Re: Thermistor, thermocouple or PT100? June 29, 2016 09:25AM |
Registered: 10 years ago Posts: 14,672 |