From a hardware engineers standpoint, it would be interesting to see how many people are actually using the different ways of measuring temperature. I’ve got a few requests for adding support for PT100 sensors for instance, but how many people are using those? Is it worth adding support for it?
So the question is: How do you measure the temperature on your 3D-printer? Hot end + bed.
PT100 is a resistance thermometer, btw.
A thermistor is a resistance device as well. You really could combine the first and third options.
Well, yes, but the high resistance of the thermistors most in use, make the circuitry less susceptible to internal heating and thus requires a simpler circuit. I’m assuming the PT100s have external circuitry for handling constant current.
PT100s (RTDs) and TCs both use amps. Thermistors can be read with an ADC and simple voltage divider. Aside from that simplicity factor, thermistors are pretty much inferior. (Inconsistent temp resolution, more variability between units, less usable sensing range, etc.)
My personal opinion is that RTDs are overkill, thermistors are “good enough” for most printers, and thermocouples are a solid middle-of-the-road performer. But it really depends on things like ADC resolution (eg 10bit vs 12bit), whether you want an amp as part of your control board, and so on.
@Mark_Rehorst this is great research, and indeed something I have thought about as well, just never concluded with.
The reason for this poll is actually more to figure out what people want to use, and what people are using, rather than to force a choice on anyone by only offering a single solution in the hardware. Flexibility in hardware usually comes at the cost of a higher BoM, but if only 68% of the people asked here use a thermistor, it’s worth looking into offering other choices as well.
I think all Ultimakers use PT100, maybe excepting some of the oldest original ones. It’s pretty rare to see them used elsewhere but it might be a good choice moving forward for higher end builds because the sensor can handle higher temps than most thermistors. PT100s also seem to be a lot more resistant to RFI & noise than thermocouples.
In terms of firmware support, as far as I’m aware the vast majority of printers (aside from Mightyboards) using PT100s or TCs are using a linear output amp hooked up to an ADC channel, so support is just a linear thermistor table. If you cover that and maybe SPI support for a couple popular SPI amps, you’re done.
@Ryan_Carlyle support would be in the form of disabling the pull-up and/or having a voltage follower to limit input (the max add input is 1.8V)