Temp Sensor for Thermistor Calibration

I am looking to buy a temperature sensor to check the accuracy of my thermistor and calibrate it if necessary.

Does anyone have a recommendation for a low-cost temperature sensor that is accurate enough for this purpose. (I don't want to spend too much but I also don't want wildly inaccurate readings).

I was thinking about getting a food thermometer and attaching the tip to my hot end with some kapton tape to measure the temperature. I don't need an instant response, but I need to be fairly accurate. This is the one I was looking at Weber Thermometer.

If anyone has used or knows about a low-cost, accurate temperature sensor I'd really appreciate your input.

I was thinking about getting something like this: [www.amazon.com]

That is way better than what I had in mind! So much better that I just ordered one. I'll let you know how well it works once I get a chance to test it out.

Be aware that accurate is a relative term when measuring hotends.
To use a small thermistor successfuly you should have a seperate hole in the heater block and fit it in with some heatsink grease.
I had readings fidder in almost 20 degree C from simply touching the hotend over using heat paste to using a hole for the thermistor.
If in doubt fix the thermistor to bare metal and wrap the hotend with kapton tape.
This way you have more accurate readings as the tape acts like a shield.

I was thinking of making a "landing plate" in the shape of the nozzle with a build in thermistor.
Simply rest the nozzle on the plate and after a few minutes the temp should be stable enough for accurate readings.

The thermocouple will have different readings from the thermistor, if it is mounted at a different place, too ( Surface instead of in-hole)

In real life it doesn´tmatter, if your temp is actually 5°C off from what the LCD says. You have to experiment with each filament, you´ll use anyways.
Good PID tuning and low hysteresis ( thermal grease/ good contact ) is more important, than a "calibrated" temp readout.
-Olaf

Edited 1 time(s). Last edit at 06/23/2015 05:39AM by o_lampe.

With the small probes it should be possible to feed it down the filament guide and get a measurement from inside the hotend. That would at least be an interesting measurement to compare with the printer's readings at different set points.

To get the most accurate temperature I use a small type K thermocouple and a block of culltlefish bone as an insulator. Cut the cuttlefish bone about 20mm to a side by 10 to 15mm thick. Lower your nozzle onto the cuttlefish so that it makes a depression maybe 4 or 5 mm deep, lift the nozzle, position the bead of the thermocouple in the center of the depression and lower the nozzle again. Allow about 5 minutes for the temperature to stabilise. Allowing only instrument errors and maybe a degree of so of tip cooling this should be very accurate.
It is worth extruding a couple om mm of filament immediately after this to make sure no powdered cuttlefish bone is left in the nozzle.

Mike