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Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

I would seal the sensor with a thin coating of food grade epoxy to protect the device from moisture leakage and use twisted pair or two twisted pair flex wires using 2 as a shield and then use "ferrite CM chokes" to absorb RF interference.

You then need an ADC which is guaranteed accurate to +/- 0.5 bit or perhaps 1 in 256 levels to read 0.5/100% accurate. This is not guaranteed in most Arduino's so you need to use a hardware DAC to test this in Output minus Input on a 2 channel scope and select AC couple for CH1 and CH 2 and then display XY mode CH1 vs Ch2 to get a center dot that traverses a maximum of +/- 1 bit. Any Vref noise in your ADC will cause skipped quantization levels or hysteresis during transitions like 01111 to 10000 and crosstalk from digital ground to input analog ground feed-thru will fail on monotonicity.

Check the TI site for literature on ADC errors.

@Richard Russell << I appreciate the need for 0.5 deg C control in organic cooking styles at low temperatures where living organism begin to die quickly above the Pasteur temperature when the bacteria is killed.

If it were me I would calibrate for 0.1 deg accuracy using my offset gain calibration temperatures between 45 and 65 deg C after it is firmly attached to the well insulated Pot. Then you can out perform any other commercial cooker on the market... assuming it is well insulated in high R value dielectric.

Then for appearance so you can charge $500, wrap it in precision American SS that like the "Spirit of St Louis" is deeply scratched and highly polished. ;)

Personally I would have the SS exterior acid etched by professionals who do this every day with an artwork of historical cooking significance for $50 and then charge extra for custom artwork with personal logo and company name. Just ask if you need a good ref.

Thank you for letting me assist you with your goal.

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

I would seal the sensor with a thin coating of food grade epoxy to protect the device from moisture leakage and use twisted pair or two twisted pair flex wires using 2 as a shield and then use "ferrite CM chokes" to absorb RF interference.

You then need an ADC which is guaranteed accurate to +/- 0.5 bit or perhaps 1 in 256 levels to read 0.5/100% accurate. This is not guaranteed in most Arduino's so you need to use a hardware DAC to test this in Output minus Input on a 2 channel scope and select AC couple for CH1 and CH 2 and then display XY mode CH1 vs Ch2 to get a center dot that traverses a maximum of +/- 1 bit. Any Vref noise in your ADC will cause skipped quantization levels or hysteresis during transitions like 01111 to 10000 and crosstalk from digital ground to input analog ground feed-thru will fail on monotonicity.

Check the TI site for literature on ADC errors.

Thank you for letting me assist you with your goal.

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

I would seal the sensor with a thin coating of food grade epoxy to protect the device from moisture leakage and use twisted pair or two twisted pair flex wires using 2 as a shield and then use "ferrite CM chokes" to absorb RF interference.

You then need an ADC which is guaranteed accurate to +/- 0.5 bit or perhaps 1 in 256 levels to read 0.5/100% accurate. This is not guaranteed in most Arduino's so you need to use a hardware DAC to test this in Output minus Input on a 2 channel scope and select AC couple for CH1 and CH 2 and then display XY mode CH1 vs Ch2 to get a center dot that traverses a maximum of +/- 1 bit. Any Vref noise in your ADC will cause skipped quantization levels or hysteresis during transitions like 01111 to 10000 and crosstalk from digital ground to input analog ground feed-thru will fail on monotonicity.

Check the TI site for literature on ADC errors.

@Richard Russell << I appreciate the need for 0.5 deg C control in organic cooking styles at low temperatures where living organism begin to die quickly above the Pasteur temperature when the bacteria is killed.

If it were me I would calibrate for 0.1 deg accuracy using my offset gain calibration temperatures between 45 and 65 deg C after it is firmly attached to the well insulated Pot. Then you can out perform any other commercial cooker on the market... assuming it is well insulated in high R value dielectric.

Then for appearance so you can charge $500, wrap it in precision American SS that like the "Spirit of St Louis" is deeply scratched and highly polished. ;)

Personally I would have the SS exterior acid etched by professionals who do this every day with an artwork of historical cooking significance for $50 and then charge extra for custom artwork with personal logo and company name. Just ask if you need a good ref.

Thank you for letting me assist you with your goal.

2 added 894 characters in body
source | link

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

I would seal the sensor with a thin coating of food grade epoxy to protect the device from moisture leakage and use twisted pair or two twisted pair flex wires using 2 as a shield and then use "ferrite CM chokes" to absorb RF interference.

You then need an ADC which is guaranteed accurate to +/- 0.5 bit or perhaps 1 in 256 levels to read 0.5/100% accurate. This is not guaranteed in most Arduino's so you need to use a hardware DAC to test this in Output minus Input on a 2 channel scope and select AC couple for CH1 and CH 2 and then display XY mode CH1 vs Ch2 to get a center dot that traverses a maximum of +/- 1 bit. Any Vref noise in your ADC will cause skipped quantization levels or hysteresis during transitions like 01111 to 10000 and crosstalk from digital ground to input analog ground feed-thru will fail on monotonicity.

Check the TI site for literature on ADC errors.

Thank you for letting me assist you with your goal.

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

Thank you for letting me assist you with your goal.

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

I would seal the sensor with a thin coating of food grade epoxy to protect the device from moisture leakage and use twisted pair or two twisted pair flex wires using 2 as a shield and then use "ferrite CM chokes" to absorb RF interference.

You then need an ADC which is guaranteed accurate to +/- 0.5 bit or perhaps 1 in 256 levels to read 0.5/100% accurate. This is not guaranteed in most Arduino's so you need to use a hardware DAC to test this in Output minus Input on a 2 channel scope and select AC couple for CH1 and CH 2 and then display XY mode CH1 vs Ch2 to get a center dot that traverses a maximum of +/- 1 bit. Any Vref noise in your ADC will cause skipped quantization levels or hysteresis during transitions like 01111 to 10000 and crosstalk from digital ground to input analog ground feed-thru will fail on monotonicity.

Check the TI site for literature on ADC errors.

Thank you for letting me assist you with your goal.

1
source | link

Using the LM335Z, you can calibrate the offset and gain error for any given sensor with 2 test readings at 0'C 100'C with ice and boiling water.

Then get a verification reading at mid range say 50'C.

You can make a test jig and calibrate one sensor as your silver standar against another the gold standard thermometer. You then save the errors expected-actual and calculate a linear progression or gain and offset number to save in EEPROM so they become a calibrated set. If you get a batch, you may find they all have the same offset and gain error which you can correct in software to display the corrected reading.

With 0.1'C standards you can expect 0.2'deg error and use any display you choose to guarantee that 0.5'C error for your critical setpoints.

See Fig 3

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000459.pdf

Thank you for letting me assist you with your goal.