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Revision to Connecting thermistors or PT1000 temperature sensors

Tony

== Connecting ==
 
Connect the bed temperature thermistor or PT1000 sensor to the BED_TEMP connector. Connect your first extruder thermistor or PT1000 sensor to the E0_TEMP connector. If you have a second hot end, connect its thermistor to E1_TEMP.

You can connect PT1000 temperature sensors to the thermistor connectors instead of thermistors.
Connect the bed temperature thermistor or PT1000 sensor to the BED_TEMP connector. Connect your first extruder thermistor or PT1000 sensor to the E0_TEMP connector. If you have a second hot end, connect its thermistor to E1_TEMP.

You can connect PT1000 temperature sensors to the thermistor connectors instead of thermistors.
 
== Configuring the firmware ==
For the technically minded: firmware 1.17 and later uses the Steinhart-Hart thermistor model. The M305 C parameter is the Steinhart-Hart '''c''' parameter, the M305 B parameter is the reciprocal of the Steinhart-Hart '''b''' parameter, and the Steinhart-Hart '''a''' parameter is calculated from the resistance at 25C. If you don't provide a C parameter, then C defaults to zero and the Steinhart-Hart equation reduces to the beta-value equation.
 
'''Warning''': Some thermistors meant for high-temperature work (for example those provided with the Dyze hot end) may have such a high resistance at room temperature that they read as open. This will generally cause heater faults as soon as you start heating. There has been discussion of a number of workarounds; a search of the forum may yield some good suggestions. For really satisfactory results you may need to switch to a thermocouple or PT100thermocouple,PT100 or PT1000 sensor.
'''Warning''': Some thermistors meant for high-temperature work (for example those provided with the Dyze hot end) may have such a high resistance at room temperature that they read as open. This will generally cause heater faults as soon as you start heating. There has been discussion of a number of workarounds; a search of the forum may yield some good suggestions. For really satisfactory results you may need to switch to a thermocouple or PT100thermocouple,PT100 or PT1000 sensor.
 
=== PT1000 sensors ===
[code]M305 P1 X501 R4700 ; heater 1 uses a PT1000 connected to thermistor channel 1 which has a 4.7K series resistor[/code]
 
PT1000Note: '''PT1000 sensors connected to thermistor inputs will generally be less accurate and have lower resolution than PT100 sensors connected via the RTD daughter boardboard''', especially when used with the SAM3X8E-based Duets (0.6/0.8.5).
PT1000Note: '''PT1000 sensors connected to thermistor inputs will generally be less accurate and have lower resolution than PT100 sensors connected via the RTD daughter boardboard''', especially when used with the SAM3X8E-based Duets (0.6/0.8.5).
 
=== Note for users of Duet 0.6 boards and DueX4 boards ===
 
* With the machine cold, see what temperatures the are displayed for the bed and hot end(s), and compare that with room temperature.
* AddIf using thermistors, add H parameters in the M305 commands to get readings close to room temperature. If the readings are too low, use a positive H parameter to bring the readings up to the correct value. If the readings are too high, use a negative H parameter. All heater numbers should need the same value of H parameter - any residual differences you see are probably caused by thermistor tolerances. You should never need to use an H parameter below -100 or above 100, and it is rare to need a value outside the range -30 to 30.
* AddIf using thermistors, add H parameters in the M305 commands to get readings close to room temperature. If the readings are too low, use a positive H parameter to bring the readings up to the correct value. If the readings are too high, use a negative H parameter. All heater numbers should need the same value of H parameter - any residual differences you see are probably caused by thermistor tolerances. You should never need to use an H parameter below -100 or above 100, and it is rare to need a value outside the range -30 to 30.
* If you use a PT1000 instead of a thermistor, then the L parameter mostly affects the reading at low temperatures (the opposite to when using a thermistor), so you may wish to adjust it to get the correct room temperature reading, or to get a 0C reading when you substitute a 1K resistor for the PT1000.
* '''Very important!''' Check that if you disconnect the thermistors, the temperature in the web interface reads as '''error'''. If instead it reads a very low temperature, reduce the H parameters until it does report '''error''', then reduce them a bit more.

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