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Update thermistor_21.h

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reverted back to original code and added additional comment on intended usecase for this probe (5V INA826 supply, 3v3 ADC ref on mainboard)
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Till 2020-09-12 02:27:49 +02:00 • committed by GitHub
parent 5b7c353a22
commit e59d9f073b
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1 changed files with 7 additions and 4 deletions
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Marlin/src/module/thermistor/thermistor_21.h
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@ -23,10 +23,11 @@
#define REVERSE_TEMP_SENSOR_RANGE_21 1
// Pt100 with INA826 amp with 3.3V excitation based on "Pt100 with INA826 amp on Ultimaker v2.0 electronics"
// As the uC ADC reference voltage is 3.3V as well as the INA826 supply/reference, the same table as for 5V excitation is valid.
// The ADC is referring his counts to the reference voltage as the IN826 opamp does scale the output voltage to the supply voltage in the analog domain.
// Note, that the quantization error of this table in conjunction with rounding of the temperature reading can result in a few degrees error most noticeable between datapoints, e.g. 25°C, 35°C, etc.
#undef OV_SCALE
#define OV_SCALE(N) (float((N) * 5) / 3.3f)
// Pt100 with INA826 amplifier board with 5v supply based on "Pt100 with INA826 amp on Ultimaker v2.0 electronics" with 3v3 ADC reference on the mainboard
// If the ADC reference and INA826 board supply voltage are identical, use senosr no. 20 instead.
const temp_entry_t temptable_21[] PROGMEM = {
{ OV( 0), 0 },
{ OV(227), 1 },
@ -73,3 +74,5 @@ const temp_entry_t temptable_21[] PROGMEM = {
{ OV(614), 500 }
};
#undef OV_SCALE
#define OV_SCALE(N) (N)