NTC Thermistor

What it is

A thermistor, a resistor whose resistance falls as it warms, in a divider with a fixed 10 kΩ resistor. At 25 °C the thermistor is 10 kΩ too, so SIGNAL is exactly half of VCC. Warmer, SIGNAL falls; colder, it rises. The front of the board says ANALOG, and the back says RESISTANCE DECREASES AS TEMPERATURE RISES.

Your board reads SIGNAL as a voltage. Turning that into degrees is arithmetic the sketch does itself, in two steps: back to the thermistor's resistance through the divider, then to a temperature through the B equation, using the 10 kΩ and B = 3950 from the thermistor's part number. Neither step is a straight line, which is why map() gets it wrong away from the two points it is given.

VCC is what SIGNAL is a fraction of

On an ESP32 read analogReadMilliVolts on an ADC1 pin. Its ADC reads to about 3.1 V at the default setting, so below about −25 °C the reading stops falling.

Which pin is which

Component side up, header at the bottom, reading left to right:

The back prints TK12 NTC THERMISTOR instead of pin names. Turned over, the square pad is on the right, and it is still GND.

Wiring, in three lines

1. GND to your board's GND.
2. VCC to 5V on an Uno, 3V3 on an ESP32, ESP32-S3 or Pico.
3. SIGNAL to an analog pin: A0 on an Uno, GPIO 34 on an ESP32, GPIO 4 on an ESP32-S3, GP26 on a Pico.

Leave NC unconnected.

Example

#include <math.h>

// Uno: A0. ESP32: 34. ESP32-S3: 4. Pico: 26.
const int SENSOR_PIN = A0;

void setup() {
  Serial.begin(115200);
}

void loop() {
#if defined(ARDUINO_ARCH_ESP32)
  float mv = analogReadMilliVolts(SENSOR_PIN);     // own reference
  float r = 10000.0 * mv / (3300.0 - mv);          // VCC taken as 3.3 V
#else
  float n = analogRead(SENSOR_PIN);                // a fraction of VCC
  float r = 10000.0 * n / (1023.0 - n);
#endif
  float c = 1.0 / (1.0 / 298.15 + log(r / 10000.0) / 3950.0) - 273.15;
  Serial.print(c, 1);
  Serial.println(" C");
  delay(1000);
}

import math, sys, time
from machine import ADC, Pin

# ESP32: 34. ESP32-S3: 4. Pico: 26.
adc = ADC(Pin(4))
ESP = sys.platform == "esp32"
if ESP:
    adc.atten(ADC.ATTN_11DB)                   # to about 3.1 V

while True:
    if ESP:
        ratio = adc.read_uv() / 1000000 / 3.3  # VCC taken as 3.3 V
    else:
        ratio = adc.read_u16() / 65535         # a fraction of VCC
    r = 10000 * ratio / (1 - ratio)
    c = 1 / (1 / 298.15 + math.log(r / 10000) / 3950) - 273.15
    print("%.1f C" % c)
    time.sleep(1)

This short version does not guard against a missing wire. The handbook's sketches do, and average 32 readings for a steadier number.

Where to start

The handbook below is twelve short articles, each with a working figure. The first reading is the wiring and a count; counts to degrees is the arithmetic.

On an ESP32, read reading it on an ESP32 first. And before trusting the second decimal place, how far to trust it.