This is an NXP KTY81/110 PTC thermistor connected to a 3-meter cable, 2 × 0.5 mm². It changes resistance positively as the temperature increases. It's a nice, inexpensive solution when you need to detect fairly low or high temperatures and don't need something super precise. It operates from -67 to +302 °F (-55 to +150 °C).

Run this from your microcontroller system to check remote temperatures where your main system can't handle the temperatures, or where there simply isn't room for your whole system in the test area (or access to the system would be problematic).

If the area to be tested is closer or farther away than three meters, you can get a 1-meter or a 5-meter version.

When you connect this thermistor in series with a 3300Ω resistor to +3.3V DC, you can measure temperature on a microcontroller's analog input pin. The following values have been read:

Temp. (°C)	Resistance (Ω)	Measured Voltage
-55	490	0.42665
-50	515	0.44548
-40	567	0.48386
-30	624	0.52477
-20	684	0.56657
-10	747	0.60912
0	815	0.65358
+10	886	0.69847
+20	961	0.74426
+25	1000	0.76744
+30	1040	0.79078
+40	1122	0.83731
+50	1209	0.88483
+60	1299	0.93209
+70	1392	0.97903
+80	1490	1.02651
+90	1591	1.07346
+100	1696	1.12026
+110	1805	1.16680
+120	1915	1.21179
+125	1970	1.23359
+130	2023	1.25416
+140	2124	1.29226
+150	2211	1.32395

The following is MMBASIC demo code that runs on a DuinoMite board with the sensor connected to Pin 1 and with a 3300Ω resistor in series. It displays the average of 1000 readings (to four decimal places), then repeats.

 5 OPTION BASE 0
 10 DATA -55,0.42665,-50,0.44548,-40,0.48386,-30,0.52477,-20,0.56657,-10,0.60912,0,0.65358,+10,0.69847
 20 DATA +20,0.74426,+25,0.76744,+30,0.79078,+40,0.83731,+50,0.88483,+60,0.93209,+70,0.97903,+80,1.02651
 30 DATA +90,1.07346,+100,1.12026,+110,1.16680,+120,1.21179,+125,1.23359,+130,1.25416,+140,1.29226,+150,1.32395
 40 DIM T(23),V(23)
 50 FOR I = 0 TO 23: READ T(I): READ V(I): NEXT I
 60 SETPIN 1,1
 70 NRD = 1000 'number of times to read
 100 'read temperature
 110 VOL = 0
 120 FOR I = 1 TO NRD: VOL = VOL + PIN(1): NEXT I: VOL = VOL / NRD
 130 IF VOL < V(0) OR VOL > V(23) THEN 180
 140 I = 0
 150 DO
 160 IF VOL > V(I) THEN I = I + 1 ELSE GOTO 200
 170 UNTIL (I=23)
 180 PRINT "ALARM – TEMPERATURE OUTSIDE -55+150C"
 200 TEMP = T(I)-(V(I)-VOL)*(T(I)-T(I-1))/(V(I)-V(I-1))
 210 PRINT "TEMPERATURE IS:"; TEMP
 220 GOTO 100