Fluctuate TMP 36 in negative with arduino uno

Hi Everyone,

Can you help me as I used TMP 36 with Arduino uno its working perfectly in Positively like milli volts = 743 Temperature in C = 24.3 milli volts = 753 Temperature in C = 25.3 milli volts = 743 Temperature in C = 24.3 milli volts = 733 Temperature in C = 23.3 milli volts = 753 Temperature in C = 25.3 milli volts = 748 Temperature in C = 24.8 milli volts = 743 Temperature in C = 24.3 milli volts = 738 Temperature in C = 23.8 milli volts = 748 Temperature in C = 24.8 milli volts = 748 Temperature in C = 24.8 milli volts = 748 Temperature in C = 24.8 milli volts = 758 Temperature in C = 25.8 milli volts = 748 Temperature in C = 24.8 milli volts = 743 Temperature in C = 24.3 milli volts = 743 Temperature in C = 24.3

but fluctuate in negative temperature i.e. when I sense tmp 36 with ice cube it shows reading like this

milli volts = 714 Temperature in C = 21.4 milli volts = 699 Temperature in C = 19.9 milli volts = 469 Temperature in C = -3.1 milli volts = 352 Temperature in C = -14.8 milli volts = 464 Temperature in C = -3.6 milli volts = 689 Temperature in C = 18.9 milli volts = 645 Temperature in C = 14.5 milli volts = 401 Temperature in C = -9.9 milli volts = 313 Temperature in C = -18.7 milli volts = 621 Temperature in C = 12.1 milli volts = 684 Temperature in C = 18.4 milli volts = 367 Temperature in C = -13.3 milli volts = 337 Temperature in C = -16.3 milli volts = 572 Temperature in C = 7.2 milli volts = 499 Temperature in C = -0.1 milli volts = 611 Temperature in C = 11.1 milli volts = 274 Temperature in C = -22.6 milli volts = 513 Temperature in C = 1.3 milli volts = 567 Temperature in C = 6.7 milli volts = 489 Temperature in C = -1.1 milli volts = 494 Temperature in C = -0.6 milli volts = 166 Temperature in C = -33.4 milli volts = 606 Temperature in C = 10.6 milli volts = 557 Temperature in C = 5.7 milli volts = 78 Temperature in C = -42.2 milli volts = 367 Temperature in C = -13.3 milli volts = 591 Temperature in C = 9.1 milli volts = 371 Temperature in C = -12.9 milli volts = 259 Temperature in C = -24.1 milli volts = 479 Temperature in C = -2.1 milli volts = 587 Temperature in C = 8.7 milli volts = 518 Temperature in C = 1.8 milli volts = 323 Temperature in C = -17.7 milli volts = 455 Temperature in C = -4.5 milli volts = 567 Temperature in C = 6.7 milli volts = 469 Temperature in C = -3.1 milli volts = 611 Temperature in C = 11.1 milli volts = 596 Temperature in C = 9.6 milli volts = 489 Temperature in C = -1.1 milli volts = 323 Temperature in C = -17.7 milli volts = 381 Temperature in C = -11.9 milli volts = 552 Temperature in C = 5.2 milli volts = 230 Temperature in C = -27.0 milli volts = 337 Temperature in C = -16.3 milli volts = 606 Temperature in C = 10.6 milli volts = 425 Temperature in C = -7.5 milli volts = 401 Temperature in C = -9.9 milli volts = 606 Temperature in C = 10.6 milli volts = 484 Temperature in C = -1.6 milli volts = 503 Temperature in C = 0.3 milli volts = 626 Temperature in C = 12.6 milli volts = 665 Temperature in C = 16.5 milli volts = 503 Temperature in C = 0.3 milli volts = 249 Temperature in C = -25.1 milli volts = 587 Temperature in C = 8.7 milli volts = 1168 Temperature in C = 66.8 milli volts = 528 Temperature in C = 2.8 milli volts = 249 Temperature in C = -25.1 milli volts = 626 Temperature in C = 12.6 milli volts = 670 Temperature in C = 17.0 milli volts = 562 Temperature in C = 6.2 milli volts = 283 Temperature in C = -21.7 milli volts = 230 Temperature in C = -27.0 milli volts = 630 Temperature in C = 13.0 milli volts = 357 Temperature in C = -14.3 milli volts = 352 Temperature in C = -14.8 milli volts = 288 Temperature in C = -21.2 milli volts = 518 Temperature in C = 1.8 milli volts = 650 Temperature in C = 15.0 milli volts = 445 Temperature in C = -5.5 milli volts = 215 Temperature in C = -28.5 milli volts = 552 Temperature in C = 5.2 milli volts = 552 Temperature in C = 5.2 milli volts = 523 Temperature in C = 2.3 milli volts = 797 Temperature in C = 29.7 milli volts = 684 Temperature in C = 18.4 milli volts = 582 Temperature in C = 8.2 milli volts = 557 Temperature in C = 5.7 milli volts = 714 Temperature in C = 21.4 milli volts = 802 Temperature in C = 30.2 milli volts = 459 Temperature in C = -4.1 milli volts = 376 Temperature in C = -12.4 milli volts = 728 Temperature in C = 22.8 milli volts = 665 Temperature in C = 16.5 milli volts = 381 Temperature in C = -11.9 milli volts = 288 Temperature in C = -21.2 milli volts = 674 Temperature in C = 17.4 milli volts = 543 Temperature in C = 4.3 milli volts = 279 Temperature in C = -22.1 milli volts = 528 Temperature in C = 2.8 milli volts = 660 Temperature in C = 16.0 milli volts = 528 Temperature in C = 2.8 milli volts = 455 Temperature in C = -4.5 milli volts = 538 Temperature in C = 3.8

and here is my program

const int analogIn = A0;

int RawValue= 0; double Voltage = 0; double tempC = 0;

void setup() { Serial.begin(9600); }

void loop() {

RawValue = analogRead(analogIn); Voltage = (RawValue / 1023.0) * 5000; // 5000 to get millivots. tempC = (Voltage-500) * 0.1; // 500 is the offset

Serial.print("\t milli volts = "); // shows the voltage measured Serial.print(Voltage,0); Serial.print("\t Temperature in C = "); Serial.println(tempC,1); delay(2000); }

I want to know in negative why this happened ? what the mistake I do ? kindly tell me.

thanks in advance

Depends how you do the "with ice cube" part. You may not be measuring what you think you measure.

Normally you'd take a beaker, fill it with ice and water, and let it sit for a while. Melting ice is 0°C.

Otherwise stick the sensor in your freezer, wires out of the door, and see what happens.

Both should give a pretty stable result.

Don't get the leads wet though - could that be the issue?