# Tempreture Measurement with HCSR04 Ultrasonic Sensor **URL:** \ **Category:** Programming\ **Created:** [January 10, 2025, 7:57am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030 "2025-01-10T07:57:25Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![strawhatt](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@strawhatt](https://forum.arduino.cc/u/strawhatt)\ **Post date:** [January 10, 2025, 7:57am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/1 "2025-01-10T07:57:25Z")
Hi. I am trying to make a project with HCSR04 Sensor in unconventional way. What i want is measure the temperature with HCSR04 Ultrasonic Sensor. Ultrasonic Sensor works with sound waves to detect distance measurement. ```arduino digitalwrite(trig, LOW); delayMicroseconds(2); digitalwrite(trig,HIGH); delayMicroseconds (10); time= pulseIn(echo, HIGH) ; ``` So i know the time. I fix the sensor so that it is 10cm away from the wall for calculate the speed of voice. ```arduino distance = 10; speedOfVoice= (2*distance)/time; ``` Far now, i get the time and speedOfVoice while the sensor is fixed to 10cm away from wall. I need these calculations because; `temperature = (speedOfSound-0.03314)/0.0000606` So i should have calculate the temperature with these equations but i dont know where i make mistake. What shluld i do? ---
**Author:** ![UKHeliBob](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/ukhelibob/32/215663_2.png) [@UKHeliBob](https://forum.arduino.cc/u/UKHeliBob)\ **Post date:** [January 10, 2025, 8:11am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/2 "2025-01-10T08:11:22Z")
Welcome to the forum Please post your full sketch ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 10, 2025, 8:31am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/3 "2025-01-10T08:31:50Z")
> [@strawhatt](#): > > ```arduino > distance = 10; > speedOfVoice= (2*distance)/time; > > ``` This will calculate the speed of sound in units of centimetres per microsecond. > [@strawhatt](#): > > temperature = (speedOfSound-0.03314)/0.0000606 What units for speed of sound does this equation require in order to give the correct result as a temperature in C or F? > [@strawhatt](#): > > i dont know where i make mistake You are implying that you have made a mistake. What evidence do you have for this mistake? That would have been a very helpful thing to include in your original post ---
**Author:** ![StefanL38](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/stefanl38/32/713548_2.png) [@StefanL38](https://forum.arduino.cc/u/StefanL38)\ **Post date:** [January 10, 2025, 10:35am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/4 "2025-01-10T10:35:48Z")
you get the traveltime in µseconds. Example for a temperature of 18°C speed of sound is 331.5 + 0.6 \* 18 = 342,3 m/sec traveltime for a distance of 0.2 m t = 0.2 m / 342.3 m/sec = 584 µsec. 584 µsec is the time that you measure t = t = distance / V(T) = distance / (331.5 m/sec + 0.6 m/ (sec_K) \* T t = distance / (331.5 m/sec + 0.6 m/(sec_K) \*T transforming the equation to T (Temperature) Temperature T = ( (D / t) - 331.5) \* 10 / 6 With "standard"-units like m you would get a float-calculation Temperature T = (0.2 / (584.0/1000000.0) - 331.5) \* 10.0 / 6.0 which might be unprecise as floats in C++ do not have many digits So using bigger numbers to do the calculation with integers might be more precise unsigned longs can hold values up to 2^32 = 4\_294\_967\_296 to make the division D / t more precise the numbers can be multiplied by 1000 / 100 should give the temperature ```arduino unsigned long dfactor = 1000; unsigned long zfactor = 100; unsigned long speedOfSoundAt0C = 3315UL * zfactor; // 123456 // 200000 µm * 1000 = 200_000_000 // 1234567890 // 4294967296 unsigned long distance = 200000UL * dfactor; unsigned long travelTime = 584UL; unsigned long temperature = 0; float FspeedOfSoundAt0C = 331.5; float Fdistance = 0.2; float FtravelTime = 584.0 / 1000000; float Ftemperature = 0.0; void setup() { Serial.begin(115200); Serial.println("Setup-Start"); temperature = ( ( (distance ) / travelTime) - (speedOfSoundAt0C) ) * 10 / 6; Serial.print("integer-calc temperature="); Serial.println(temperature / 1000.0,6); Ftemperature = ( (Fdistance/ FtravelTime - FspeedOfSoundAt0C) * 10.0 ) / 6.0; Serial.print("float-calc Ftemperature="); Serial.println(Ftemperature,6); } void loop() { // put your main code here, to run repeatedly: } ``` Serial output shows no big difference ```arduino Setup-Start integer-calc temperature=18.274999 float-calc Ftemperature=18.276266 ``` > **[Test-integer-versus-float-Calc-001 - Wokwi ESP32, STM32, Arduino Simulator](https://wokwi.com/projects/419692519011105793)** > > Run IoT and embedded projects in your browser: ESP32, STM32, Arduino, Pi Pico, and more. No installation required! ---
**Author:** ![alto777](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/alto777/32/317385_2.png) [@alto777](https://forum.arduino.cc/u/alto777)\ **Post date:** [January 10, 2025, 12:05pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/5 "2025-01-10T12:05:11Z")
> [@StefanL38](#): > > 3\_315\_000\_000 Commas are used in regular writing when dealing with large numbers. There is no need to introduce a new character for that purpose. 3,315,000,000 a7 ---
**Author:** ![strawhatt](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@strawhatt](https://forum.arduino.cc/u/strawhatt)\ **Post date:** [January 10, 2025, 12:27pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/6 "2025-01-10T12:27:06Z")
i will try this code now sorry for late reply. Here is my code. ```arduino #include #include #include ///// #define SDA_PORT PORTC #define SDA_PIN 4 // A4 #define SCL_PORT PORTC #define SCL_PIN 5 // A5 #define I2C_FASTMODE 1 #include #include "OLED_SoftI2C.h" #include "term8x14_font.h" #include OLEDSoftI2C oled(0x3c); char txt[10]; ///// #define OLED_RESET 5 #define echoPin 6 #define trigPin 7 // LM35 Sıcaklık Sensörü için Tanımlamalar int lm35Pin = A0; int lm35Val = 0; // HC-SR03 Sensörü için Tanımlamalar float maximumRange=400.0; float minimumRange=0.0; float temp_voltage ; float temp; Adafruit_SSD1306 display(OLED_RESET); void setup() { pinMode(trigPin,OUTPUT); pinMode(echoPin,INPUT); //// oled.init(); oled.clrScr(); oled.setFont(Term8x14PL); oled.printStr(0, 0, "LM35:"); oled.printStr(0, 4, "HCSR:"); oled.setMinCharWd(8); ///// Serial.begin(9600); } float tempHCSR(float distance) { float speedOfSound, measuredHCSR_temp, cm; long durationHCSR; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(10); durationHCSR = pulseIn(echoPin, HIGH); cm = ((durationHCSR / 2.0) * 0.0343); // Ses hızını hesapla (m/s) speedOfSound = (2.0 * (distance)) / (durationHCSR); Serial.println(durationHCSR); Serial.println(cm); Serial.println(speedOfSound); // Sıcaklığı hesapla //sicaklikHCSR = (sesHizi - 0.03314) / 0.0000606; measuredHCSR_temp = (speedOfSound*10000.0-331.4)/0.6; return measuredHCSR_temp; } void loop() { float measuredHCSR_temp = tempHCSR(28.96); lm35Val = analogRead(lm35Pin); temp_voltage = (5.0/1023.0)*lm35Val; temp = temp_voltage /0.01; Serial.println(temp); Serial.println(measuredHCSR_temp); dtostrf(temp,5,2,txt); oled.printStr(38,0,txt); dtostrf(measuredHCSR_temp,5,2,txt); oled.printStr(38,4,txt); delay(200); } ``` i was using this code to calcualte temperature. ---
**Author:** ![robtillaart](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robtillaart/32/1098811_2.png) [@robtillaart](https://forum.arduino.cc/u/robtillaart)\ **Post date:** [January 10, 2025, 12:27pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/7 "2025-01-10T12:27:37Z")
Used the SRF04 (compatible) with temperature and humidity compensation. There is a table how to compensate for T and H and some links in the repo > **[GitHub - RobTillaart/SRF05: Arduino library for SRF05 distance sensor](https://github.com/RobTillaart/SRF05)** > > Arduino library for SRF05 distance sensor related docs posted recently here > [@Advices to improve this simple DHT11 data read, or next steps ?](https://forum.arduino.cc/t/advices-to-improve-this-simple-dht11-data-read-or-next-steps/1340007/12): > > I'm currently looking into Arden\_Buck\_equation Interesting Then to calculate the speed of sound accurately, assuming one can find or derive the effect of water pressure (which is small, but this is for fun only.) Did some work there - [GitHub - RobTillaart/SRF05: Arduino library for SRF05 distance sensor](https://github.com/RobTillaart/SRF05) These might be interesting reads [82084136.pdf](https://forum.arduino.cc/uploads/short-url/eHilbTSHhj7Dv95vnOpxcGKcPtd.pdf) (729.5 KB) [Environmental\_effects\_on\_the\_speed\_of\_sound.pdf](https://forum.arduino.cc/uploads/short-url/1bCtF5ea5Efp0Uvt1zy06YLLhpr.pdf) (812.5 KB) ---
**Author:** ![strawhatt](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@strawhatt](https://forum.arduino.cc/u/strawhatt)\ **Post date:** [January 10, 2025, 12:35pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/8 "2025-01-10T12:35:39Z")
Thanks but i am trying to measure the temperature with HCSR04 from speed of sound and distance. I am not trying to make pricise the measurement of sensor. ---
**Author:** ![StefanL38](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/stefanl38/32/713548_2.png) [@StefanL38](https://forum.arduino.cc/u/StefanL38)\ **Post date:** [January 10, 2025, 12:52pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/9 "2025-01-10T12:52:44Z")
Had some errors in my first posting. Now evyrthing is correct. I did not analyse your calculation. For my my demo-code I calculated speed of sound for 18°C. 342.5 m/sec Then calulated traveltime for 0.2 m 584 µsec And then calculated back to temperature with these values and got 18.28°C (instead of 18.00°C) Calcuation-code ```arduino float FspeedOfSoundAt0C = 331.5; float Fdistance = 0.2; float FtravelTime = 584.0 / 1000000; float Ftemperature = 0.0; Ftemperature = ( (Fdistance/ FtravelTime - FspeedOfSoundAt0C) * 10.0 ) / 6.0; ``` ---
**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\ **Post date:** [January 10, 2025, 12:55pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/10 "2025-01-10T12:55:47Z")
> [@strawhatt](#): > > temperature You can not measure temperature. What you CAN do is measure the speed of sound and interpolate, which travels at a known speed in an environment of known altitude, pressure and temperature. You know the distance from your transmitter to your reflector. As the temperature changes, so will the time to receive the reflection. See @StefanL38 @robtillaart @PaulRB replies. ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 10, 2025, 12:56pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/11 "2025-01-10T12:56:13Z")
You may need to take many distance measurements and average them to remove random noise from the readings. Even then, on most Arduino, pulseIn() may not be accurate to 1us, I'm not sure. If it is only actuate to, say 4us, then your temp readings will only be accurate to 4~5 degrees C. ---
**Author:** ![StefanL38](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/stefanl38/32/713548_2.png) [@StefanL38](https://forum.arduino.cc/u/StefanL38)\ **Post date:** [January 10, 2025, 1:07pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/12 "2025-01-10T13:07:38Z")
I made the calculations ```arduino float-calc Ftemperature=18.276266 float-calc 4 µsec too short Ftemperature=22.212677 float-calc 4 µsec too long Ftemperature=14.393413 ``` ups pretty big difference So increasing the disctance will have longer traveltimes and a smaller error with the 4 µsec unprecision/inaccuracy. Still a **very** interesting project with a lot of opportunities to learn about programming, engineering and science ---
**Author:** ![robtillaart](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robtillaart/32/1098811_2.png) [@robtillaart](https://forum.arduino.cc/u/robtillaart)\ **Post date:** [January 10, 2025, 1:39pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/13 "2025-01-10T13:39:23Z")
> [@StefanL38](#): > > traveltime for a distance of 0.2 m > > t = 0.2 m / 342.3 m/sec = 584 µsec. just a side note: In terms of accuracy/precision recall that ```arduino 340 m/sec == 340 mm / millisec == 0.34 mm / microsec. ``` So an Arduino UNO which has a resolution of 4 us equals 1.4 mm. ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 10, 2025, 5:32pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/14 "2025-01-10T17:32:30Z")
I may be crying wolf. I remember that on Uno/Nano 3/Mega (16MHz AVR MCUs) the micros() function is only accurate to about 4us. However, I also seem to remember that pulseIn() does not rely on micros() but rather uses a tight loop that increments a count during the pulse. That count is then converted microseconds using a calibrated constant. So maybe it is accurate to 1us. ---
**Author:** ![robtillaart](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robtillaart/32/1098811_2.png) [@robtillaart](https://forum.arduino.cc/u/robtillaart)\ **Post date:** [January 10, 2025, 7:41pm UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/15 "2025-01-10T19:41:55Z")
> [@PaulRB](#): > > However, I also seem to remember that pulseIn() does not rely on micros() but rather uses a tight loop that increments a count during the pulse. That count is then converted microseconds using a calibrated constant. So maybe it is accurate to 1us. 100%, in fact its core is written in assembler IIRC. What pulseIn does not do is disabling interrupts so there is a chance it gets disrupted e.g. if you do a Serial.print("whatever"); just before the call of pulseIn. So I think for precise measurements I would add `noInterrupts() or cli()` before PulseIn(), To investigate... micros() is hardware timer based so it will "count" even during interrupts, price is its 4us resolution. ---
**Author:** ![strawhatt](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@strawhatt](https://forum.arduino.cc/u/strawhatt)\ **Post date:** [January 12, 2025, 1:53am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/16 "2025-01-12T01:53:42Z")
Well I made some progress on project and already made the presentation to my advisor prof. I will share the code here and hope that it works for you guys too. It is not precise but if you can compansite the errors on HC-SR04 sensor with bm280 it would be work better. Compansite is important because the speed of sound also depends to the temp, humidity and presure. If you do the calibration of these, you can measure the Temp from HC-Sr04 more precisely. Here is the code and other Lib Files; ```arduino #include #include #include ///// #define SDA_PORT PORTC #define SDA_PIN 4 // A4 #define SCL_PORT PORTC #define SCL_PIN 5 // A5 #define I2C_FASTMODE 1 #include // These #include "OLED_SoftI2C.h" // Are #include "term8x14_font.h" // For #include // OLED OLEDSoftI2C oled(0x3c); // Display char txt[100]; ///// #define OLED_RESET 5 #define echoPin 6 #define trigPin 7 // LM35 Temp Sensor int lm35Pin = A0; int lm35Val = 0; // HC-SR03 Sensor double temp_voltage ; double temp; Adafruit_SSD1306 display(OLED_RESET); void setup() { pinMode(trigPin,OUTPUT); // pin7 pinMode(echoPin,INPUT); //// oled.init(); oled.clrScr(); oled.setFont(Term8x14PL); oled.printStr(0, 0, "LM35:"); oled.printStr(0, 4, "HCSR:"); oled.setMinCharWd(8); ///// Serial.begin(9600); } double tempHCSR(float distance) { double speedOfSound, measuredHCSR_temp ; long durationHCSR; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(2); // Getting the value of pulse duration for speed of sound durationHCSR = pulseIn(echoPin, HIGH); // Speed of Sound Calculation (m/s) speedOfSound = (2.0 * (distance)) / (durationHCSR); Serial.println(durationHCSR); Serial.println(speedOfSound); // Calculating the HC-SR04 Temp measuredHCSR_temp = (speedOfSound - 0.03314) / 0.0000606; // (Celsius) //measuredHCSR_temp = (speedOfSound*10000.0-331.4)/0.6; return measuredHCSR_temp; } void loop() { float measuredHCSR_temp = tempHCSR(20.0); // write the distance of wall to inside(dont change the distance while trying to get temp. Sensor has to be fixed.) delay(20); lm35Val = analogRead(lm35Pin); // getting the true temp value analog delay(20); temp_voltage = (5.0/1023.0)*lm35Val; temp = temp_voltage /0.01; Serial.println(temp); Serial.println(measuredHCSR_temp); // OLED Displays dtostrf(temp,5,2,txt); oled.printStr(38,0,txt); dtostrf(measuredHCSR_temp,5,2,txt); oled.printStr(38,4,txt); delay(2000); } ``` [term8x14\_font.h](https://forum.arduino.cc/uploads/short-url/xtlSpeWc7dnuebdHBNZSGZ3aq2U.h) (13.6 KB) [OLED\_SoftI2C.h](https://forum.arduino.cc/uploads/short-url/fYhpoLj2C5OpWNAFUVdRgDL1122.h) (6.9 KB) ---
**Author:** ![robtillaart](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robtillaart/32/1098811_2.png) [@robtillaart](https://forum.arduino.cc/u/robtillaart)\ **Post date:** [January 20, 2025, 11:01am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/17 "2025-01-20T11:01:41Z")
thanks for sharing the result > [@strawhatt](#): > > I made some progress on project and already made the presentation to my advisor prof. Just wondering, is the forum (thread) mentioned in your "used resources" list? ---
**Author:** ![strawhatt](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@strawhatt](https://forum.arduino.cc/u/strawhatt)\ **Post date:** [January 21, 2025, 10:38am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/18 "2025-01-21T10:38:18Z")
1xArduino Uno 1xHC-SR04 Ultrasonic Distance Measurement Sensor 1xLM35 Temperature Sensor 1x 0.96 Inch I2C Oled Display Module Cables and Breadboard for connections. You can see the connections if you check the code. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [July 20, 2025, 10:38am UTC](https://forum.arduino.cc/t/tempreture-measurement-with-hcsr04-ultrasonic-sensor/1341030/19 "2025-07-20T10:38:25Z")
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