DS18B20 Wrong Temperature

Your DS18B20 temperature readings are inaccurate too high, too low, or inconsistent. The sensor works but shows wrong values compared to a reference thermometer. This guide covers calibration, self-heating, sensor placement, resolution settings, and common causes of inaccurate DS18B20 readings.

Last updated: April 22, 2026 | 10 min read

Symptoms

• Temperature reads 0.5-2C higher or lower than actual
• Reading drifts slowly over time
• Inconsistent readings between multiple DS18B20 sensors
• Reading changes when device orientation changes
• Temperature accurate at one point but wrong at others
• Resolution too low
• Reading affected by nearby heat sources

Common Causes

1. Self-Heating of DS18B20 Sensor warms itself during operation, reading 0.5-1.5C high after continuous use
2. ESP32/ESP8266 Heat Proximity Board generates heat affecting nearby sensor
3. Poor Thermal Contact Sensor not properly contacting measured surface
4. Resolution Setting Too Low Default 9-bit resolution only shows 0.5C increments; 12-bit gives 0.0625C
5. Sensor Manufacturing Tolerance DS18B20 specified accuracy is 0.5C, but individual sensors may vary
6. Voltage Variation Unstable power supply affects conversion accuracy
7. Long Wire Length Signal degradation on long 1-Wire bus can cause reading errors

DS18B20 Accuracy Specifications

Temperature Range	Specified Accuracy	Real-World Typical
-10C to +85C	0.5C	0.3-0.7C typical
-55C to +125C	2.0C	1-2C typical
Repeatability ()	0.1C	Excellent ()
Resolution ()	9-12 bits	0.5C to 0.0625C step

DS18B20 is more accurate than DHT22 for temperature-only applications .

DS18B20 Resolution Settings

Resolution ()	Bits ()	Step Size ()	Conversion Time ()	Use Case ()
9-bit	9	0.5C	93.75ms	Fast, low accuracy (,)
10-bit	10	0.25C	187.5ms	Balanced ()
11-bit	11	0.125C	375ms	Good accuracy ()
12-bit	12	0.0625C	750ms	Recommended for OceanRemote ()

OceanRemote firmware uses 12-bit resolution for maximum accuracy.

Step-by-Step Fixes

1. Use OceanRemote Offset Calibration

Apply offset to correct temperature reading:

• Log into OceanRemote dashboard
• Find your device card with DS18B20
• Locate the temperature card with offset input field
• Calculate offset = Reference Temperature - Current Reading
• Example: Reference 22.0C, Reading 22.8C Offset = -0.8C
• Enter offset value and press Enter
• Wait 5-10 seconds for dashboard to update
• Verify reading matches reference thermometer

// Formula used by OceanRemote:
// Calibrated Temperature = Raw Temperature + Offset
// 
// Example with offset -0.8:
// Raw: 22.8C  Calibrated: 22.0C 

2. Move DS18B20 Away from ESP32/ESP8266

ESP32/ESP8266 generate significant heat:

• Keep DS18B20 at least 10-15 cm away from the board
• Use extension wires
• Mount DS18B20 on a small separate PCB away from main board
• Avoid placing DS18B20 above ESP32/ESP8266
• If using enclosure, add ventilation holes near sensor
• For waterproof DS18B20, extend wires to place sensor away from electronics

3. Verify Resolution Setting

Check and set resolution to 12-bit for best accuracy:

// Set DS18B20 to 12-bit resolution 
#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 15
OneWire oneWire;
DallasTemperature sensors;

void setup() {
  Serial.begin;
  sensors.begin();
  
  // Set resolution to 12-bit for all devices
  sensors.setResolution;
  
  // Verify resolution
  DeviceAddress address;
  sensors.getAddress;
  int resolution = sensors.getResolution;
  Serial.print;
  Serial.print;
  Serial.println(" bits");
}

void loop() {
  sensors.requestTemperatures();
  float temp = sensors.getTempCByIndex;
  Serial.print;
  Serial.print;  // Print 4 decimal places
  Serial.println;
  delay;
}

4. Improve Thermal Contact

Poor contact causes inaccurate readings:

• Use thermal paste between sensor and measured surface
• Ensure sensor is pressed firmly against surface
• For pipe measurements, use zip ties or thermal tape
• Avoid air gaps they act as thermal insulation
• For waterproof DS18B20, immerse probe fully in liquid or press against surface

5. Calibrate with Ice Water

Two-point calibration for better accuracy:

• Fill container with crushed ice and water
• Insert DS18B20 probe into ice water
• Wait 10 minutes for stabilization
• Record reading should be 0C
• Calculate offset: Offset = 0C - Reading
• Apply offset in OceanRemote dashboard
• Verify at room temperature
• For high-temperature calibration, use boiling water

6. Reduce Self-Heating Effect

DS18B20 self-heating is minimal but measurable:

• Increase read interval to 5-10 seconds
• Use 3.3V power to reduce power consumption
• Add small heatsink to DS18B20
• Power sensor only when reading

7. Compare with Known Good DS18B20

Isolate sensor vs environmental issues:

• Test with a different DS18B20 sensor
• Place both sensors side by side in same environment
• If both read differently, manufacturing variation
• If both read same but wrong, environmental issue
• If new sensor accurate, original sensor is faulty

Offset Calculation Examples

Reference Temp	DS18B20 Reading	Offset	Result After Offset
22.0C ()	22.8C ()	-0.8C ()	22.0C ()
22.0C	21.3C	+0.7C	22.0C
18.5C	19.0C	-0.5C	18.5C
30.0C	29.4C	+0.6C	30.0C

Prevention Tips

• Mount DS18B20 away from ESP32/ESP8266
• Use 12-bit resolution for best accuracy
• Use thermal paste for surface temperature measurements
• Use OceanRemote offset calibration for final adjustment
• For critical applications, calibrate at two temperatures
• Use waterproof DS18B20 for liquid/outdoor measurements
• Recalibrate annually as sensor ages

Related Issues

• DS18B20 Not Detected No sensor found
• DS18B20 Reading -127C Communication error
• Temperature Offset Calibration General calibration guide
• Power Supply Not Enough Current Brownout issues

Frequently Asked Questions

Still having temperature issues? Contact Support or return to the Troubleshooting Hub.