How to Pick the Best Temperature and Humidity Sensor for Your Arduino Project

What this blog is about:

Basic about temperature & humidity Sensor

First of all, let us figure out a basic question “Why do we need a temperature and humidity sensor”.

Well, humidity and temperature are closely related from the physical quantity itself to the actual people’s lives.

• Temperature
  We all know about temperature, it is one of the 7 basic physical quantities in the International System of Units, and it is a physical quantity used to measure the degree of heat and coldness of objects.

• Humidity
  Then, what about humidity? Humidity is the concentration of water vapour present in the air. The relative humidity of air is commonly used in life, expressed in %RH. Relative humidity is closely related to temperature. For a certain volume of sealed gas, the higher the temperature, the lower the relative humidity, and the lower the temperature, the higher the relative humidity.

The temperature and humidity of people’s environment will directly affect people’s body temperature regulation function and heat conduction effect. It will further affect the thinking activity and mental state, thus affecting the efficiency of our study and work. Therefore, we need temperature and humidity sensors

Common temperature & humidity sensors for Arduino

In this part we will list the most common temperature and humidity sensors which are suitable for Arduino Project.

DHT11

 

 

When we talk about temperature and humidity sensor, DHT series is the most common used. They are all automatically calibrated, very easy to use and have a very good Arduino software library, which is very popular with maker. Let’s see what DHT11 capable of.

The old DHT11

Item	Value
Operating Voltage	DC：3.3-5.5V
Temperature Range	0~+50℃
Humidity Range	20~95%RH
Temperature Accuracy	±2℃
Humidity Accuracy	±5%RH
Sensor Type	Resistive humidity sensor

The measurement range of DHT11 is not wide, and the measurement accuracy is not high. Commonly used in some junior projects.

The good news is that, there is an updated version of DHT11. The manufacturer replaced resistive humidity sensor with capacitive humidity sensor and the new DHT11 is much more better in measurement range.

The new DHT11

Item	Value
Operating Voltage	DC：3.3-5.5V
Temperature Range	-20~+60℃
Humidity Range	5~95%RH
Temperature Accuracy	±2℃
Humidity Accuracy	±5%RH
Sensor Type	Capacitive humidity sensor

So where can I buy a new version of DHT11?

Well, as far as we know the Grove – Temperature & Humidity Sensor (DHT11) from Seeed is based on the New version.

DHT22/AM2302

DHT22 is a high-end model in the DHT series, also known as AM2302 or RHT03. It has a wide measurement range and high measurement accuracy.

Item	Value
Operating Voltage	DC：3.3-5.5V
Temperature Range	-40~+80℃
Humidity Range	0~99.9%RH
Temperature Accuracy	±0.5℃
Humidity Accuracy	±2%RH
Sensor Type	Capacitive humidity sensor

DHT22 has excellent long-term stability and can be used in medical, meteorological and other professional fields

AM2311A

The AM2311A digital temperature and humidity module is a temperature and humidity compound sensor with calibrated digital signal output. It uses special digital module acquisition technology and temperature and humidity sensing technology to ensure that the product has extremely high reliability and excellent long-term stability.

Item	Value
Operating Voltage	DC：3.3-5.5V
Temperature Range	-40~+80℃
Humidity Range	0~99.9%RH
Temperature Accuracy	±0.5℃
Humidity Accuracy	±3%RH
Sensor Type	Capacitive humidity sensor

AHT20

AHT20 is a recently released industrial grade temperature and humidity sensor. Its humidity measurement range reaches an astonishing 0-100%RH! The new MEMS capacitive humidity sensing element makes it have far better performance than traditional capacitive sensors.

Item	Value
Operating Voltage	DC：2.0-5.5V
Temperature Range	-40~+85℃
Humidity Range	0~100%RH
Temperature Accuracy	±0.3℃
Humidity Accuracy	±2%RH
Sensor Type	MEMS semiconductor capacitive humidity sensing element

How to select the best one suit for your project

Different temperature and humidity sensors have large performance differences and large price differences. So how to choose the most suitable sensor for your project?

• Measure Range

As with the measurement of weight and temperature, the selection of the humidity sensor must first determine the measurement range. Except for meteorological and scientific research departments, temperature and humidity measurement and control generally do not require full humidity (0-100% RH) measurement. Generally speaking, the wider the range and the higher the price, just choose the range that meets your project needs.

• Humidity Accuracy

The accuracy of measurement is the most important index of the humidity sensor. For every percentage point increase, it is a step or even a grade for the humidity sensor. Because different precisions are to be achieved, their manufacturing costs vary greatly, and their selling prices vary widely.

In normal projects, DHT11 is sufficient. The measurement range of 5 ~ 95% RH will satisfy most applications.

If your arduino project needs a wider measurement range and higher accuracy, such as medical, weather station, then we recommend DHT22.

If the interference is strong and the environment is harsh, AM2311A will be a good choice.

When your project requires industrial-grade sensors, then there is no doubt that AHT20 will be very suitable.