Comparative evaluation of ultra-small volume temperature and humidity modules HTU21 and SHT21

Ultra-small volume integrated temperature and humidity digital output module is widely used in mobile phones, communications, HVAC, medical, environmental monitoring, household appliances, control boards, etc. due to its small size and high accuracy. Apollo took samples of the two most commonly used HTU21 and SHT21 products on the market and made a detailed comparative evaluation of these two products. This evaluation focuses on the analysis of cost performance, performance, power consumption, etc. for For your reference.

HTU21

1. Features of HTU21D.

Based on high-performance humidity sensing elements, the new generation HTU21D temperature and humidity sensor has set a new standard in terms of size and intelligence: it is embedded in a dual-row flat no-lead DFN package suitable for reflow soldering. mm. The sensor outputs a calibrated digital signal in standard I2C format. Diversified output methods, wide operating voltage range, and high temperature accuracy and humidity accuracy. HTU21 series modules are designed for low-power and small-volume applications. They have the advantages of good quality, fast response speed, strong anti-interference ability, high cost performance, etc. The small size (3x3mm) and extremely low power consumption make HTU21D a variety of Choice of application.

2. Comparison of important parameters of HTU21 and SHT21 sensors:

It can be seen from the above chart comparison:

Although the general parameters of HTU21D and SHT21 are similar, HTU21D has some advantages: a wider supply voltage range (1.5V-3.6V), lower power consumption (2.7uW) than SHT21, HTU21D has a humidity of ± 2% RH The accuracy is higher than SHT20 (± 3.5% RH), which is equivalent to SHT21 (± 2% RH), but the price is cheaper than SHT21, and the response time of 5S is also faster.

3. The dimensions of HTU21D are as follows:

1) Sensor size:

Note: The size unit is mm, the tolerance is ± 0.1mm, and the bottom of the sensor has been grounded.

2) Back of sensor electrode and dimension drawing

Footprint of HTU21D, unit: mm

4. Comparison of appearance and pins of HTU21D and SHT21

In terms of appearance size, foot distribution and definition, HTU21D and SHT21 are exactly the same, and pin to pin replacement can be realized directly, as shown below:

HTU21D SHT21

5. HTU21D and SHT21 software:

HTU21D and SHT21 are both I2C interface digital outputs and have the same start and stop signal timing:

· Start signal

When the transmission is started and a bit of data is sent, it includes a transition from the DATA line to the low level during the high period of the SCK line.

· Stop signal

When the transmission is terminated and data transmission is stopped, it includes a transition from the DATA line to a high level during the high period of the SCK line.

HTU21D and SHT21 have the same command list:

Both HTU21D and SHT21 actually use four pins, power and ground, and two ports for I2C communication. The output is digital: 14-bit temperature value and 12-bit humidity value can also be modified to 12-bit temperature and 8-bit humidity through the user register.

Therefore, HTU21D is fully compatible with SHT20 and SHT21 software protocols and can be replaced with each other.

6. Actual measurement effect display of HTU21D temperature and humidity sensor:

1) Use Shenzhen New World Technology Co., Ltd. (Apollo) to provide a four-in-one temperature and humidity demo Demo for testing, and use the host computer software to implement data recording:

Four in one temperature and humidity demo

PC recording software

As can be seen from the above figure, the consistency of the four HTU21D products is very good. It can also be seen from the graph that the recorded data curve has been flat, indicating that the HTU21D has good stability.

2) Use the self-made HTU21 with board and 1602LCD display to compare with the high-precision handheld watch data.

In order to facilitate customer testing and use, the manufacturer introduced the HTU21PCBA which has been soldered with a small PCB board:

HTU21PCBA with board and 1602LCD display, compared with high-precision handheld table data:

Summary: HTU21D is fully compatible with SHT20 and SHT21. Pin to Pin can be implemented on hardware pins without modifying the circuit board. The software program is also basically the same, and the two can be replaced compatible without any modification. From the manufacturer's quotation, HTU21D has more advantages than SHT20 and SHT21, and it is a good choice for manufacturers to reduce production costs.

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