Sensirion SHT3x Digital Temperature and Humidity Sensor User Guide

Sensirion SHT3x Digital Temperature and Humidity Sensor

Product Information

Specifications

• Sensor Models: SHT3x, SHT4x
• Accuracy: Improved for both SHT3x and SHT4x
• Power Consumption: Reduced in SHT4x compared to SHT3x
• Heater: Powerful internal heater for self-decontamination in SHT4x
• Versatility: Superior technology and versatility from two decades of sensor development
• Communication Interface: SHT3x – 8 pins I2C, 2 Addresses; SHT4x – 4 pins I2C, multiple addresses

Product Usage Instructions

General Guideline
This document guides replacing SHT3x with sensors from the SHT4x family. It outlines important differences to consider during the design-in processes.

Performance Comparison

Relative Humidity and Temperature

Relative Humidity (RH):
Accuracy, repeatability, resolution, hysteresis, specified range, response time, long-term drift, and condensation behaviour differ between SHT3x and SHT4x.

Temperature:
Accuracy, repeatability, resolution, specified range, response time, and long-term drift values vary between the two sensor models.

Specifications

• Sensor Models: SHT3x, SHT4x
• Accuracy: Improved for both SHT3x and SHT4x
• Power Consumption: Reduced in SHT4x compared to SHT3x
• Heater: Powerful internal heater for self-decontamination in SHT4x
• Versatility: Superior technology and versatility from two decades of sensor development
• Communication Interface: SHT3x – 8 pins I2C, 2 Addresses; SHT4x – 4 pins I2C, multiple addresses

Frequently Asked Questions (FAQ)

• Q: Where can I find further information about the sensors?
  A: For additional details and resources, visit www.sensirion.com or refer to the Further Information section in the user manual.

SHT3x – SHT4x Transition Guide
Boarding the new flagship RH/T sensor generation

• Improved accuracy, power consumption, and robustness
• Powerful internal heater for self-decontamination
• Superior versatility and technology from two decades of sensor development

Abstract

Introduced as a highly versatile digital humidity (RH) and temperature (T) sensor platform, the SHT3x family already enabled outstanding sensing performance for several years. Sensirion now proudly features its all-new flagship sensors from the SHT4x family, which profit from about two decades of RH/T sensor development. Dedicated to best-in-class performance, low power consumption, smallest footprint, and attractive pricing, our new SHT4x sensors are the products of choice for many SHT3x applications. In particular, the SHT4x outperforms the SHT3x in every aspect and offers versatile add-ons, such as a powerful heater for self-decontamination, conformal coating protection, or filter membranes.

Important changes

with D T ³60°C, Full condensation robustness

General

This document aims to provide a high-level guideline to replace SHT3x with sensors from the SHT4x family and outlines important differences to be considered in design-in processes.

Performance Comparison

Relative Humidity and Temperature

Relative humidity
RH accuracy1| Typ.| ± 2| ± 1.0 … 1.8| %RH
Repeatability2| –| 0.08/0.15/0.21| 0.08/0.15/0.25| %RH
Resolution3| –| 0.01| 0.01| %RH
Hysteresis| –| ±0.8| ±1| %RH
Specified range4| extended5| 0 – 100| 0 – 100| %RH
Response time6| t 63%| 8| 4| s
Long-term drift7| Typ.| <0.25| <0.25| %RH/y
Condensation behavior| Droplet formation| Slight signal drop| No signal drop| –
Temperature
T Accuracy1| Typ.| ± 0.2| ± 0.1| °C
Repeatability2| –| 0.04/0.08/0.15| 0.04/0.07/0.1| °C
Resolution3| –| 0.01| 0.01| °C
Specified range4| –| −40 – +125| −40 – +125| °C
Response time8| t 63%| > 2| 2| s
Long-term drift9| Typ.| < 0.03| < 0.03| °C/y

Table 1.
Humidity and temperature specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

1. For definition of typ. accuracy, please refer to the document “Sensirion Humidity Sensor Specification Statement”.

2. The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurement values at constant conditions and is a measure for the noise on the physical sensor output. Different repeatability commands are listed in Table 5.

3. Resolution of A/D converter.

4. Specified range refers to the range for which the humidity or temperature sensor specification is guaranteed.

5. For details about the recommended humidity and temperature operating range, please refer to the SHT4x Datasheet.

6. Time for achieving 63% of a humidity step function, valid at 25°C and 1 m/s airflow. Humidity response time in the application depends on the design of the
   sensor.

7. Typical value for operation in normal RH/T operating range. Max. value is < 0.5 %RH/y. The value may be higher in environments with vaporized solvents, out-gassing
   tapes, adhesives, packaging materials, etc. For more details, please refer to Handling Instructions.

8. Temperature response time depends on the heat conductivity of the sensor substrate and design-in of the sensor in the application.

9. Max. value is < 0.04°C/y. The long-term drift for SHT43 is < 0.01 C/y.

Electrical Characteristics

Parameter| Symbol| Conditions| SHT3x| SHT4x| Units
---|---|---|---|---|---
Min| Typ.| Max| Min| Typ.| Max
Supply voltage| V DD|  | 2.15| 3.3| 5.5| 1.08| 3.3| 3.6| V
Power-up/down level| VAPOUR| Static power supply| 1.8| 2.1| 2.15| 0.6| –| 1.08| V

Supply current (heater not activated)10

| ****

ADD

| Idle state| –| 0.2| 2.0| –| 0.08| –| µA
Measurement| –| 600| 1500| –| 320| –| µA
Average| –| 1.7|  | –| 0.4 (low)

2.2 (high)

| –| µA
Power consumption11| –| Average| –| 5.6|  | –| 0.5 (low)

2.6 (high)

| –| µW
Low-level input voltage| V IL| –| 0| –| 0.3 V DD| 0| –| 0.3 V DD| V
High-level input voltage| VIA| –| 0.7 V DD| –| V DD| 0.7 V DD| –| V DD| V
Application circuit design| –| –| Similarly, for details the see SHT3x or SHT4x datasheet| –

Table 2.
Key electrical specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Timing Specifications

Parameter| Symbol| Conditions| SHT3x| SHT4x| Units
---|---|---|---|---|---
Min| Typ.| Max| Min| Typ.| Max
Power-up time| t PU| After a hard reset,

V DD ≥ V POR

| –| 0.5| 1| –| –| 1| ms
Soft reset time| t SR| After soft reset| –| 0.5| 1| –| –| 1| ms
Measurement duration| teas| Medium repeatability| –| 4.5| 6| –| 3.7| 4.5| ms
Heater-on duration| t Heater|  | –| –| –| 0.1| –| 1| s

Table 3. Key timing specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Flagship SHT4x Feature: Built-In Heater

The SHT4 sensor incorporates a powerful on-chip heater, which can be used for self-decontamination, e.g. in environments with solvents present, and periodical creep compensation in prolonged application in the highest humidity. It provides an over-temperature of about 60 °C and can be switched on by the command specified in Table 5, after which the heater will run for 0.1 or 1 second. After the heater is time, a temperature and humidity measurement is started and the heater will be automatically turned off after the measurement is finished. This safety feature prevents permanent turn-on of the heater. There is no dedicated command to turn off the heater since it has an internal timer set to 1s after which it is switched off automatically. If higher heating temperatures than achievable in 1 second are desired, consecutive heating commands need to be sent to the sensor.

1. SHT4x values for 1.2 V supply voltage
2. SHT4x values for 1.2 V supply voltage

Package Design Differences

The SHT4x comes in a new open-cavity dual flat no-lead (DFN) package design to enable additional features, such as conformal coating, protection cover, and filter membrane compatibility. In comparison to the SHT3x, the package is considerably smaller, enabling power-efficient, accurate, and robust RH/T sensing with fast reaction times. Instead of featuring eight pins, the bottom side of the SHT4x DFN package exposes four metallic contacts, which are Ni/Pd/Au coated.

Protection compatibility

|

–

| Compatible with conformal coating,

Compatible with filter membranes

| Compatible with conformal coating,

Compatible with filter membranes

|
Pin Layout| –| 2 x 4 pins| 2 x 2 pins|
Necessity for fine-print PCB| –| no| no|
Pin Assignment| –| | SDA

SCL

| | VSS

VDD

| Drawings not to scale VDD: Supply voltage SCL: Serial clock

SDA: Serial data bidirectional VSS: Ground

Pin Size| mm| 0.25 x 0.35| 0.3 x 0.3|
Pin Pitch| mm| 0.5| 0.8|
Pin Material| –| Ni/Pd/Au coated Cu| Ni/Pd/Au coated Cu|
Housing Material| –| Epoxy housing| Epoxy housing|

Table 4. Key package differences between the SHT3x and SHT4x. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Figure 1. Dimensional drawing of the SHT3x including (units mm).

Communication Compatibility

Both chips feature the I2C communication protocol and alternative addresses for high flexibility in all applications. Addressing a specific SHT4x sensor is done by sending its 7-bit I2C address followed by an eighth bit, denoting the communication direction: “Zero” indicates transmission to the sensor, i.e. “write”, a “one” indicates a “read” request. In addition, the SHT4x features different measurement options for different precision needs and a heater option, as detailed in Table 5 and Section 3.

Command|

Description

---|---
BIN| HEX
1111 1101| FD| Measure T & RH with the highest precision (high repeatability)
1111 0110| F6| Measure T & RH with medium precision (medium repeatability)
1110 0000| E0| Measure T & RH with the lowest precision (low repeatability)
1000 1001| 89| Read serial
1001 0100| 94| Soft Reset
0011 1001| 39| Activate highest heater power for 1s

• Table 5. Overview of I2C commands for the SHT4x.
• For further details on the I2C communication, such as general protocol description, data types and lengths, and checksum calculation, kindly refer to the SHT4x datasheet.

Quality and Material Contents

Qualification of the SHT3x and SHT4x is performed based on the JEDEC JESD47 qualification test method. While both devices are fully RoHS and REACH compliant, the SHT4x is also WEEE compliant.

Further Information

This transition guide aims to provide an overview of the key differences between the SHT3x and the SHT4x, yet might not be fully inclusive. For further reading on the SHT4x specifications, communication, operation, and application, please consult the dedicated SHT3x and SHT4x documents provided on the Sensirion webpage www.sensirion.com. In case you need specific details, or would like to request assistance in transitioning from the SHT3x to the SHT4x or any other Sensirion product, please consult us directly at www.sensirion.com/en/about-us/contact/.

Revision History

Important Notices

Warning, Personal Injury
Do not use this product as a safety or emergency stop device or in any other application where failure of the product could result in personal injury. Do not use this product for applications other than its intended and authorized use. Before installing, handling, using or servicing this product, please consult the datasheet and application notes. Failure to comply with these instructions could result in death or serious injury.

If the Buyer shall purchase or use SENSIRION products for any unintended or unauthorized application, the Buyer shall defend, indemnify and hold harmless SENSIRION and its officers, employees, subsidiaries, affiliates and distributors against all claims, costs, damages and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if SENSIRION shall be allegedly negligent concerning the design or the manufacture of the product.

ESD Precautions
The inherent design of this component causes it to be sensitive to electrostatic discharge (ESD). To prevent ESD-induced damage and/or degradation, take customary and statutory ESD precautions when handling this product.
See application note “ESD, Latchup and EMC” for more information.

Warranty
SENSIRION warrants solely to the original purchaser of this product for 12 months (one year) from the date of delivery that this product shall be of the quality, material and workmanship defined in SENSIRION’s published specifications of the product. Within such period, if proven to be defective, SENSIRION shall repair and/or replace this product, in SENSIRION’s discretion, free of charge to the Buyer, provided that:

• notice in writing describing the defects shall be given to SENSIRION within fourteen (14) days after their appearance;
• such defects shall be found, to SENSIRION’s reasonable satisfaction, to have arisen from SENSIRION’s faulty design, material, or workmanship;
• the defective product shall be returned to SENSIRION’s factory at the Buyer’s expense; and
• the warranty period for any repaired or replaced product shall be limited to the unexpired portion of the original period.

This warranty does not apply to any equipment that has not been installed and used within the specifications recommended by SENSIRION for the intended and proper use of the equipment. EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS OR IMPLIED, CONCERNING THE PRODUCT. ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.

SENSIRION is only liable for defects of this product arising under the conditions of operation provided for in the data sheet and proper use of the goods. SENSIRION explicitly disclaims all warranties, express or implied, for any period during which the goods are operated or stored not by the technical specifications.
SENSIRION does not assume any liability arising out of any application or use of any product or circuit and specifically disclaims any liability, including without limitation consequential or incidental damages. All operating parameters, including without limitation recommended parameters, must be validated for each customer’s applications by the customer’s technical experts. Recommended parameters can and do vary in different applications.
SENSIRION reserves the right, without further notice, (i) to change the product specifications and/or the information in this document and (ii) to improve the reliability, functions and design of this product.
Copyright © 2021, by SENSIRION. CMOSens® is a trademark of Sensirion. All rights reserved

Headquarters and Subsidiaries

• Sensirion AG Laubisruetistr. 50 CH-8712 Staefa ZH Switzerland
• phone: +41 44 306 40 00
• Fax: +41 44 306 40 30
• info@sensirion.com
• www.sensirion.com
• Sensirion Taiwan Co. Ltd
• phone: +886 3 5506701
• info@sensirion.com
• www.sensirion.com.

To find your local representative, please visit www.sensirion.com/distributors.

References

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