Product Manual

Product Specification Book

• Product Specification Book

  Product Name:	Digital temperature and humidity sensor
  Product model:	MHTRD11
  Formulator:	He Genwen
  Reviewer:	Yuan Chao
  time:	2023-04- 17

   

  

  Modify the record table:

   

   

   

  Version	Change content	Change people	Change date
  V1.0	New	He Genwen	2020-4-24

   

  1. Product Overview

  Digital temperature and humidity sensors refer to devices or devices that can simultaneously collect and convert temperature and humidity into digital electrical signals.

  MHTRD11   Digital temperature and humidity sensors are simply called temperature and humidity sensors.It is a temperature and humidity composite sensor containing calibrated digital signal output. This product has high reliability and excellent long-term stability.

  If there is no special explanation in the following content, the "temperature and humidity sensor" in the article is this " MHTRD11”  product.

   

  2. Product Features

   

  Reasonable cost, long-term stability, with relative humidity and temperature measurement, ultra-fast response, strong anti-interference ability, ultra-long signal transmission distance, single-bus digital signal output, accurate calibration, excellent quality.

  3. Product appearance

   

  

  Figure 1 Product size diagram  (unit: mm )

   

  Pin number	name	Function	Connection method
  1	VDD	3.3~5.5V     DC	Power supply positive pole
  2	DATA	one-wi re  Serial data	Single data bus
  3	NC	none	Empty pin
  4	GND	Signal ground	Negative power supply

  Pin Description Table

   

  IV. Application Scope

   

  It is used in HVAC, dehumidifiers, agriculture, cold chain warehousing, testing and testing equipment, consumer goods, automatic control, data recorders, weather stations, household appliances, humidity regulators, medical care, vehicles, ship transportation and other related fields that require detection and control of temperature and humidity.

  V. Product parameters

   

  1 Electrical characteristics

   

  Electrical Characteristics Parameter Table

   

   

  parameter	condition	min	Type	max	Unit
  Power supply voltage		3.3	5.0	5.5	V
  Power supply current		0.06(Standby )	-	1.0(Measurement )	mA
  Sampling cycle	Measurement		>2		S/Second-rate

   

   

  2 Relative humidity

   

  Relative humidity measurement performance parameter table

   

   

  parameter	condition	min	type	max	Unit
  Range range		20		95	%RH
  Accuracy [1]	25℃		±3		%RH
  Repeatability			±1		%RH
  Interchangeability	Completely interchangeable
  Response time [2]	1/e(60%)		<10		S
  Hysteresis			±0.5		%RH
  drift [3]	Typical values		<±0.5		%RH/Year

   

   

  3 temperature

   

  Temperature measurement performance parameter table

   

   

  parameter	condition	min	type	max	Unit
  Range range		-20		60	℃
  Accuracy [1]	25℃		±1		℃
  Repeatability			±0.5		℃
  Interchangeability	Completely interchangeable
  Response time [2]	1/e(60%)		<10		S
  Hysteresis			±0.3		℃
  drift [3]	Typical values		<±0.5		℃/Year

   

  Note [1]This accuracy is when the sensor is tested at 25 ℃and 5 V， The accuracy index tested under conditions does not include hysteresis and nonlinearity, and is only suitable for non-condensing environments.Note [2]At 25 ℃and 1 m/s  Under the conditions of airflow, the time required to achieve 60% of the first-order response.

  Note [3]The values may be higher in volatile organic mixtures.See the application storage information in the manual.

   

   

  VI. Typical Applications

   

  

  Typical application circuit diagram of temperature and humidity sensor

   

  The connection between the microprocessor and the temperature and humidity sensor and the typical application circuit are shown in the figure above.  DATA  After the pin is connected through the signal line, it is connected to the microprocessor after passing through the pull-up resistor. I/O   Connect to the port.

  In circuit design and application, the following matters need to be paid attention to:

  1 、Shielded cables are recommended for signal cables to obtain ideal signal quality and appropriate transmission distance.

  2 、Recommended: Use 4.7 when the length of the connection signal cable is shorter than 5 meters. KΩThe pull-up resistor, the wire length is greater than 5 m  When the resistance value of this resistance is reduced according to the actual situation.

  3 、Use 3.3 V    When powering through voltage, the signal connection line should be as short as possible. Too long the signal connection line will lead to insufficient power supply of the sensor, causing measurement deviation or failure.

  4、The temperature and humidity values read out each time are the result of the last measurement.To obtain real-time data, it is necessary to read 2 consecutive times, but it is not recommended to read the sensor more consecutive times.Accurate data can be obtained by reading sensors more than 2 seconds each time.

  5 、If there is fluctuation in the power supply part, it will affect the temperature measurement value.If the ripple of the switch power supply is too large, the temperature will jump, and filtering measures should be taken at this time.

  7. Serial communication data format description  (Single-line bidirectional  O n e -W ire )

   

  ◎Single bus description

  The single-bus temperature and humidity sensor device adopts a simplified single-bus communication method.A single bus means only one data cable.Data exchange and control in the system are all completed by a single bus.equipment  (Host or slave ) Connect to the data line via an open drain or tri-state port to allow the device to release the bus when it does not send data, allowing other devices to use the bus;Single bus usually requires an external pull-up resistor  (Commonly used 4.7 k Ω ) ，In this way, when the bus is idle, its state is high.Since the single bus system is a master-slave structure  (Master machine structure ) ，The slave can only answer when the host calls the slave, so the host access devices must strictly follow a single bus sequence. If sequence disorder occurs, the sensor device as the slave will not respond to the host's call.

  ◎Single bus transmission data bit definition

  DATA  The wire is used for communication and synchronization between the host and the temperature and humidity sensor. It adopts a single bus data format, transmits 40 bits of data at a time, and exits first with a high bit.Data format:

  8bit   Humidity integer bit data + 8bit   Humidity decimal places data + 8bit   Temperature integer bit data + 8bit   Temperature decimal data + 8bit   Check bit.

   

  ◎Check digit data definition

  “8bit   Humidity integer data + 8bit   Humidity decimal data + 8bit   Temperature integer data + 8bit   Temperature decimal data”, bit length is 8 bit  。  The check bit is equal to the last 8 digits of the result.

   

   

  name	Single bus data format definition
  Start signal	Microprocessor transfers data bus  (SDA) Lower for a period of time at least 18 ms (The maximum must not exceed 30 ms) ，Notify the sensor to prepare data.
  Response signal	Sensor transfers the data bus  (SDA) Pull down 83 µs， Receive high 87 µs  In response to the start signal of the host.
  Data format	After receiving the host start signal, the sensor will be sent from the data bus at one time.  (SDA) Serial output 40 bits of data, high bits are first released.
  Wetness	The humidity level is the humidity integer part data, and the humidity level is the humidity fractional part data.
  temperature	The temperature high is the integer part of the temperature, and the temperature low is the fractional part of the temperature. Define the temperature low  bit8  When it is 1, it means negative temperature and the temperature is low. bit8  When it is 0, it indicates positive temperature.
  Check bit	Check bit ＝High humidity level +Low humidity +High temperature +The temperature is low.

  Single bus transmission data signal specification format table

   

  Example 1: The 40 bits of data received are as follows:

   

  0011 1010	0000 0101	0001 0111	0000 0110	0101 1100
  High humidity of 8 (Integer )	Low humidity 8 digits (Decimals )	Temperature 8 positions (Integer )	Low temperature 8 digits (Decimals )	Check bit

  Calculation of check bit: 0011 1010 +0000 0101+0001 0111+0000 0110= 0101 1100，

  If the calculated check bit value is 0101 0001 and the received check bit value 0101 0001, the received data is correct.The analysis is as follows:

  Humidity value: 0011 1010 (Integer )=3AH=58% RH       0000 0101(Decimals )=05H=0.5% RH

  =>Humidity value is: 58% RH + 0.5% RH = 58.5%RH

  Temperature value: 0001 0111 (Integer )=17H=23℃ 0000 0110(Decimals )=06H=0.6℃

  =>Temperature value is 23 ℃ + 0.6℃ = 23.6℃

   

  ◎Special Instructions:

  When the temperature is lower than 0 ℃ The first bit of the lower 8 bits of the temperature data (That is the highest position )Set to 1.Example: - 12.3 ℃ Expressed as 0000 1100 1000 0011

  Temperature value: 0000 1100 (Integer )=0CH=12℃ ，1000 0011(Decimals )=03H＝0.3℃ ，1  Represents the temperature is below zero

  =>The temperature value is - (12℃+0.3℃)＝ - 12.3℃

   

  Example 2: The 40 bits of data received are as follows:

   

  0011 1010	0000 0101	0001 0111	0000 0110	0101 1101
  High humidity of 8 (Integer )	Low humidity 8 digits (Decimals )	Temperature 8 positions (Integer )	Low temperature 8 digits (Decimals )	Check bit

  Calculation of check bit: 0011 1010 +0000 0101+0001 0111+0000 0110＝ 0101 1100

  Because the calculated check bit value is 0101 1100 and the received check bit value 0101 1101, the data received this time is incorrect, the data will be discarded and the data needs to be resent and received.

  ◎Data timing chart

  User Host  (microprocessor  MCU) After sending a start signal, the slave /Sub-machine  (Temperature and humidity sensor  Sensor) Switch from low power mode to high speed mode, after the host start signal is finished, the sensor sends a response signal and sends 40 bit   and trigger a signal acquisition.The signal transmission timing is shown in the figure.

  

  Data timing chart Note: The temperature and humidity data read by the host from the sensor is always the previous measurement value. If the interval between the two measurements is very long, please read the data twice in a row and discard the first data, and use the measured value obtained the second time as the real-time temperature and humidity value.

  ◎Peripheral reading steps

  Communication between the master and slave can be completed through the following steps [microprocessor]  MCU (Such as peripherals ) Read the sensor  Sensor  Steps of data】.Step 1: After the temperature and humidity sensor is powered on (After the temperature and humidity sensor is powered on, wait for 1 second to pass the unstable state, and no commands can be sent during this period. )， Test the ambient temperature and humidity data and record the data in the sensor.At the same time, the temperature and humidity sensor  DATA   The data line is pulled up by the pull-up resistor and remains at a high level. At this time, the temperature and humidity sensor is DATA   The pin is in the input state, detects external signals at all times, and waits for a call from the host.

  Step 2: Microprocessor  (Host ) of  I/O   Set to output and output low level at the same time, and the low level hold time cannot be less than 18 ms  (The maximum shall not exceed 30 ms) ，Then the microprocessor  I/O   Set to input status.Because the pull-up resistor pulls up the level, the microprocessor's I/O   That is, the temperature and humidity sensor DATA  The data line also becomes higher, waiting for the temperature and humidity sensor to answer the signal, and the sending signal is shown in the figure:

  

  Step 3:

  Temperature and humidity sensor  (From the machine /Sub-machine ) of  DATA   When the pin detects that the external signal has a low level, wait for the external signal to end. After pulling high waiting delay timing, the temperature and humidity sensor will be DATA   The pin is in the output state, outputting a low level of 83 microseconds as the response signal, followed by a high level of 87 microseconds notifying the peripheral to prepare for receiving data.Meanwhile, the microprocessor I/O   In input state, detected I/O   There is a low level (Temperature and humidity sensor 83 microsecond response signal ) After that, wait for the data to be received at 87 microseconds for high level, and the sending signal is shown in the figure:

  sensor  (From the machine /Sub-machine ) Response signal diagram

   

  Step 4:

  By temperature and humidity sensor  DATA   The pin outputs 40 bits of data, the microprocessor is based on I/O    The change in level receives 40 bits of data, and the format of bit data "0" is: 54 microseconds low level and 23-27 microseconds high level,

  The format of bit data "1" is: 54 microseconds low level plus 68-74 microseconds high level.

  The signal format of bit data "0" and "1" information is shown in the figure:

   

  End signal:

  Temperature and humidity sensor  DATA   After the pin outputs 40 bits of data, continue to output low level for 54 microseconds and then switch to input state. Because the pull-up resistor pulls up, DATA  The line then becomes a constant high level, releasing the bus.

  At this time, the temperature and humidity sensor retests the ambient temperature and humidity data, and records and stores data, waiting for the arrival of external signals.

   

  Note: In order to ensure accurate communication of the sensor, when users read the signal, please strictly follow the parameters and timing in the table below and the data timing chart.

   

  symbol	parameter	min	type	max	unit
  Tbe	The host start signal is pulled down time	18	20	30	ms
  Tgo	Host release bus time	10	13	35	S
  Trel	Response low level time	78	83	88	S
  Treh	Response to high level time	80	87	92	S
  TLOW	Signal "0" and "1" low level time	50	54	58	S
  T H0	Signal "0" high level time	23	24	27	S
  T H1	Signal "1" high level time	68	71	74	S
  en	Sensor release bus time	52	54	56	S

   

  8. Application information

   

  1 、Working and storage conditions

  Exceeding recommended work ranges can result in up to 3% RH  temporary drift signal.After returning to the normal working bar, the sensor slowly returns to the calibration state.To speed up the recovery process, see the next section “Recovery Processing”.

   

  environment	temperature  (℃)	humidity  (RH)
  Working environment	-20~60	5%~95%
  Storage environment	-20~60  (Suggestions 10 ~30)	5%~95%  (Recommended 40 ~70%)

  Long-term use under abnormal working conditions will accelerate the aging process of the product.

  Avoid placing the components in condensation and overdry environments and the following environments for a long time.

  A 、 Salt spray;                           B 、 Acid or oxidizing gases, such as sulfur dioxide, hydrochloric acid;

   

  2 、Recovery processing

  The sensor placed under extreme operating conditions or in chemical steam can be restored to its calibration state by the following processing procedure.

  Handler: at 45 ℃ and<10%rh 2="" 20="" keep="" it="" under="" humidity="" for="" hours="" constant="" temperature="" drying="" then="" at="" and="">70%RH   Keep it under humidity conditions for more than 5 hours.

  3 、Temperature influence

  The relative humidity of the gas depends to a large extent on temperature.Therefore, when measuring humidity, the humidity sensor should be ensured to operate at the same temperature as much as possible.If you share a printed circuit board with the electronic components that release heat, the sensor should be kept as far away from the electronic components that generate heat as much as possible and installed under the heat source while maintaining good ventilation of the housing.To reduce heat conduction, the sensor pins should minimize metal connections. The contact area of the sensor pad and the copper, tin, gold and other metal coatings of other parts of the printed circuit board should be as small as possible or the distance should be as large as possible, and a gap should be left between the two.

  4 、Light effects

  Long-term exposure to sunlight or strong ultraviolet radiation will reduce performance.

   

  5 、Effects of exposure to chemicals

  The inductive layer of the resistive humidity sensor will be disturbed by chemical vapors, and the diffusion of chemical substances in the inductive layer may cause measurement value drift and sensitivity to decrease.In a pure environment, pollutants will be released slowly.The recovery process described above can speed up the implementation of this process.

  High concentrations of chemical contamination can lead to complete damage to the sensor sensing layer, thus causing the sensor to fail.

   

  6 、Wiring precautions

  The quality of the signal wire will affect the communication distance and communication signal quality, and it is recommended to use high-quality shielded wires.

   

  7 、Things to note

  Let manual welding, up to 300 ℃The contact time must be less than 3 seconds under temperature conditions.

  Let the wave soldering temperature not exceed 260 degrees Celsius, and the time must be less than 5 seconds.

  Orders: It is prohibited to use alcohol, washing water or other liquids to clean the device body or soak it into the liquid.

   

  9. Key Notice

   

  Copyright, Shenzhen Yuanjian Sensing Technology Co., Ltd. ®All rights reserved.

  No unit or individual may excerpt or copy part or all of the contents of this manual without the written consent of the company, and shall not be disseminated in any form.

   

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  The trademarks, other trademarks, product names, service names and company names appearing in the documents and products described in this manual are owned by their respective owners.Without authorization or permission, you agree not to use the above trademarks in part or in whole in any activity, product or service that does not belong to us, nor to use the above trademarks in a manner that confuses, misleads or deceptive, or may derogate us or our information, projects or development results.

  Disclaimer:

  The products, services or features you purchase shall be subject to the commercial contract and terms of Shenzhen Yuanjian Sensing Technology Co., Ltd., and all or some of the products, services or features described in this document may not be within your purchase or use.Unless otherwise agreed in the contract, the Company makes no representations or warranties, express or implied, regarding the contents of this document.Due to product version upgrades or other reasons, the content of this document will be updated from time to time.Unless otherwise agreed, this document is intended for use only and all statements, information and suggestions in this document do not constitute any warranty, express or implied.Although the company tries to avoid errors in the writing process and translation of this article, there may be textual errors due to editing or printing reasons, and we shall not be responsible for any problems caused by this.The above specifications and test data are based on samples as the test objects, and the actual product data has discrete deviations.The company reserves the right to change the product technical parameters without notice within the scope of the law. Please refer to the actual product.

  If you have any unclear or need to confirm, please contact us!