Product manual

SPECIFICATION

• SPECIFICATION

  product name：	Digital temperature and humidity sensor
  Model：	MHTRD11
  Creator：	He Genwen
  reviewed by：	Yuan Chao
  time：	2023-04- 17

   

  

  Modify Record Table：

   

   

   

  version	change content	Changed by	change date
  V1.0	new-built	He Genwen	2020-4-24

   

  1、Overview

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

  The MHTRD11 digital temperature and humidity sensor is abbreviated as a temperature and humidity sensor. It is a temperature and humidity composite sensor with calibrated digital signal output. This product has high reliability and excellent long-term stability.

  Unless otherwise specified, the "temperature and humidity sensor" mentioned in the text refers to the "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, precise calibration, and excellent quality.

  3、Appearance

   

  

  Figure 1 Product dimension diagram (unit: mm)

   

  Pin number	name	function	Connection method
  1	VDD	3.3~5.5V     DC	Positive pole of power supply
  2	DATA	one-wi re serial data	Single data bus
  3	NC	not have	Empty pin
  4	GND	signal ground	Negative pole of power supply

  Pin Description Table

   

  4、Application scope

   

  Used in fields such as HVAC, dehumidifiers, agriculture, cold chain storage, testing and testing equipment, consumer goods, automatic control, data recorders, weather stations, household appliances, humidity regulators, medical equipment, vehicles, ships, and other related fields that require temperature and humidity detection and control.

  5、Product parameters

   

  1 Electrical characteristics

   

  Electrical characteristic parameter table

   

   

  parameter	condition	min	Type	max	Unit
  Supply Voltage		3.3	5.0	5.5	V
  Power supply current		0.06(Standby)	-	1.0(measure)	mA
  sampling period	measure		>2		S/order

   

   

  2 relative humidity

   

  Performance parameter table for relative humidity measurement

   

   

  parameter	condition	min	type	max	Unit
  Range range		20		95	%RH
  accuracy[1]	25℃		±3		%RH
  repeatability			±1		%RH
  interchangeability	Complete Interchange
  response time[2]	1/e(60%)		<10		S
  Hysteresis			±0.5		%RH
  drift[3]	Typical value		<±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	Complete Interchange
  response time[2]	1/e(60%)		<10		S
  Hysteresis			±0.3		℃
  drift[3]	Typical value		<±0.5		℃/year

   

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

  Note [3]: In volatile organic mixtures, the values may be higher. See the application storage information in the manual。

   

   

  6、Typical applications

   

  

  Typical application circuit diagram of temperature and humidity sensors

   

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

  In circuit design and application, the following precautions should be taken：

  
  

   

• 1. It is recommended to use shielded wires for signal cables to achieve ideal signal quality and appropriate transmission distance.

• 2. Suggestion: When the length of the connecting signal cable is less than 5 meters, use a 4.7K Ω pull-up resistor. When the line length is greater than 5 meters, reduce the resistance value of this resistor according to the actual situation.

• 3. When using a 3.3V voltage supply, the signal connection line should be as short as possible. A signal connection line that is too long can cause insufficient power supply to the sensor, leading to measurement deviation or failure.

• 4. The temperature and humidity values read each time are the results of the previous measurement. To obtain real-time data, it is necessary to read it twice in a row, but it is not recommended to read the sensor more times in a row. Accurate data can be obtained by reading the sensor every time with an interval greater than 2 seconds.

• 5. If there is any fluctuation in the power supply, 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 specification (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 there is only one data cable. The data exchange and control in the system are all completed by a single bus. The device (host or slave) is connected to the data line through a drain open circuit or three-state port, allowing the device to release the bus and allow other devices to use the bus when not sending data; A single bus usually requires an external pull-up resistor (usually 4.7k Ω), so that when the bus is idle, its state is high. Due to the fact that a single bus system is a master-slave structure (master-slave structure), the slave can only respond when the host calls the slave. Therefore, the host must strictly follow the single bus sequence when accessing the device. If the sequence is chaotic, the sensor device as the slave will not respond to the host's call.

• Definition of data bits for single bus transmission

• The DATA cable is used for communication and synchronization between the host and temperature and humidity sensors. It adopts a single bus data format and transmits 40 bits of data at once, with high bits first out. Data format:

• 8-bit humidity integer data+8-bit humidity decimal data+8-bit temperature integer data+8-bit temperature decimal data+8-bit checksum.

• ◎ Definition of Check Bit Data

• "8-bit humidity integer data+8-bit humidity decimal data+8-bit temperature integer data+8-bit temperature decimal data", with a bit length of 8 bits. The check digit is equal to the last 8 digits of the obtained result.

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• name	Single bus data format definition
  Start signal	The microprocessor lowers the data bus (SDA) for at least 18ms (maximum not exceeding 30ms) and notifies the sensor to prepare data.
  response signal	The sensor lowers the data bus (SDA) by 83 µ s and then increases it by 87 µ s in response to the host's initial signal.
  data format	After receiving the host start signal, the sensor outputs 40 bits of data in series from the data bus (SDA) at once, with high bits being first out.
  Humidity	The high humidity represents the integer part of the humidity data, while the low humidity represents the decimal part of the humidity data.
  Temperature	The high temperature represents the integer part of the temperature data, while the low temperature represents the decimal part of the temperature data, When the low bit 8 of the temperature is defined as 1, it represents negative temperature, and when the low bit 8 of the temperature is defined as 0, it represents positive temperature.
  check bit	Check bit=high humidity+low humidity+high temperature+low temperature.

• Single bus transmission data signal specification format table

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• Example 1: The received 40 bit data is as follows：

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• 0011 1010	0000 0101	0001 0111	0000 0110	0101 1100
  Humidity up to 8 digits (integer)	Low humidity to 8 decimal places	Temperature up to 8 digits (integer)	Low temperature to 8 decimal places	check bit

• Check digit calculation：0011 1010+0000 0101+0001 0111+0000 0110= 0101 1100，

• If the calculated checksum value is 0101 0001 and the received checksum value is equal to 0101 0001, then the received data is correct. The analysis is as follows:

• Humidity value: 0011 1010 (integer)=3AH=58% RH 0000 0101 (decimal)=05H=0.5% RH

• =>The humidity value is: 58% RH+0.5% RH=58.5% RH

• Temperature value: 0001 0111 (integer)=17H=23 ℃ 0000 0110 (decimal)=06H=0.6 ℃

• =>The temperature value is 23 ℃+0.6 ℃=23.6 ℃

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• ◎Special Instructions：

• When the temperature is below 0 ℃, the first (highest) digit of the low 8 bits of the temperature data is set to 1. Example: -12.3 ℃ represents 0000 1100 1000 0011

• Temperature value: 0000 1100 (integer)=0CH=12 ℃, 1000 0011 (decimal)=03H=0.3 ℃, where 1 represents the temperature below zero

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

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• Example 2: The received 40 bit data is as follows：

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• 0011 1010	0000 0101	0001 0111	0000 0110	0101 1101
  Humidity up to 8 digits (integer)	Low humidity to 8 decimal places	Temperature up to 8 digits (integer)	Low temperature to 8 decimal places	check bit

• Check digit calculation: 0011 1010+0000 0101+0001 0111+0000 0110=0101 1100

• Because the calculated checksum value of 0101 1100 is not equal to the received checksum value of 0101 1101, the received data is incorrect and will be discarded. The data needs to be resent and received again.

• ◎ Data timing chart

• After the user's host (microprocessor MCU) sends a start signal, the slave/slave (temperature and humidity sensor) switches from low-power mode to high-speed mode. After the host's start signal ends, the sensor sends a response signal, sends out a 40bit data, and triggers 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 there is a long interval between two measurements, please read the data twice in a row and discard the first data. The real-time temperature and humidity value obtained from the second measurement is used.

• ◎ External device reading steps

• The communication between the host and the slave can be completed through the following steps: the microprocessor MCU (such as peripheral devices) reads data from the sensor. Step 1: After the temperature and humidity sensor is powered on (the temperature and humidity sensor needs to wait for 1 second to bypass the unstable state, during which no commands can be sent), test the environmental temperature and humidity data, and record the data in the sensor. At the same time, the DATA data cable of the temperature and humidity sensor is pulled high by the pull-up resistor and remains at a high level. At this time, the DATA pin of the temperature and humidity sensor is in the input state, constantly detecting external signals and waiting for the host to call.

• Step 2: The I/O of the microprocessor (host) should be set to output at the same time, and the low-level holding time should not be less than 18ms (maximum not exceeding 30ms). Then, the I/O of the microprocessor should be set to the input state. Due to the pull-up resistor raising the level, the I/O of the microprocessor, i.e. the DATA data line of the temperature and humidity sensor, also increases accordingly. Waiting for the temperature and humidity sensor to respond, the signal is sent as shown in the figure:

• 

• Step 3:

• The DATA pin of the temperature and humidity sensor (slave/slave) detects a low level external signal and waits for the low level state of the external signal to end. After pulling up the waiting delay sequence, the DATA pin of the temperature and humidity sensor is in the output state, outputting a low level of 83 microseconds as the response signal, and then outputting a high level of 87 microseconds to notify the peripheral device to prepare to receive data. At the same time, the I/O of the microprocessor is in the input state. After detecting a low level of I/O (83 microsecond response signal from the temperature and humidity sensor), wait for the data to be received after 87 microseconds of high level, and send the signal as shown in the figure:

• Schematic diagram of sensor (slave/slave) response signal

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• Step 4:

• 
  

  The DATA pin of the temperature and humidity sensor outputs 40 bits of data, and the microprocessor receives 40 bits of data based on changes in I/O levels. The format of the bit data "0" is 54 microseconds low and 23-27 microseconds high, and the format of the bit data "1" is 54 microseconds low and 68-74 microseconds high.

  
  

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

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• end signal：

• After the DATA pin of the temperature and humidity sensor outputs 40 bits of data, it continues to output a low level for 54 microseconds before transitioning to an input state. Due to the pull-up resistor, the DATA line becomes continuously high, releasing the bus.

• At this time, the temperature and humidity sensor internally re measures the environmental temperature and humidity data, records and stores the data, and waits for the arrival of external signals.

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• Note: To ensure accurate communication of sensors, users should strictly follow the parameters and timing in the table and data timing diagram when reading signals

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• symbol	parameter	min	type	max	unit
  Tbe	Host start signal pull-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 high-level time	80	87	92	S
  TLOW	Signal "0", "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

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• 8、Application Information

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• 1 、Working and storage conditions

• Exceeding the recommended working range may result in temporary drift signals of up to 3% RH. After returning to the normal working bar, the sensor will slowly return to the calibration state. To accelerate the recovery process, refer to the next section on "Recovery Processing".

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• environment	temperature (℃)	humidity (RH)
  work environment	-20~60	5%~95%
  storage environment	-20~60  (recommendation 10~30)	5%~95%  (recommendation 40~70%)

• Prolonged use under abnormal working conditions can accelerate the aging process of the product.

• Avoid long-term exposure of components to condensation and excessively dry environments, as well as the following environments.

• A. Salt mist；                         B. Acidic or oxidizing gases, such as sulfur dioxide and hydrochloric acid；

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• 2 、Recovery processing

• Sensors placed under extreme working conditions or in chemical vapor can be restored to their calibration state through the following processing procedure.

• Processing program: Keep at 45 ℃ and<10% RH humidity conditions for 2 hours (constant temperature drying); Subsequently, maintain for more than 5 hours under humidity conditions of 20-30 ℃ and>70% RH.

• 3 、Temperature influence

• The relative humidity of a gas largely depends on temperature. Therefore, when measuring humidity, it is important to ensure that the humidity sensor operates at the same temperature as much as possible. If sharing a printed circuit board with electronic components that release heat, the sensor should be installed as far away from the heating electronic components as possible, and installed below the heat source while maintaining good ventilation of the housing. To reduce heat conduction, the pins of the sensor should minimize metal connections. The contact area between the solder pads of the sensor and the copper, tin, gold and other metal coatings on other parts of the printed circuit board should be minimized or the distance should be as large as possible, and a gap should be left between the two。

• 4 、Light influence

• Long term exposure to sunlight or strong ultraviolet radiation can lead to a decrease in performance.

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• 5 、The effects of exposure to chemicals

• The sensing layer of a resistive humidity sensor is susceptible to interference from chemical vapors, and the diffusion of chemicals in the sensing layer may lead to measurement drift and decreased sensitivity. In a pure environment, pollutants will be slowly released. The recovery process described above can accelerate the implementation of this process。

• High concentrations of chemical pollution can cause complete damage to the sensor sensing layer, leading to sensor failure.

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• 6 、Wiring precautions

• The quality of signal cables can affect communication distance and signal quality. It is recommended to use high-quality shielded cables.

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• 7 、note

• order   Manual welding requires a contact time of less than 3 seconds at a maximum temperature of 300 ℃.

• order   The peak welding temperature should not exceed 260 degrees Celsius and the time should be less than 5 seconds.

• order   It is prohibited to use alcohol, plate washing water, or other liquids to clean the device body or soak it in liquids.

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• 9、Key announcement

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

• Without the written consent of our company, no unit or individual is allowed to extract or copy any part or all of the content of this manual without authorization, and it shall not be disseminated in any form.

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• Disclaimers：

• In the products, services, or features you purchase, you shall be bound by the commercial contract and terms of Shenzhen Yuanjian Sensing Technology Co., Ltd. All or part of the products, services, or features described in this document may not be within the scope of your purchase or use. Unless otherwise agreed in the contract, our company makes no express or implied representations or warranties regarding the content of this document. Due to product version upgrades or other reasons, the content of this document may be updated periodically. Unless otherwise agreed, this document is for use only and all statements, information, and recommendations in this document do not constitute any express or implied warranties. Although our company strives to avoid errors in the writing process and translation of this article, due to editing or printing reasons, there may be text errors, and we are not responsible for any problems caused by this. The above specifications and test data are based on the sample as the test object, and there are discrete deviations in the actual product data. Our company reserves the right to make changes to product technical parameters within the scope permitted by law and without notice. Please refer to the actual product.

• If there is anything unclear or needs to be confirmed, please feel free to contact our company！