HOME ꄲ Smart Sensor ꄲ Environmental Monitoring Sensor ꄲ NDIR CO2 Carbon Dioxide Sensor

ꁆ ꁇ

NDIR CO2 Carbon Dioxide Sensor

PN:RK0801

Product Details

RK080X series infrared gas sensor. Used in indoor air quality testing, HVAC systems, fresh air equipment, air purification equipment, fans, automatic window control, etc., with good selectivity and stability. It is widely used all over the world.

For the design and manufacture of RK080x series infrared ground sensors, this manual provides important design technical suggestions. Please read this manual carefully before use.

Overview

This manual covers our infrared gas sensor RK0801 and RK0802. The design accuracy and size of these models are different. Table 1 summarizes the basic similarities and differences of these models.

RK080x series infrared sensors are designed and manufactured based on Lambert-Beer's law, used to detect target gases, and belong to physical sensors. Not affected by material consumption, the life span is generally longer than that of chemical sensors.

Table 1: Comparison of module models

Model	RK0801	RK0802
size	39.6x 17 x 9(mm)	33 x 17 x 9 (mm)
Design accuracy	±(50ppm+5% reading value)	±(50ppm+5% reading value)

Technical parameters
1. Technical parameters

Table 2: RK080x technical parameters

Model	RK0801	RK0802
measurement range	400～2000ppm (0-1%VOL optional)
working principle	Non-dispersive infrared (NDIR)
Operating Voltage	4.5～5.5V DC	4.5～5.5V DC
Working current	120mA peak 20mA average	120mA peak 20mA average
Precision	±(50ppm+5% reading value)	±(50ppm+5% reading value)
Preheat time	3min	3min
Response time	T90 <120s	T90 <120s
Detection interval	2s	2s
Working conditions	0～50℃/0～90%RH (no condensation)
Storage conditions	-20～60℃/0～90%RH (non-condensing)
Communication Interface	UART level 3.3V PMW

1. Interface definition
2. Table 3. RK080x interface definition

Pin	name	Features
PIN1、PIN8	CAL	Clean air zero point adjustment input
PIN2、PIN9、PIN12	NC	No connection
PIN3、PIN15	GND	Ground potential
PIN4、PIN16	VDD	Supply voltage
PIN5、PIN11	RXD	UART (RXD) data input
PIN6、PIN10	TXD	UART (TXD) data output
PIN7、PIN13	PWM	Pulse width modulation

Power supply impact

In order to ensure the normal operation of the sensor, the operating voltage of the sensor is kept in the range of 4.0V~5.5V DC. Exceeding this voltage range may cause malfunction or the sensor cannot work normally.

In order to ensure the normal operation of the sensor, the current output capacity of the power supply should not be less than 150mA. If the power supply current capacity is lower than this value, it may cause a malfunction or the sensor cannot work normally.

4. Interface design

RK080x infrared gas sensor provides multiple output interfaces such as UART and PWM, which can be individually calibrated. It is very convenient to connect the product with the user.

4.1 UART interface

The UART interface is the interface with the most complete functions of this sensor. It is recommended that users use the UART interface. The user-end equipment can read the gas concentration value directly through the sensor's UART interface.(The user terminal needs to use TTL level, if it is RS232 level, please perform level conversion first).The VDD-GND-RXD-TXD of the sensor is connected to the user's 5V-GND-TXD-RXD respectively.

4.1.1 Communication interface settings

If the user uses the UART interface, set the UART communication mode according to the following table.

Table 4. UART settings

Baud rate	9600
Data bit	8-bit
Stop bit	1 bit
Parity bit	no

4.1.2 Communication commands

Table 5. Communication command list

Protocol command interface list and meaning
0x86	Read gas concentration value
0x87	Calibration zero (ZERO)
0x88	Calibration span point (SPAN)
0x79	Turn on/off the automatic zero calibration function

0x86-Read gas concentration value
send command
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	Reserved	command	-	-	-	-	-	Check value
0xFF	0x01	0x86	0x00	0x00	0x00	0x00	0x00	0x79
return value
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	command	8 bits higher in concentration	Concentration lower 8 bits	-	-	-	-	Check value
0xFF	0x86	HIGH	LOW	-	-	-	-	Checksum
*Gas concentration value = HIGH 256 + LOW**

0x79-open/close automatic zero calibration
send command
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	Reserved	command	-	-	-	-	-	Check value
0xFF	0x01	0x79	0xA0/0x00	0x00	0x00	0x00	0x00	Checksum
return value
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	command	status	-	-	-	-	-	Check value
0xFF	0x79	0x01/0x00	-	-	-	-	-	Checksum
Note: When Byte3 in the sending command is 0xA0, the automatic calibration function is turned on; when Byte3 is 0x00, the automatic calibration function is turned off. The sensor factory default is to turn on the automatic zero calibration function. In the return value, Byte2 is the status, 0x01 indicates that the modification is successful, and 0x00 indicates that the modification fails.

0x87-Zero point calibration command
send command
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	Reserved	command	-	-	-	-	-	Check value
0xFF	0x01	0x87	0x00	0x00	0x00	0x00	0x00	Check value
return value
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	command	status	-	-	-	-	-	Check value
0xFF	0x87	0x01/0x00	-	-	-	-	-	Checksum
Note: Byte2 in the return value is the status, 0x01 indicates that the calibration is successful, and 0x00 indicates that the calibration has failed. The zero point refers to 400ppm. Before sending the zero point calibration command, please make sure that the sensor runs stably at a concentration of 400ppm for more than 20 minutes.

0x88-Calibrate SPAN point command
send command
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	Reserved	command	SPAN high 8 bits	SPAN lower 8 bits	-	-	-	Check value
0xFF	0x01	0x88	HIGH	LOW	0x00	0x00	0x00	Checksum
return value
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	command	status	-	-	-	-	-	Check value
0xFF	0x88	0x01/0x00	-	-	-	-	-	Checksum
Example: If the SPAN value is 2000ppm, then HIGH = 2000/256; LOW = 2000% 256 Note: Byte2 in the return value is the status, 0x01 indicates that the calibration is successful, and 0x00 indicates that the calibration has failed. Please calibrate the zero point before calibrating the SPAN value. Before sending the SPAN calibration command, please ensure that the sensor runs stably for more than 20 minutes at the corresponding concentration. It is recommended to use 2000ppm as the SPAN value for calibration. If you need to use a lower value as the span value, please choose a value above 1000ppm.

4.1.3 Checksum

In order to enhance the reliability of sensor communication, a checksum setting is added to the communication protocol. If the checksum fails, communication is not possible. The specific checksum calculation method is as follows:

Checksum = (Invert (Byte1+Byte2+Byte3+Byte4+Byte5+Byte6+Byte7))+1.

example:
Byte0	Byte1	Byte2	Byte3	Byte4	Byte5	Byte6	Byte7	Byte8
Start byte	Reserved	command	-	-	-	-	-	Check value
0xFF	0x01	0x86	0x00	0x00	0x00	0x00	0x00	Checksum
The calculation is as follows: Add from Byte1 to Byte7: 0x01 + 0x86 + 0x00 + 0x00 + 0x00 + 0x00 + 0x00 = 0x87 Invert: 0xFF-0x87 = 0x78 Add 1 after inversion: 0x78 + 0x01 = 0x79

C language checksum calculation routine:

C language calculation checksum routine

char getCheckSum(char *packet)

{

char i, checksum;

for( i = 1; i< 8; i++)

{

checksum += packet[i];

}

checksum = 0xff – checksum;

checksum += 1;

return checksum;

}

4.2 PWM interface

RK080x series sensors provide PWM interface, which uses pulse width to characterize target gas concentration. Take a sensor with a measurement range of 2000ppm as an example:

CO2 concentration output range	0～2000ppm
cycle	1004ms±5%
High level output at the beginning of the cycle	2ms (theoretical value)
Middle cycle	1000ms±5%
Low level output at the end of the period	2ms (theoretical value)
The formula for obtaining the current CO2 concentration value through PWM: Cppm=2000×(TH-2ms)/(TH+TL-4ms)
Cppm is the CO2 concentration value obtained by calculation, the unit is ppm TH is the time when the output is high in an output cycle TL is the time when the output is low in one output cycle

5.Calibration

RK080x series sensors have two calibration methods: zero point calibration and SPAN point calibration.

5.1 Zero point calibration

In order to facilitate the user to calibrate the zero point, RK080x series sensors have three zero calibration methods: manual zero calibration, command zero calibration and automatic zero calibration. The zero point calibration function refers to calibrating 400ppm.

5.1.1 Manual zero point calibration

Manual zero point calibration is to input a low level (0V) to the CAL pin of the sensor to calibrate the zero point. The low level needs to last for more than 7 seconds. Before calibrating the zero point, make sure that the sensor runs stably for more than 20 minutes at a concentration of 400ppm.

5.1.2 Automatic zero point calibration

The automatic calibration function means that the sensor will intelligently judge the zero point according to the environmental concentration and calibrate itself after a period of continuous operation. The calibration cycle is automatically calibrated once every 26 hours since power-on and operation. The zero point for automatic calibration is 400 ppm.

The automatic zero calibration function is suitable for office environment and home environment. But it is not suitable for agricultural greenhouses, breeding farms, cold storage and other places. In such places, the automatic zero calibration function should be turned off. After closing, the user is required to perform zero point detection on the sensor regularly, and if necessary, command zero calibration or manual zero calibration.

5.1.3 Command zero calibration

Sending calibration commands to the sensor through the serial port (UART) can realize the zero point calibration of the sensor. For the zero point calibration command, please refer to the 0x87-zero point calibration command in the communication.

5.2 SPAN point calibration

Send a calibration command to the sensor through the serial port (UART) to realize the SPAN point calibration of the sensor. For SPAN point calibration command, please refer to 0x88-Calibrate SPAN point command in communication.

Printed circuit board and shell design
1. The influence of the position of the sensor

Infrared sensors are physical sensors and only reflect light inside. Normally, the installation position of the sensor has no effect on the measurement.

1. Temperature sensor

The infrared sensor is temperature sensitive. In order to accurately measure the ambient temperature around the sensor, the location of the temperature sensor should be as close as possible to the sensor.

1. Sensor housing design

In order to make the measurement response speed fast enough, the air-permeable part of the sensor housing should be designed to be permeable, and the sensor should be close to the housing opening. It is recommended to use a design with openings on both sides of the housing to improve air flow.

Packaging design

Infrared sensors are physical sensors that detect gas concentration by light intensity. The physical shape of the sensor may be affected by vibration and pressure during the calculation process, and the sensor measurement may be affected and deviate from the original calibration range. Therefore, it is possible to make shock absorption design in packaging design. Such as adding pearl sponge or foam to the packaging to absorb shock.

ꄴ上一个： Indoor 11-in-1 Environmental Monitoring sensor

ꄲ下一个： 8-in-1 Environmental Monitoring Sensor with RS485

Company Product Follow us

Jinan Rainbow Technology is a high-tech enterprise with MEMS sensor and New energy as its core. It was established in Jinan, Shandong, China and has an R&D center in New York, USA.

Our products will play a critical role in the transition to a clean energy and green economy, it can be widely used in many fields such as Hydrogen Fuel cell, medical devices, air purification, gas detector, lithium battery safety monitoring, Hydrogen leak detection, smart home, and security IoT to meet the needs of safety, health, and energy conservation.

Through continuous technological innovation, we powering the Clean Energy transition, and provide our customers with more competitive materials. We have core capabilities in design, manufacturing and testing to provide customers with high precision and highly reliable products and One-Stop Solutions.
Our company has core invention patents and has passed ISO9001 quality system certification. Our products comply with RoHS and REACH environmental protection standards.

With the goal of standing at the forefront of technology, we are committed to promoting the development of Hydrogen energy with the spirit of "protecting homes with core technology and innovating to change lives".