global sources TZ-CT01 CO₂ Transmitter User Manual

global sources TZ-CT01 CO₂ Transmitter

Overview

TZ-CT01 is a transmitter independently developed by our company tomeasureCO₂concentration. The sensing element adopts NDIR dual be infrared carbon dioxide sensor, which has a fast and sensitive response, avoiding the life and long-term drift problems of traditional electrochemical sensors, and is widely used in agricultural greenhouses, flower cultivation, edible mushroom cultivation and other occasions that require CO₂ monitoring. TZ-CT01 CO₂ transmitter is designed based on the RS485 communication interface, compatible with standard Modbus-RTU protocol, and can be connectedtoModbusnetwork to realize the measurement and monitoring of carbon dioxide concentration.TZ-CT01 adopts the DIP switch to set the address, which avoids the need to use the host computer to set the address in advance, simple, convenient, and easy to maintain and replace. TZ-CT01 adds a display screen and indicator lights, users can see the current carbon dioxide concentration more intuitively.

Features

• High long-term stability using dual-beam NDIR sensor
• High sensitivity and strong anti-interference ability
• High precision and good consistency
• Long life and low drift
• Gas sampling compatible with diffusion and vented
• Standard Modbus-RTU protocol
• Strong interface defense capability and stable communication

Application areas

Generally used in indoor clean environment, such as:

• Indoor air quality monitoring
• Greenhouse farms, agricultural greenhouses
• Flower cultivation, edible mushroom cultivation
• HVAC（Heating, ventilation and air conditioning）
• DCV（Fresh Air Energy Saving System）

Technical data

Specifications

1200 meters (depending on the use environment, transmission material and

transmission rate)

Number of theoretical nodes| 32
Operating temperature range| 0~50℃
Storage temperature| -20~60℃
Operating humidity range| 0~95%
Storage humidity| 0~95%
Dimensions| 109mm x 67mm x 40mm

PC electrical connection

when DC

power is supplied)

Red| V+| Power supply positive (connect to the positive end of the power supply when

DC power is supplied)

Schematic diagram of connection with PC

Note:
When setting up a RS485 network, pay attention to the RS485 grounding treatment to eliminate the common mode voltage. Suggest connecting the common ground of each transmitter together, and then connect it to the ground wire of the RS-232/RS-485 transmitter, you can use the shielding layer of the shielded wire as the ground wire.

DIP switch and address code

Note: The above picture is a schematic diagram of the DIP switch. The DIP switch has 8 DIP positions. The corresponding numbers from 1 to 8 are 128, 64, 32, 16, 8, 4, 2, 1, and these values are added together as the address code. As shown in the figure above, bits 1, 3, and 4 are in the ON position, so the address code is 128+32+16=176, that is, the address code is 176.

The above picture is a schematic diagram of the correct steps to turn on the DIP switch，

1. Step 1: Use a screwdriver to unscrew the screws in the four corners of the picture, as shown in the first step above.
2. Step 2: Turn on the DIP switch to set the address, as shown in the second step above. The part circled on the left is the power communication interface. The connection method has been explained in the electrical connection in 4.3, please read it carefully.

Note:
You can specify when ordering, we will preset it for you.

Protocol

For the Modbus-RTU protocol, please refer to the relevant information, here is only a brief introduction.

Data frame format

Note:
The above is the default format of the transmitter. If you need other formats, please specify when ordering.

RTU information format

TZ-CT01 follows the RTU information frame protocol. In order to ensure the integrity of the information frame, a pause time of 3.5 characters or more is required at the beginning and end of each information frame (T1-T2-T3-T4, the time can be calculated based on the specified baud rate), each byte of the information frame needs to be transmitted continuously. If there is a pause time greater than 1.5 characters, the transmitter will treat it as invalid information and will not respond.

Information frame format

Register definition

means the

transmitter is abnormal

| Read only
1| Relative humidity| The unit is 0.1%, MSB First,complement

format, 7FFF H means the transmitter is abnormal

| Read only
2| Reserved 1|  | Read only
3| CO₂ value| Unit ppm, MSB First, FFFFH means the

transmitter is abnormal

| Read only
4| RS485 address| Set by the DIP switch, the settable range is [1,255]| Read only
5| Baud rate| Support 4800bps/9600bps| Can read and

write

6| Hardware version|  | Read only
7| Software version|  | Read only

Address setting

You can specify when ordering, we will preset it for you, or you can modify it by yourself through the dial switch.

Baud rate setting

You can specify when ordering, we will preset it for you, or you can modify it by yourself through the serial port assistant.

Host reads transmitter information (function code 03)

The transmitter allows the host to use the function code 03 to read the CO₂ concentration measurement value of the transmitter and other information. The information frame format of the 03 code is as follows：

Host request information frame

Transmitter response information frame

Return the number of

bytes

| ****

10

Temperature data high

byte

| ****

7F

Temperature data low

byte

| ****

FF

Humidity data high byte| 7F
Low byte of humidity data| FF
1 high byte reserved| 00
1 low byte reserved| 00
CO₂ concentration data

high byte

| ****

04

CO₂ concentration data

low byte

| ****

59

Address code high byte| 00
Address code low byte| FF
Baud rate high byte| 25
Baud rate low byte| 80
Hardware version high

byte

| ****

07

Hardware version low byte| 01
Software version high byte| 00
Software version low byte| 10
CRC check code low byte| 87
CRC check code high byte| AE

Data parsing

• Temperature = 7FFFH = 32767, indicates no temperature data；
• Humidity = 7FFFH = 32767, indicates no temperature data；
• Reserved 1 = 0000H;
• CO₂ concentration = 0459H=1113, indicating that the CO₂ concentration is 1113ppm; Address code = 00FFH = 255;
• Baud rate = 2580H = 9600;
• Hardware version = 0701H;
• Software version = 0010H = 16 = V1.6

Note! If users only want to read the CO₂ concentration or other registers, they only need to read the corresponding registers.

Host setting transmitter information (function code 06)

This device can currently set the baud rate (register address is 0005H), and the message frame format is as follows:

Host request information frame

Transmitter response information frame

Data parsing: Set the baud rate to 9600
Abnormal response
When the host sends request information to the transmitter, various errors may occur. At this time, the transmitter sets the highest position of the function code to 1, and then returns an error code. The host can determine whether an error has occurred by detecting whether the highest bit of the function code is 1.

Error code

• 01: Illegal function code
• 02: Illegal data address
• 03: Illegal data value

CRC check code
RTU mode uses CRC-16 check, the check code occupies 2 bytes, if the check code is wrong, the transmitter will ignore the host’s request and not respond. The calculation method of the CRC-16 check code is as follows:

1. Preset a 16-bit register as hexadecimal FFFF, call this register CRC register;
2. XOR the first 8-bit binary data (the first byte of the information frame) with the lower 8 bits of the 16-bit CRC register, and place the result in the CRC register;
3. Shift the content of the CRC register one bit to the right (toward the low bit) and fill the highest bit with 0, check the right shift out position after shift;
4. If the shifted out bit is 0, repeat step ③ (shift one bit to the right again), if the shifted out bit is 1, the CRC register is XORed with the polynomial A001 (1010 0000 0000 0001);
5. Repeat steps ③ and ④ until the right shift is 8 times, so that the entire 8-bit data has been processed;
6. Repeat steps ② to step ⑤ to process the next byte of the message frame;
7. After calculating all the bytes of the information frame according to the above steps, the content of the CRC register obtained is: 16-bit CRC check code.

Dimensions (unit: mm)

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