TERACOM TSM400-4-CP MODBUS CO₂ and Pressure Sensor

1. Short Description

The TSM400-4-CP is a multi-parameter sensor supporting the MODBUS RTU protocol over an RS-485 interface. It measures barometric pressure and CO₂ concentration using an advanced non-dispersive infrared (NDIR) sensing element. The CO₂ measurement principle relies on the absorption of infrared light by CO₂ molecules and is temperature-compensated for accuracy. The sensor features self-calibration for CO₂ measurements when exposed to fresh air (approximately 400 ppm CO₂). The barometric pressure sensing element is factory calibrated and requires no lifetime recalibration. The sensor is housed in a slim plastic enclosure designed for installation on standard flush-mounted/cavity wall boxes (Ø68mm) with 61mm installation openings.

2. Features

• LED indicator for communication status.
• Long-term stability achieved through digital signal processing.
• Self-calibration capability for CO₂ measurements in fresh air.
• RS-485 interface supporting up to 32 nodes.
• Configurable bitrate and other communication parameters.
• Firmware updatable via the interface.

3. Applications

• Indoor air quality (IAQ) monitoring.
• CO₂ storage facility leakage control.
• Smart ventilation systems.
• Monitoring CO₂ levels in restaurants and breweries.

4. Specifications

Physical Characteristics

• Dimensions: 81 x 81 x 30 mm
• Weight: 66 g

Environmental Limits

• Operating temperature range: -20 to 60°C
• Operating relative humidity range: 5 to 95% (non-condensing)
• Storage temperature range: -20 to 60°C
• Storage relative humidity range: 5 to 95% (non-condensing)
• Ingress protection: IP20

Power Requirements

• Operating voltage range (including -15/+20% according to IEC 62368-1): 4.5 to 26 VDC
• Current consumption: 25 mA@5VDC (Peak: 150 mA@5VDC)

CO₂ Measurements

• Range: 400 to 5000 ppm
• Accuracy: ± (40 ppm + 5%)
• Resolution: 1 ppm
• Calibration: Automatic, when exposed to fresh air for more than 30 minutes.

Pressure Measurements

• Range: 10 to 1200 hPa
• Accuracy (min): ±1.5 (at 25°C, 750 hPa)
• Accuracy (max): ±2.5 (at -20°C to +85°C, 300 to 1100 hPa)
• Resolution: 1 hPa

Warranty

• Warranty period: 3 years

5. Pinout

Diagram showing a connector with labels TERM, 1-W, +5+30V, GND, A+, B-.

6. Installation

The Two-Wire MODBUS definition, according to modbus.org, states that a MODBUS solution over a serial line should implement a "Two-Wire" electrical interface compliant with the EIA/TIA-485 standard. In this topology, only one driver has the right to transmit at any given time. A third conductor is required to interconnect all devices on the bus, serving as the common ground.

Diagram illustrating an RS-485 bus topology with terminators, master/slave devices, +5V, A+, B-, and GND connections.

Attention: For proper interface operation, terminators (120 ohm resistors) must be installed at both ends of the bus. The TSM400-4-CP device includes a built-in 120-ohm resistor; to terminate the line, the "B-" and "TERM" pins must be shortened. A daisy-chained (linear) topology is recommended for multiple sensors. UTP/FTP cables are mandatory for interconnection.

Images of TERACOM devices: TCW260, TSM400-4-CP, and TSH300 connected via RS-485.

7. Installation Tips

The location and mounting position significantly impact measurement accuracy. Follow these tips for optimal results:

• Install the sensor approximately 1.2-1.4 meters above the floor.
• To prevent solar radiation interference, avoid installing the sensor near windows or in direct sunlight.
• Ensure the sensor is installed in an area with sufficient air circulation.

Diagram showing dimensions for mounting the TSM400-4-CP sensor on a wall box. It indicates a 68mm diameter box and 61mm screw spacing, with specific measurements for mounting holes (e.g., 61.6 mm, 11.5 mm, 13.8 mm, 7 mm, 18 mm, R2.75, R1.75).

8. Status Indicator

The device status is indicated by a single LED located inside the enclosure:

• LED blinks every 1 second: Sensor is working properly.
• LED blinks every 3 seconds: No communication with the controller.
• LED does not blink: No power supply.

9. Factory Default Settings

To restore factory default settings:

1. Disconnect the sensor from the bus (switch off the power supply).
2. Press and hold the "config" button.
3. While holding the button, reconnect the sensor to the bus (switch on the power supply).
4. The "status" LED will be ON for 3 seconds, then flash for 7 seconds, and finally remain ON after the 10th second.
5. Release the "config" button. The sensor will restart with factory default settings.

10. Firmware Update

Firmware updates for the sensor can be performed using a TERACOM controller that supports MODBUS RTU or with the MBRTU-Config software. For detailed instructions, consult your dealer.

11. Modbus Address Table

This table lists the Modbus registers for the TSM400-4-CP sensor.

MSWF - Most significant word first - (bits 31 ... 16), (bits 15 ... 0); LSWF - Least significant word first - (bits 15 ... 0), (bits 31 ... 16); PDU address - Actual address bytes used in a Modbus Protocol Data unit. A "NaN" value is returned for unavailable floating-point values (e.g., in case of measurement error). * The settings will take effect after restarting the device by power-off, power-on.

12. Recycling

♻️ Recycle all applicable material.

Do not dispose of with regular household refuse.