Comet T6540

Remote CO2, Temperature and Humidity Monitor

Linkedin Twitter Google+

Key Features
  • Measures CO2 + Relative humidity + Temperature
  • Sends email alerts
  • Temperature Measuring Range -30 to +60°C
  • Relative Humidity range 0 - 100%
  • CO2 Concentration measurement 0 to 2000 ppm
  • LCD Display
  • Delivered with Calibration Certificate

The T6540 is a remote monitoring device for Temperature, Relative humidity and Co2

The CO2 (carbon dioxide) level is seen as essential paramter to measure in determining the climate for interiors of buildings. This includes, hospitals, schools, cinemas, theatres and care centres, factories and warehouses.

The T6540 is specifically designed to measure CO2, Temperature and Humidity, giving a complete picture of the climate inside a building, to optimize the level of ventilation.

The T6540 connects to the Local Area Network sends email alerts if the either the CO2, Temperature or Humidity level has exceeded the levels set by the user. Furthermore this unit comes with a display, so that live data can be viewed when required.

Data history can be downloaded to a spread-sheet for further analysis.

The unique patented auto-calibration procedure developed for the T6540 guarantees high reliability and long term stability and eliminates the need of periodical recalibration in the field.

High precision capacitive polymer sensor means that this product delivers values with excellent long term stability and ultimate accuracy.


T6540 digital temperature, humidity and carbon dioxide transmitter with Ethernet output technical overview

The T6540 is an integrated electronic temperature, humidity and CO2 sensor with an Ethernet output. It is designed to monitor these these environmental measurements and send the values back over the network to a central data logging system running on a PC or server. The measured values may also be obtained by browsing a web page built into the product. It is also able to generate alarm emails if any of the monitored temperature, humidity or CO2 measurements go outside of user set limits. An integrated LCD display shows the measured values locally. The display can be programmed to show some or all of the measured values cyclically. Measurements may be obtained from the T6540 electronically by downloading the XML file from the unit, or via Modbus TCP, SNMPv1 or SOAP protocols. A calibration certificate is supplied with the unit providing traceability of measured values back to national standards.

CO2 sensing is based on Non-Dispersive Infrared Technology (NDIR). It features auto-calibration that occurs every 24 hours to eliminate long term aging effects of the sensor. Measured values can be made either in a fast mode, or a slow averaged mode. Averaged mode averages out spikes that may otherwise occur when someone passes the sensor. The carbon dioxide concentration has a three-colour LED associated with it for "at a glance" indication of safety levels. The yellow and red LEDs can be can be assigned limits which when exceeded turn that lamp on. This is in addition to and independent of the thresholds used for sending email alerts.

T6540 setup

The T6540 temperature, humidity and CO2 transmitter may be set up simply using the TSensor configuration application or via the web interface built into the unit. Tsensor is a Windows based application that is able to find the unit once it has been attached to the network (using some network broadcast messages to identify the unit). TSensor allows all aspects of the T6640 to be configured, including the IP address and user adjustments of measured values (Warning: this may invalidate the calibration certificate!). For full information about how TSensor works, please refer to the TSensor webpage.

Alternatively, the web interface of the unit provides a convenient interface to be able to set up and configure all the important aspects of the unit. Any device with a web browser should be able to access and set up the unit as long as its IP address is known. As the web interface of the unit is available on the attached network, there is optional security at two levels that can be added. One to allow viewing of the web interface, the other to allow changes to the configuration to be made via the web interface.

Individual alarm levels for high and low limits may be assigned to the measured values of temperature, humidity and CO2, and also the calculated dew point. In addition, hysteresis may be added to each measured value and a programmable time delay (in seconds) that delays the onset of the alarm condition. When alarm limits are exceeded, the T6540 can send emails to up to three email addresses.

Temperature, humidity and CO2 over IP - protocol overview

  • Modbus TCP: Defaults to on. but may be turned off. Default Modbus port is 502, but this may be changed to other values.
  • SNMPv1: This is always available and protected by a user adjustable password. In addition, the sending of SNMP traps may be enabled to send traps to up to three users specified IP addresses.
  • SOAP v1.1: This may be enabled and allows the sending of SOAP messages at a user programmable interval to a target server at a specified IP address and port.

Full details of Modbus, SNMP and SOAP message formats are in the T6540 user guide.

Data logging carbon dioxide, temperature and humidity

A history of 1000 readings per measurement channel is held in the unit, and a graph of that history may be displayed in the web interface. The logging interval of the history is programmable between 10 seconds and an hour which translates to a graph showing historical data that is between 2.8 hours and 41.7 days in length. The history held on the unit may be downloaded as a .CSV file.

For 24/7 logging requirements, the T6540 may be interfaced with a back end data logging software package, DBS Sensor Monitor. This software package is designed to run on a server that has constant availability. Using the SOAP protocol, the T6540 pushed measurement and alarm information back to the DBS Sensor Monitor application. Full details may be found on the DBS Sensor Monitor page, but this package allows remote access and viewing of data from PCs that could be anywhere in the world, the sending of alarms (independently of the T6540), graphing and data export amongst other features.

Carbon Dioxide - a hazardous substance

In the UK, carbon dioxide is classed as a substance hazardous to health under the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Details may be downloaded from the Health and Safety Executive web site at The T6540 is able to monitor and log CO2 (and temperature and humidity) levels to demonstrate compliance with the health regulations, and to send out alarm messages if dangerous levels are measured. The dangers of carbon dioxide cannot be underestimated as it is a colourless and odourless gas. It has been responsible for a number of deaths in the UK which has resulted in prosecutions. See for example this BBC news story about Heineken UKs brewery. Sensormetrix believes that this product well help monitor and protect the work environment, alerting to dangerous levels of carbon dioxide.

CO2 and building regulations

The UK building regulations 2000, section F: Ventilation say that carbon dioxide levels may be used an an indicator of occupancy levels. This information can be used for smart building controls where ventilation is controlled by occupancy.

Specification Summary

Feature Specification
Temperature measurement range -30 to +80°C
Temperature measurement accuracy ±0.6°C
Temperature measurement resolution 0.1°C
Temperature measuring interval 2 seconds
Humidity measurement range 0 to 100%
Humidity measurement accuracy ±2.5%RH over 5% to 95%RH @ 25°C
Humidity measurement resolution 0.1%RH
Humidity measuring interval 2 seconds
Computed values Dew point, specific humidity, absolute humidity, mixing ratio, specific enthalpy
CO2 measurement range 0 to 2000ppm (10,000ppm as an option)
CO2 measurement accuracy ±(50ppm +2% of reading) @ 25°C and 1013Pa
CO2 measurement resolution 1ppm
CO2 measuring interval 15 seconds
Display LCD indicating temperature, humidity, computed value and CO2 concentration
Operating temperature range -30 to +60°C
Operating humidity range 5 to 95% RH
IP rating IP30
Power 9-30V dc, 1W max
Dimensions 88.5x147.5x39.5mm; stem length 75mm
Weight 170g
Calibration Certificate Included

Similar products

  • T5540 - CO2 only version of T6540
  • T5541 - High accuracy, CO2 only version of T6540 with CO2 sensor on a 1m lead
  • T6541 - High accuracy version of T6540 with RH+T on one 1m lead and CO2 sensor on a second 1m lead
  • H6420 - RS485 output version of T6540 with 2 relay outputs and audio alarm
Related Products