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CO2 Sensor Simulator


The CO2 Sensor Simulator is a PC-controlled test device that plugs into any product utilizing the COMET CO2 Sensor (such as the CO2 Module). It generates all the analog and digital signals necessary to be recognized as a valid CO2 Sensor, and is capable of simulating various waveforms and CO2 concentrations.


The Simulator was designed to assist engineers in the development, test, and validation of capnography-based products. One or two Simulators can be controlled by the PC through the USB interface. The software provides access to the following functions:

  • generates capnography waveforms from text files

  • generates capnography waveforms from manually selected CO2 concentrations

  • introduces random respiration rates

  • introduces random waveform amplitude

  • introduces slow/wandering baseline

  • generates apnea condition

The software displays the following information:

  • CO2 waveform

  • CO2 trend (latest three hours)

  • End-of-Breath Parameters (etCO2, inCO2, RRavg, RR, Ti, Te)

  • Start-of-Breath and End-of-Breath waveform markers

  • Analog voltages

  • Lamp and Valve status

Custom waveforms can be created in text files and played back through the Simulator. These files can be designed in a spreadsheet or taken from patient data files. Engineers can use the Simulator to test hardware and software design integrity and test error conditions. Marketing can use the Simulator for user training and demonstrations. Service personnel can check the performance of returned goods or repairs.


Because the CO2 Sensor Simulator is PC-based, new test and diagnostic features can be added in the future simply by a software upgrade.



When the SIMULATOR software is run and a Simulator Pod is attached to the PC, the above screen is displayed. The user can select a Waveform File to be used or any of the Manual selections. The STOP/START button is used to begin waveform simulation. The lower Waveform screen displays the raw waveform being simulated, and the upper Trend screen displays three hours worth of etCO2/inCO2 trends. When the SIMULATOR is started, the CO2 Module may be turned on.


The SIMULATOR software contains the same Breath Detection Algorithm as the CO2 Module, and red and green markers on the waveform depict the start-of-expiration and start-of-inspiration points respectively. RR, etCO2, inCO2, Ti and Te are displayed for each detected breath.


When the SIMULATOR senses the solenoid valve of the CO2 Module turning on, it will automatically set the CO2 Sensor voltage level to mimic 0% CO2, so that a valid offset calibration may be performed. This offset calibration will not appear in the SIMULATOR Waveform screen or Trend Screen.


A gain calibration may be performed by selecting the appropriate concentration gas (ie. 5.0% CO2) manually, and then prompting the CO2 Module to initiate a gain calibration using the communication protocol between the CO2 Module and the medical device user interface.


A number of functions can be applied to the simulated waveform:

    • Randomize Respiration Rate

    • Randomize Waveform Gain

    • Slow Wandering Baseline

    • Speedup the breathrate

    • Apnea

The user may manually create waveforms using Manual Scroll Mode. When this mode is selected, moving the scroll bar control up and down causes the simulated CO2 concentration to change accordingly.


Custom waveform files can be created with text editors or spreadsheet programs. These files can be saved to the SIMULATOR application directory with all the existing waveform files. Real patient waveforms collected by the CO2 Module can be saved into files for later playback by the SIMULATOR.



TreyMed is a leading designer and manufacturer of respiratory care products and services.

We are a major supplier of OEM medical sensors and modules

to companies all over the world.

2007 TreyMed, Inc.  All rights reserved.