Summary of Antilog converter linearizes carbon dioxide sensor
### Summary This article presents a low-cost, pure hardware solution for linearizing the logarithmic response of the MG-811 electrochemical carbon dioxide sensor. Unlike typical methods requiring microcontrollers and complex calculations, this circuit uses an antilog converter to produce a linear output signal suitable for direct connection to panel meters or microcontrollers. The system offers high sensitivity, a wide measurement range (400–10,000 ppm), easy adjustment, and good accuracy without needing software-based log or antilog processing.
Parts used in the Antilog Converter Linearization Project:
- MG-811 CO2 sensor
- Buffer amplifier with extremely low bias current (<1pA)
- Microcontroller (for comparison context)
- Panel meter
- Microcontroller (alternative output destination)
While most carbon dioxide sensors use IR technology, electrochemical sensors are a serious competitor because of their high sensitivity, wide measurement range, and low price. As a rule, electrochemical sensors connect to a microcontroller through a buffer amplifier with an extremely low bias current (<1pA). The micro is needed to linearize the logarithmic response of the sensor. A good example of this approach is the SEN-000007 module from Sandbox Electronics, which uses an MG-811 CO2 sensor from Hanwei Electronics. Reference 1 reveals the circuits and the code, but does not specify accuracy.
This Design Idea shows a pure hardware solution to the linearization problem with a simple and cheap circuit that features easy adjustment and good accuracy. The output signal can go directly to a panel meter or a microcontroller, requiring no complex data manipulation such as log or antilog calculations.
The MG-811 sensor measures CO2 concentration from 400 to 10,000 ppm (0.04% to 1%). Figure 1 displays the transfer function of the sensor. The data points come from the datasheet of the MG-811. The line and equation are generated by the curve fitting tool of Microsoft Excel.
For more detail: Antilog converter linearizes carbon dioxide sensor
- Why are electrochemical sensors considered competitors to IR technology?
They offer high sensitivity, a wide measurement range, and a low price. - How does the proposed hardware solution handle the sensor's logarithmic response?
It uses a simple antilog converter circuit to linearize the output signal directly. - What is the measurement range of the MG-811 sensor?
The sensor measures CO2 concentration from 400 to 10,000 ppm. - Can the output signal connect directly to a panel meter?
Yes, the output signal can go directly to a panel meter without complex data manipulation. - Does this project require a microcontroller for linearization?
No, it provides a pure hardware solution that avoids the need for microcontrollers or code. - What calculation types are avoided by using this circuit?
The circuit eliminates the need for log or antilog calculations typically required by microcontrollers. - Is the circuit described as expensive?
No, the design features a simple and cheap circuit. - Where did the transfer function data points originate?
The data points come from the datasheet of the MG-811.
