1. Description

    TX721-A1B is a type of gas sensor developed based on non-dispersive infrared spectroscopy (NDIR) technology. It can detect gases such as methane and propane hydrocarbons. It adopts a diffuse air intake method and is suitable for gas detection and early warning in the industrial field. At the same time, it meets the requirements of intrinsically safe explosion-proof certification. The internal temperature/humidity compensation algorithm is added to adapt to different temperature environments. It has the characteristics of high sensitivity, anti-poisoning, long life, and use in hypoxic environments.

    The TX721-A1B gas sensor is equipped with an ultra-low power light source and detector. At the same time, the single light source and dual detector differential measurement principle is used to correct the test channel through the reference channel, which can effectively solve the influence of light source attenuation and environmental factors. The optical path part adopts coating processing technology to minimize the loss of infrared light during the reflection process and the problem of optical path oxidation. At the same time, the body is made of SUS304 material, which is non-toxic and not easy to get dusty or oily, and has a strong texture and is safe and healthy.

2.Parameters

3.Appearance and dimension

Pin Definition:

4.Characteristic curve

    The following figure is the sensor temperature, repeatability, linearity and accuracy characteristic curve, as shown in the figure：

5.Design reference:

    Because different industries have different requirements for sensors, in order to meet the requirements of various industries, the TX721-A1B sensor has many configuration parameters to solve some problems that may be encountered in different industries. A brief explanation is as follows:

(1) About the problem of automatic calibration at power on:

    Low-power LED infrared sensors are prone to zero drift (during transportation and installation) due to various reasons, such as deformation caused by temperature changes/shell extrusion (installation process), regional changes (pressure/humidity changes), so some customers find that the sensor has zero drift after the instrument is installed on site. It is recommended that customers perform the automatic power-on zero calibration function on their own instruments according to the protocol and their own situation. Customers who use analog quantities are recommended to directly turn on the power-on zero automatic calibration function of the sensor itself. It should be noted that after turning on this function, the power-on operation must be performed in clean air. If the power-on operation is performed under the condition of target gas, a huge negative value will be displayed after the sensor returns to the air. At this time, the sensor will determine that the previous zero calibration operation is wrong and will automatically re-mark back to zero.

(2) Regarding the ABC cycle (long-term zero drift automatic fine-tuning):

    During long-term use, the sensor drifts due to factors such as the attenuation of the light source and the pollution and deformation of the optical path. Therefore, the TX721-A1B sensor has two parameters, ABC and ABC factor. This function can be triggered under uninterrupted power supply conditions. Within a certain period (multiples of 8 hours), the sensor will record multiple sets of values for zero point correction. If the sensor's on-site environment is relatively harsh, the ABC factor (the absolute value of the sensor zero point reading corrected within each calibration cycle) can be set larger. Through setting, the maximum can reach 12% LEL.

(3) Regarding the false alarm problem caused by the rapid increase in humidity:

    The TX721-A1B is an infrared sensor that determines the gas concentration by the absorption of light of a specific wavelength by methane. If there is condensation in the optical path, the receiver will think that the light is absorbed by methane, thereby falsely alarming. In order to solve the problem of high humidity condensation in a rainy environment, our TX721-A1B sensor is equipped with a humidity sensor. Through the algorithm, the false alarm problem in a rainy environment is solved as much as possible without affecting the reliability of the sensor. Since the laboratory environment is very different from the real natural environment, such as the sharp increase in temperature and humidity in the actual natural environment, hot water showers in the shower room, etc., the sensor cannot fully take into account extreme conditions. Therefore, false alarms of the sensor under such extreme conditions are inevitable and reasonable. If there is no alarm under this condition, the reliability of the sensor will be greatly reduced. The manufacturer is expected to take this into consideration.

(4) Unstable sensor power supply caused by wireless signal transmission and sound and light alarms:

    Generally, battery-powered users use the TX721-A1B sensor. When the wireless gas detector transmits wireless signals or sound and light alarms, it is easy to affect the sensor power supply, resulting in insufficient power supply for the sensor to work properly. Attention should be paid during the development stage.

(5) Regarding intermittent power supply:

    The TX721-A1B sensor needs to be under the premise of automatic zeroing to ensure long-term zero point stability and linear accuracy. In addition, the sensor has a humidity algorithm to ensure that the sensor does not have false alarms in the case of condensation. The sensor needs to be powered continuously to trigger the function, so the sensor cannot work with intermittent power supply.