The detection and the regulation of particle emissions are of great importance. The protocol is significant because it allows anyone to build, test and use a simple particle sensor. The advantage of the method lies not only in this simplicity, but also in the versatile possibilities of adapting the sensor shape to different needs with minimal equipment and minimal overall costs.
In addition to soot, the sensor can detect verities of charged particles and is suitable for many applications. For example, particular metal detection for power plants, wildfires in industries and automobiles. To begin manufacturing the electrodes take two copper pipes, having diameters of 18 millimeters and 22 millimeters respectively.
Measure nine millimeters from the top of both the pipes and mark these positions. Cut through the pipes using pipe cutter at the markings without applying too much force. Deburr the copper rings carefully without putting too much pressure on them and without scratching the electrode surfaces.
This is a critical step affecting the performance of the sensors. Next, before soldering the electrodes, polish the copper rings to get rid of the oxidized copper layer on the surfaces. Clamp the ring to be soldered in a vice.
Pre-tin both the copper ring and the cable before soldering the cable to the ring. Solder the red cable to the 18 millimeter inner copper ring and the black cable to the 22 millimeter outer copper ring. Stick the inner electrode holder onto the flow channel and wait for one hour to let the glue harden.
Then guide the cable through the cable channel making sure there is enough space for the soldering point. Place the 18 millimeter inner electrode ring on the holder. Next, feed the cable through the cable channel and place the 22 millimeter outer electrode ring on the respective holder.
Glue the outer electrode holder onto the flow channel. Insert the spacer into the gap between the two copper electrodes and wait one hour to let the glue harden. Seal all the cable channels with epoxy glue.
Then wait overnight for the glue to cure. On the next day, insert the vacuum seal in the printed valve of the outer electrode. Then, after inserting the two sensor sides into each other fasten them with the vacuum clamp.
Build the sensor set up as demonstrated in the picture. To do so, first, connect the high voltage power supply to the red sensor cable of the high voltage electrode. Then connect the black sensor cable to the bench multimeter voltage input.
Next, after collecting the electrometer ground or GND with a power supply GND connect the multimeter USB cable to the PC.Once the multimeter is connected to the PC incorporate the sensor into the aerosol measurement setup according to the shown layout. Make sure the dilution bridge is closed before starting the experiment. Connect the dilution bridge outlet to the aerosol mixer inlet and outlet two of the aerosol mixture into the sensor inlet.
Connect a high efficiency particulate absorbing or HEPA filter to the sensor outlet and connect the HEPA outlet to the mass flow controller or MFC inlet. Use a wye fitting and connect the aerosol mixer outlet one and the dilution airflow to the split end of the wye fitting. To the single end of the wye fitting connect the reference instrument inlet.
Start the experiment by connecting the aerosol generator to the dilution bridge making sure the dilution bridge is closed. Click Measure on the reference instrument. Slowly open the dilution bridge until the desired aerosol mass concentration of three to five milligrams per cubic meter is reached before logging data on the reference instrument.
Observe the reference instrument particle mass concentration. When the aerosol source is stable switch on the sensor power supply at 1, 000 volts and start logging the data. After an equilibrium state for accumulation and fragmentation of dendrites was reached, the sensor signal became proportional to the incoming soot concentration.
The vertical axis shows the sensor signal in amperes, and the horizontal axis shows the aerosol concentration measured by the reference instrument in milligrams per cubic meter. A linear fit with its representative parameters was calculated from the plot. Further, an experiment in which short circuit happened due to the formation of soot bridges within the electrodes showed the signal rising steeply in steps without stopping or flattening out.
Dendrites were no longer formed and the sensor was not in a state of equilibrium anymore. It is crucial to fabricate the electrodes very carefully and create a uniform electrode gap. To ensure a reliable test environment the experimental setup should be reproduced as demonstrated.
This protocol should motivate agencies, companies, research teams, and citizen scientists to reproduce this simple sensor construction and build their own particle detector.
