Can I ask how the air pressure sensor can achieve accurate height (altitude) measurement and ignore the influence of wind speed?

StruggleMySen

Can I ask how the air pressure sensor can achieve accurate height (altitude) measurement and ignore the influence of wind speed? [Copy link]

 

I am currently working on a project using the HP303B sensor, but this sensor is greatly affected by wind speed. How can I avoid this problem? The sensor is placed on a tower for attitude monitoring. How can I avoid the influence of wind speed on the sensor from the hardware or software perspective?

StruggleMySen

Please provide an idea, masters. My colleagues have tried many hardware compensation methods before, but none of them worked. For software, the compensation provided by the demo is enough.

yichun417

How is your structure designed, that is, the contact surface between the air pressure sensor and the atmosphere? I have a way to use a vertical tubular installation to prevent wind from entering the tube and causing measurement errors.

dcexpert

Measuring absolute altitude with air pressure is affected by many factors such as temperature, wind, humidity, etc., and it is difficult to achieve very high accuracy. It is possible to use a pressure sensor to measure altitude changes (relative altitude) through changes in air pressure.

风轻轻

Use more sensors, one for the east and one for the west. If the sensor is cheap, add one for the south and one for the north, one for up and one for down. Then, take the average of the measured values by removing the highest and the lowest score.

Then, the tube for measuring air pressure is twisted a little between the atmospheric opening and the sensor to offset the influence of certain changes in wind speed.

Then use a time-based averaging algorithm, for example, measure once every 1 minute, discard the values with too large variance from the measurements in the past hour, and then take the average value.

chunyang

Just add a wind shield, a sealing cover that is large enough, with an appropriate hole at the bottom to keep the air pressure inside and outside consistent.

风轻轻

Oh, if you want to measure the height instead of the air pressure, then it's easy. Isn't your sensor installed on the tower? Then measure it once every hour, and after measuring for a week, take all the values and calculate the regression line. The measured air pressure changes will definitely fluctuate based on the standard atmospheric pressure of that place. Once there is more data, the deviation can be eliminated. Since you have installed it on the tower, just keep measuring, and the value will definitely become more and more accurate.

Besides, why don't you replace it with a GPS or Beidou module? Measure the altitude directly instead of calculating it based on air pressure.

宋元浩

Affected by the environment

StruggleMySen

风轻轻发表于2020-7-21 16:11 Oh, if you want to measure the height instead of the air pressure, then it is simple. Isn't your sensor installed on the tower? Then measure it once every hour, ...

Thank you, I passed Beidou due to cost issues.

StruggleMySen

dcexpert published on 2020-7-21 14:34 Measuring absolute altitude with air pressure will be affected by many factors such as temperature, wind, humidity, etc., and it is difficult to achieve very high accuracy. Using air pressure sensors to measure the absolute altitude with air pressure...

How do you measure relative change?

damiaa

chunyang posted on 2020-7-21 16:03 Just add a wind shield, a large enough sealing cover, and open an appropriate hole at the bottom to keep the internal and external air pressure consistent.

This should work. Just test the air pressure. There is no need to let the wind blow directly. As long as there is air in, it will be fine. Keep the air pressure inside and outside equal.

StruggleMySen

StruggleMySen posted on 2020-7-22 11:04 How do you measure relative change?

Moderator, how can we use a pressure sensor to measure the relative height change through the change of air pressure?

chunyang

StruggleMySen posted on 2020-7-22 11:23 Moderator, how can I use a pressure sensor to measure relative height changes through changes in air pressure?

That is just a conversion process. Under most meteorological conditions, the air pressure will not change dramatically in a short period of time, so it can be roughly assumed that the value change of the air pressure sensor is the change in altitude, and then the corresponding altitude can be obtained by the table lookup method. However, given that the altitude measurement by the air pressure method is significantly affected by meteorological conditions, the altitude measurement of fixed points and slow-moving points under high-precision requirements should not use the air pressure method, but should be based on satellite positioning or mobile base station altitude measurement. The main application occasion for altitude measurement by the air pressure method is aircraft. For example, on an airplane, the barometric altimeter is a necessary airborne instrument. It must be equipped even in the presence of GPS and altimeter radar. It is an irreplaceable and important instrument on the aircraft.

chunyang

气压与高度的对应关系不是一个线性函数，这意味着同样的气压差，在不同海拔基础下对应的高度差是不同的，所以换算时必须先转换成海拔高度，然后再计算相对高度的变化。显然，这对于固定点和慢移点的测高（也包括测高差）非常不利，时间一长，气象条件的影响就会非常显著了。

It would be best if you could clearly explain the specific application and the requirements for high-precision measurement.

StruggleMySen

chunyang posted on 2020-7-22 12:16 The corresponding relationship between air pressure and altitude is not a linear function, which means that the same air pressure difference will correspond to different altitude differences at different altitudes, so...

It is like this. If we require the barometric altitude measurement here, we need to fix it on the tower for measurement, and the accuracy requirement is +-5cm. It is a bit difficult to use only the barometric pressure sensor. We considered Beidou before, but passed this idea due to the base station problem. . . Some implementations of specific projects can still be changed. I will give suggestions to the leader.

chunyang

StruggleMySen posted on 2020-7-22 13:05 It is like this. If we require the barometric altitude measurement here, it is fixed on the tower for measurement. The accuracy requirement is +-5cm. It is not enough to use only the barometric pressure sensor...

The height measurement error is required to be no more than 5 cm? Well, we have to go to the tower and get the surveying equipment to measure the height manually. Not only is it impossible to measure the height by air pressure, but it is also impossible to measure the height by satellite. Manual height measurement can meet the error requirements for relative height, but it is still extremely difficult to measure the absolute altitude. If you read the papers on the height measurement of Mount Everest, you will know how difficult it is.

chunyang

If the purpose of the project is to ensure that the tower construction is in compliance with the buried quality or to ensure that the equipment is installed in the designated location, then the idea is completely wrong. Electronic technology is not omnipotent, far from it.

Tell me clearly what you want to do.

StruggleMySen

chunyang posted on 2020-7-22 13:17 If the purpose of the project is to ensure that the tower construction is in compliance with the buried quality or to ensure that the equipment is installed in the designated location, then the idea is completely wrong. Electric...

It is used to detect the tower's posture and whether it has moved up or down.

chunyang

StruggleMySen posted on 2020-7-22 15:28 It is used to detect the posture of the tower and check whether it has any up and down displacement

That is simply impossible. It is a directional error. Don't bother. The change in the position of the tower indicates that there is foundation settlement. The process is very slow, and there is no direct, effective and reliable electronic technology available. The settlement of buildings, including towers, needs to be checked based on optical surveying and mapping. Unless it is in an area with very unstable geology, it is sufficient to sample and measure certain landmark buildings during the geological survey of the city at intervals of several years. There is no need to pay special attention to any tower. As long as the construction and related materials strictly comply with the specifications, you can rest assured for a long time. As for towers built in geologically unstable areas in the wild, just pay attention to them during regular inspections. There is no need for any special care. After all, it is not a livable area. Everything can be implemented in accordance with the requirements of relevant national standards.

StruggleMySen

chunyang posted on 2020-7-22 16:09 That is impossible to do. It is a directional error. Don't bother. The change in the position of the tower indicates that there is foundation settlement. The process is very slow and there is nothing...

Thank you for your patience. I would like to ask what solution is more suitable for this situation?