Application of Tilt Sensor in Shipborne Antenna Control

A sensor is a device or device that can sense a prescribed measurement and convert it into a usable output signal according to a certain rule. As a key basic device of an information system, in recent years, it has received extensive attention at home and abroad. As one of the classic sensors, the tilt sensor is also being replaced by new materials, new principles, multi-functions, and new structures. The combination with digital technology and communication technology is getting closer and closer, and it is moving towards integration, intelligence and miniaturization. developing.

A sensor is a device or device that can sense a prescribed measurement and convert it into a usable output signal according to a certain rule. As a key basic device of an information system, in recent years, it has received extensive attention at home and abroad. As one of the classic sensors, the tilt sensor is also being replaced by new materials, new principles, multi-functions, and new structures. The combination with digital technology and communication technology is getting closer and closer, and it is moving towards integration, intelligence and miniaturization. developing.

2. Principle of tilt sensor

In order to measure the inclination angle between the measured object and the standard horizontal plane, an electrolyte-type sensor is often used. The picture shows a single-axis schematic diagram of a dual-axis sensor when it is slightly tilted. The sensor is composed of a sealed cylinder. The cylinder is filled with about half of the entire capacity of the fluid medium. The electrolyte is a viscous liquid. The cylinder is equipped with electrodes and is immersed. In the electrolyte, each electrode is led out by a pin. When the sensor is tilted, the liquid level remains level due to gravity, and the conductivity between the two electrodes is proportional to the length of the electrode immersed in the liquid. For example, at the tilt angle shown in the figure, the conductivity between the electrodes a and b is greater than the conductivity between the electrodes b and c. It can be seen that in terms of electrical characteristics, the sensor is similar to a potentiometer, and the impedance change is proportional to the tilt angle. The relationship between the sensor output signal and the tilt angle is shown in Figure 2. Note that when the tilt angle is greater than 20°, the output signal becomes Non-linear. It can be proved that the range of inclination angle that the sensor can measure is a function of electrolyte capacity, electrode spacing and electrode length. The sensor is similar to a lead-acid battery to a certain extent. The current can cause the chemical reaction of the electrolyte, and the final result will make the electrolyte lose its conductivity. Therefore, in order to prevent the electrolysis reaction from occurring, the sensor must be excited by an alternating current with a high enough frequency. For some electrolytes, this frequency can be 25Hz, while for some electrolytes, it needs to reach 1000Hz to 4000Hz.
 

Application of Tilt Sensor in Shipborne Antenna Control

Figure one

Application of Tilt Sensor in Shipborne Antenna Control

Figure 2 Sensor output characteristics

3. Application of tilt sensor in shipborne antenna control

3.1 The advancing of the ship and the turbulence of the waves will cause the random mount of the shipborne antenna to tilt. Therefore, in order to ensure that the antenna can continuously and accurately track the satellite, the antenna shaft frame must be adjusted in real time. In addition to the azimuth (Azimuth) and the elevation (Level), the antenna rotation control also has a vertical elevation (Cross level), so three angular velocity sensors to detect the motor speed and one tilt sensor to detect the level are used. as the picture shows:

Application of Tilt Sensor in Shipborne Antenna Control

Figure 3 Schematic diagram of shipborne satellite antenna

3.2 Sensor parameters and applications

Measuring range ±45°; input voltage +5v; output +1~4vDC or 4~20mA; resolution is 0.01°; non-linearity is ±2°; working temperature is -40°C~+80°C; impact resistance is 1000g, 1msec.

For a dual-axis sensor, it has similar properties to that of a single-axis sensor, but also includes its own complexity. Since the two axes share the central electrode, the four peripheral electrodes are ideally distributed at the four corners of the square, so two methods are used for independent measurement of each axis: one is that there is only one axial excitation at the same time, and the other is two-axis. Load different frequency excitations at the same time. As shown in the figure, the frequency of the excitation signal between electrodes a and c is twice that between electrodes d and e. Note that the two orthogonal axes in method one are diagonal ac respectively In the second method, the two orthogonal axes are the ae and ad directions of the peripheral electrode square.

Application of Tilt Sensor in Shipborne Antenna Control

Figure 4 Peripheral electrode waveform

3.3 Sensor interface circuit

Application of Tilt Sensor in Shipborne Antenna Control

Figure 5 Input circuit block diagram

It can be seen from the figure that because the sensor output is a weak analog signal, the analog output of the sensor must be preprocessed, also known as signal conditioning, and converted into digital after A/D conversion, before the processor can perform it. Analysis and processing. Specific to the electrolyte type inclination sensor, take a certain type of shipborne antenna as an example, the actual application circuit is shown in the following figure:

Application of Tilt Sensor in Shipborne Antenna Control

Figure 6 Sensor application circuit

U5 in the figure constitutes the inverting amplifier circuit for the sensor output CTR signal. F1 and F2 come from the processor output port control signal, which is a square wave with a frequency of 50HZ and a phase difference of 180°, which is driven by an inverter as the LV and CL electrodes of the sensor. , It can not only realize the alternate change of the signal polarity on each pair of electrodes, but also provide the choice of horizontal and vertical horizontal two-dimensional tilt measurement. F1 and F2 also act on the control terminals A and B of the multiple input selector U6, corresponding to the change of the signal polarity on each pair of electrodes, and select the signal that controls the corresponding polarity as the output.

4 Conclusion

The electrolyte type inclination sensor has good reproducibility, reliability and high accuracy. Special attention should be paid in the application: ⑴The driving signal F1, F2 must be an AC voltage signal with zero DC component, because DC will make the electrolyte An electrolysis reaction occurs and the conductivity is lost, causing irreversible damage to the sensor. ⑵Avoid using wave soldering and chemical organic solvent cleaning to prevent changes in sensor output characteristics and electrolyte leakage.

The author’s point of innovation: In order to ensure its reliable operation, a CMOS inverter should be connected between the processor port pins and the sensor. The microprocessor can be set to wake up once or several times per second to perform new measurements, while sampling the midpoint voltage of the drive signal as a reference, so that each measurement is completed in two steps: first calculate the value of the sensor signal minus the reference signal, and then add Invert the drive signal and calculate the value of the reference signal minus the sensor signal, subtract the two measurement results to get 2 times the required tilt value and offset the deviation generated by the system.

A sensor is a device or device that can sense a prescribed measurement and convert it into a usable output signal according to a certain rule. As a key basic device of an information system, in recent years, it has received extensive attention at home and abroad. As one of the classic sensors, the tilt sensor is also being replaced by new materials, new principles, multi-functions, and new structures. The combination with digital technology and communication technology is getting closer and closer, and it is moving towards integration, intelligence and miniaturization. developing.

A sensor is a device or device that can sense a prescribed measurement and convert it into a usable output signal according to a certain rule. As a key basic device of an information system, in recent years, it has received extensive attention at home and abroad. As one of the classic sensors, the tilt sensor is also being replaced by new materials, new principles, multi-functions, and new structures. The combination with digital technology and communication technology is getting closer and closer, and it is moving towards integration, intelligence and miniaturization. developing.

2. Principle of tilt sensor

In order to measure the inclination angle between the measured object and the standard horizontal plane, an electrolyte-type sensor is often used. The picture shows a single-axis schematic diagram of a dual-axis sensor when it is slightly tilted. The sensor is composed of a sealed cylinder. The cylinder is filled with about half of the entire capacity of the fluid medium. The electrolyte is a viscous liquid. The cylinder is equipped with electrodes and is immersed. In the electrolyte, each electrode is led out by a pin. When the sensor is tilted, the liquid level remains level due to gravity, and the conductivity between the two electrodes is proportional to the length of the electrode immersed in the liquid. For example, at the tilt angle shown in the figure, the conductivity between the electrodes a and b is greater than the conductivity between the electrodes b and c. It can be seen that in terms of electrical characteristics, the sensor is similar to a potentiometer, and the impedance change is proportional to the tilt angle. The relationship between the sensor output signal and the tilt angle is shown in Figure 2. Note that when the tilt angle is greater than 20°, the output signal becomes Non-linear. It can be proved that the range of inclination angle that the sensor can measure is a function of electrolyte capacity, electrode spacing and electrode length. The sensor is similar to a lead-acid battery to a certain extent. The current can cause the chemical reaction of the electrolyte, and the final result will make the electrolyte lose its conductivity. Therefore, in order to prevent the electrolysis reaction from occurring, the sensor must be excited by an alternating current with a high enough frequency. For some electrolytes, this frequency can be 25Hz, while for some electrolytes, it needs to reach 1000Hz to 4000Hz.
 

Application of Tilt Sensor in Shipborne Antenna Control

Figure one

Application of Tilt Sensor in Shipborne Antenna Control

Figure 2 Sensor output characteristics

3. Application of tilt sensor in shipborne antenna control

3.1 The advancing of the ship and the turbulence of the waves will cause the random mount of the shipborne antenna to tilt. Therefore, in order to ensure that the antenna can continuously and accurately track the satellite, the antenna shaft frame must be adjusted in real time. In addition to the azimuth (Azimuth) and the elevation (Level), the antenna rotation control also has a vertical elevation (Cross level), so three angular velocity sensors to detect the motor speed and one tilt sensor to detect the level are used. as the picture shows:

Application of Tilt Sensor in Shipborne Antenna Control

Figure 3 Schematic diagram of shipborne satellite antenna

3.2 Sensor parameters and applications

Measuring range ±45°; input voltage +5v; output +1~4vDC or 4~20mA; resolution is 0.01°; non-linearity is ±2°; working temperature is -40°C~+80°C; impact resistance is 1000g, 1msec.

For a dual-axis sensor, it has similar properties to that of a single-axis sensor, but also includes its own complexity. Since the two axes share the central electrode, the four peripheral electrodes are ideally distributed at the four corners of the square, so two methods are used for independent measurement of each axis: one is that there is only one axial excitation at the same time, and the other is two-axis. Load different frequency excitations at the same time. As shown in the figure, the frequency of the excitation signal between electrodes a and c is twice that between electrodes d and e. Note that the two orthogonal axes in method one are diagonal ac respectively In the second method, the two orthogonal axes are the ae and ad directions of the peripheral electrode square.

Application of Tilt Sensor in Shipborne Antenna Control

Figure 4 Peripheral electrode waveform

3.3 Sensor interface circuit

Application of Tilt Sensor in Shipborne Antenna Control

Figure 5 Input circuit block diagram

It can be seen from the figure that because the sensor output is a weak analog signal, the analog output of the sensor must be preprocessed, also known as signal conditioning, and converted into digital after A/D conversion, before the processor can perform it. Analysis and processing. Specific to the electrolyte type inclination sensor, take a certain type of shipborne antenna as an example, the actual application circuit is shown in the following figure:

Application of Tilt Sensor in Shipborne Antenna Control

Figure 6 Sensor application circuit

U5 in the figure constitutes the inverting amplifier circuit for the sensor output CTR signal. F1 and F2 come from the processor output port control signal, which is a square wave with a frequency of 50HZ and a phase difference of 180°, which is driven by an inverter as the LV and CL electrodes of the sensor. , It can not only realize the alternate change of the signal polarity on each pair of electrodes, but also provide the choice of horizontal and vertical horizontal two-dimensional tilt measurement. F1 and F2 also act on the control terminals A and B of the multiple input selector U6, corresponding to the change of the signal polarity on each pair of electrodes, and select the signal that controls the corresponding polarity as the output.

4 Conclusion

The electrolyte type inclination sensor has good reproducibility, reliability and high accuracy. Special attention should be paid in the application: ⑴The driving signal F1, F2 must be an AC voltage signal with zero DC component, because DC will make the electrolyte An electrolysis reaction occurs and the conductivity is lost, causing irreversible damage to the sensor. ⑵Avoid using wave soldering and chemical organic solvent cleaning to prevent changes in sensor output characteristics and electrolyte leakage.

The author’s point of innovation: In order to ensure its reliable operation, a CMOS inverter should be connected between the processor port pins and the sensor. The microprocessor can be set to wake up once or several times per second to perform new measurements, while sampling the midpoint voltage of the drive signal as a reference, so that each measurement is completed in two steps: first calculate the value of the sensor signal minus the reference signal, and then add Invert the drive signal and calculate the value of the reference signal minus the sensor signal, subtract the two measurement results to get 2 times the required tilt value and offset the deviation generated by the system.

The Links:   CM20MD-12H LTM201U1-L01

Author: Yoyokuo