0 Introduction With the rapid development of wireless communication technology and computer technology and their application in sensor technology, wireless data acquisition of pressure sensors has become possible, offering superior performance compared to traditional pressure sensors. It can be applied to areas with difficult wiring and power supply, areas inaccessible to personnel (such as areas with high temperature, extreme cold, high humidity, pollution, or environmental damage), and some temporary situations, realizing remote testing of sensor systems, which is an inevitable trend in testing in the information age. 1 System Design The wireless data acquisition system for pressure sensors designed in this paper consists of a front-end sensor data acquisition and transmission section and an end-end data receiving section. Figure 1 shows the block diagram of the sensor data acquisition and transmission section (top) and the receiving section (bottom). The sensor data acquisition and transmission section consists of a pressure sensor, a temperature sensor, a signal processing section, a microprocessor (generally a single-chip microcomputer), and a wireless transmission circuit. The pressure and temperature sensors acquire the pressure and temperature values ​​of the surrounding environment. The signal processing section includes a front-end channel, a programmable amplifier, and an A/D converter. Its function is to extract and amplify the analog signal from the sensor under program control and perform analog-to-digital conversion. The microprocessor is responsible for controlling the operation of various components in the system and processing digital signals. Under the control of the microprocessor, the wireless transmitting circuit encodes and processes the collected information data using an encoder, and then transmits it via a transmitting module. The data receiving section consists of a wireless receiving circuit, a microprocessor, and a display section. Under the control of the microprocessor, it receives data transmitted via radio. After a set of formatted data is received, the decoder in the receiving circuit decodes the formatted data to obtain the current environmental pressure information, and then displays the pressure information on the LED receiving panel. 2 Hardware Implementation 2.1 Sensor The sensor uses a silicon piezoresistive pressure sensor with a temperature-sensing diode, encapsulated in a specially made metal shell, and connected to the external circuit via a multi-core cable. The four resistors of the piezoresistive sensor form a bridge circuit, excited by a 1 mA constant current source. The temperature-sensing diode is used to detect the ambient temperature to supply the microcontroller with temperature parameters. 2.2 Programmable Amplifier The programmable amplifier consists of analog switches, an input amplifier, and interface circuitry. Its function is to select the pressure signal and temperature signal in time under program control and send them to the input of the amplifier. At the same time, it can also select the corresponding gain of these two signals. After being amplified by the amplifier, the pressure and temperature voltage signals required by the A/D converter are output respectively for A/D conversion. The CD4052 we selected is a dual four-channel analog switch to select the pressure and temperature signals. The AD623 amplifier is an integrated single-supply instrumentation amplifier that can provide full power amplitude output under a single power supply (3~12 V). 2.3 A/D converter ICL7135 ICL7135 is a high-precision four-and-a-half-bit CMOS dual-slope A/D converter with the following characteristics: (1) The conversion speed is 3~10 times/s, the resolution is equivalent to 14-bit binary number, the conversion error is ±1 LSB, and the conversion accuracy is high. (2) The range is 0~1.9999 V. (3) It can identify the input analog signal over (under) the range; it has automatic conversion and automatic zeroing functions, which can ensure the long-term stability of the zero point at room temperature. (4) It can be directly connected to a microcontroller without the need for an address selection signal. When the ICL7135 operates in bipolar mode, the highest clock frequency is 125 kHz, and a 555 timer can be used as the CLK clock input of the ICL7135. When the integrator of the ICL7135 is in the integration process (integrating the signal and inverse integration), its BUSY terminal outputs a high level, and the integrator outputs a low level after the inverse integration crosses zero. The POL terminal of the ICL7135 is a polarity output terminal. When the input signal is positive, the POL output is high; when the input signal is negative, the POL output is low. B1, B2, B4, and B8 are BCD code output terminals. The accuracy and stability of the reference voltage of the A/D converter are the main factors affecting the conversion accuracy. To ensure the conversion accuracy of the ICL7135, we use a high-accuracy, low-temperature drift bandgap reference voltage source MC1403 to provide it with a 1 V reference voltage. The basic connection between the A/D converter and the microcontroller is shown in Figure 2. 2.4 Wireless Transmission Section The transmission circuit consists of a PT2262 encoder and an F05 transmission module. The PT2262 is a low-power, low-cost general-purpose encoder manufactured using CMOS technology, capable of compiling data and addresses into waveform codes. It has a maximum of 12 tri-state address pins (A0-A11) (floating, high, low), providing 531,441 possible address codes. It also has a maximum of 6 data pins (D0-D5), with the set address and data codes output serially from pin 17. The signal format is shown in Figure 3, and the encoding timing is shown in Figure 4. The F05 features a wide operating voltage range and low power consumption. When the transmission voltage is 3V, the transmission current is approximately 2mA, resulting in relatively low transmission power. 12V is the optimal operating voltage, providing good transmission performance with a transmission current of approximately 5-8mA. Above 12V, DC power consumption increases, and the effective transmission power no longer increases significantly. The F05 series uses AM modulation to reduce power consumption; when the data signal stops, the transmission current drops to zero. The data level should be close to the actual operating voltage of F05 to obtain a higher modulation effect. F05 is prone to decreased modulation efficiency and shorter transmission distance with excessively wide modulation signals. Transmission performance is better when the high-level pulse width is between 0.08 and 1 ms; efficiency begins to decrease after 1 ms. When the low-level region is greater than 10 ms, the first bit of the received data is easily interfered with (i.e., zero-level interference), causing decoding failure. If using CPU encoding/decoding, some random characters can be added before the data identification bit to suppress zero-level interference. If using a general-purpose codec, the oscillation resistor can be adjusted to make the low-level region in the middle of each code group less than 10 ms. Normally, the F05 input should be in a low-level state, and the input data signal should be a positive logic level, with an amplitude not exceeding the F05's operating voltage. F05 should be mounted vertically on the edge of the printed circuit board, at least 5 mm away from surrounding components to avoid oscillation stoppage due to distributed parameters. The transmitting circuit is shown in Figure 5. 2.5 Wireless Receiving Section The receiving circuit mainly consists of a PT2272 decoder and a J05 receiving module. The PT2272 can have up to 12 tri-state address pins (A0-A11), which can provide the 531441 address code in any combination. It can also have up to 6 data output pins (D0-D5), with pin 17 being the decoded valid indicator output. The PT2272 can be either latched or non-latched output. The J05 receiver module uses a superheterodyne, double-conversion structure. All RF reception, mixing, filtering, data demodulation, amplification, and shaping are completed within the chip, resulting in highly integrated receiving functionality. It offers two operating modes to suit different data rates. When pin 3 is floating (internal pull-up is set to high), the RF receiving bandwidth is wide, suitable for transmitters with large transmission frequency accuracy errors stabilized by surface acoustic wave (SAW) resonators and general LC transmitters. When pin 3 is grounded, the RF receiving bandwidth is narrower, and the demodulation filter bandwidth is larger, but the matching transmitter must have high frequency accuracy and stability, and the transmission frequency must be stabilized by a crystal or a high-precision SAW resonator. The receiver circuit is shown in Figure 6. 3 System Software Design 3.1 Software Implementation of the Front-End System The front-end system software of the intelligent pressure sensor consists of an initialization program, a pressure and temperature data acquisition program, a digital filtering program, a measurement algorithm program, and a transmission program. The source program flowchart is shown in Figure 7. The system initialization program includes setting the stack pointer, setting the interrupt source control word, and initializing relevant working units. For pressure signal selection, INT1 is used to request an interrupt. Data acquisition and other tasks are performed in the interrupt handler, as shown in Figure 8. A positive pulse is output from port P3.4, which is connected to the R/H pin of the ICL7135, to start the A/D conversion. During the A/D conversion, the STRB port is high. After the A/D conversion is complete, the STRB port outputs five negative pulses. An interrupt can be requested using the falling edge of the STRB port; five consecutive INT1 interrupts indicate one conversion result. The microcontroller's P0.0 to P0.3 ports read the BCD codes of the ten-thousands, thousands, hundreds, tens, and units digits sequentially through the B1 to B84-bit ports. Once all bits of the BCD code have been read and the data stored in the RAM, one pressure signal reading is complete. A similar method is used for gating temperature signals, which will not be elaborated here. Currently, there are many digital filtering methods, including arithmetic mean filtering, weighted average filtering, median filtering, and composite filtering. This system uses a composite filtering method. This method first ranks the n sampled values ​​by size, then removes the maximum and minimum values, and finally calculates the arithmetic mean of the remaining n-2 sampled values. Composite filtering can remove pulse interference and smooth the sampled values, combining the advantages of median filtering and arithmetic mean filtering. Regarding the thermal zero-point drift phenomenon of the pressure sensor caused by temperature, we use a normalization method based on nonlinear function polynomial fitting. In the program, the normalized polynomial is fitted to compensate for the temperature drift of the pressure value. Finally, the obtained pressure data is sent to the PT2262 data terminal via port P1, and then encoded by the PT2262 and transmitted to the F05 transmitter. 3.2 Software Implementation at the Receiver End The software implementation at the receiver end is relatively simple. The decoder PT2272 sends the data received from J05 to the P1 port of the microcontroller. After processing by the microcontroller, the data is sent to the LED display via the P2 port. See Figure 9 for the specific flowchart. 4. Analysis of Experimental Results During the test, the data acquisition and transmission circuit was placed approximately 20 m away from the signal receiving device. The pressure sensor was placed in a constant temperature bath, and group pressure tests were conducted at different temperatures. The experimental results are shown in Table 1. The experimental results show that because temperature information is integrated into the intelligent sensor system, and a polynomial fitting algorithm is used to calculate zero-point drift compensation for the pressure value, the influence of temperature on the pressure sensor output signal is basically eliminated. However, when the temperature increases, the error increases relatively, with a maximum error of [value missing]. Furthermore, this pressure sensor system uses wireless technology to transmit the acquired data, making it more flexible and reliable in application. Especially in harsh environments, it has advantages over traditional wired pressure monitoring systems, facilitating remote monitoring. This wireless data acquisition system for pressure sensors has broad application prospects.