The small resistance tester based on C8051F005 one-chip computer is designed

A one-chip computer has been utilized to design this survey meter, which directly displays the measured resistance on an LCD screen. The measurement range extends from 0 to 9999 kΩ, and the device can simultaneously store the measured data, which is then transmitted to a computer via a serial port. This allows for advanced data analysis and processing. The meter boasts an accuracy of 0.1% and employs a tetrapolar measurement method, ensuring that the resistance readings are not affected by lead wire size or contact resistance. The device is designed for ease of use, providing clear readings and superior accuracy compared to conventional electrical bridges. It is suitable for laboratory and research applications, particularly in fieldwork settings. The measurement process involves applying a known constant current to the resistance under examination, measuring the voltage drop across it. This voltage is amplified and converted to a 0-3V DC signal by an amplifier, which is then processed by the one-chip computer for display on the LCD. The design emphasizes high amplifier accuracy, low drift, high input impedance, and strong noise suppression and anti-jamming capabilities. The signal processing circuit includes a difference amplifier composed of operational amplifiers A1, A2, and A3, along with resistors R3, R4, and RW forming the feedback network. The circuit employs deep negative voltage feedback to achieve higher input impedance and strong common-mode rejection. The output voltage is directly proportional to the examined resistance RX. The amplifier's gain is set to 10, ensuring that the output voltage remains within the 0-3V range suitable for the analog-to-digital converter. High-accuracy, low-noise operational amplifiers are selected for the design, along with precision resistors to maintain stability and performance.

A comprehensive understanding of the circuit design and functionality of the survey meter can be derived from its operational principles and component selection. The tetrapolar measurement method is particularly advantageous as it mitigates errors caused by lead resistance and contact resistance, which are common in traditional measurement techniques. By using a known constant current source, the device ensures that the voltage drop across the resistance is accurately measured, facilitating reliable resistance readings.

The difference amplifier configuration is crucial in achieving high input impedance and minimizing the effects of common-mode signals. Operational amplifiers A1 and A2 are configured in a way that their common-mode voltages are equal, which helps in canceling out any noise and drift that might affect the measurement. The use of negative feedback in the amplifier circuit further enhances its stability and accuracy, allowing for precise amplification of the measured voltage drop.

The choice of high-accuracy, low-noise operational amplifiers and precision resistors is essential for maintaining the integrity of the measurements, especially when dealing with low resistance values. The design incorporates shielding techniques to prevent interference from external sources, ensuring that the readings remain accurate and reliable.

In conclusion, this survey meter represents a sophisticated integration of modern electronic components and design principles, resulting in a highly accurate and user-friendly device for resistance measurement. Its application in various fields, including laboratories and field research, underscores its versatility and effectiveness in providing precise electrical measurements.We have adopted the one-chip computer, utilize the advantage of the one-chip computer to design this survey meter. This survey meter can read out the resistance quantity measured from LCD display screen directly, the measurement limit is 10 2.

9999k, can store the data tested at the same time, then is sent into the upper computer by the serial port, pass the strong function of the upper computer, can analyze, deal with the data measured. The survey accuracy of this tester is up to 0. 1%, and adopt the tetrapolar measurement method, resistance quantity is not influenced by the lead wire size and contact resistance. Not only it is simple and convenient to measure, reading is ocular, and the survey accuracy, definition are also higher than the general electrical bridge.

It can be used for the laboratory, research institute, is especially suitable for the working site. It pursues local basic principles to be to adopt in examine at the resistance through the known constant current as above, take out the pressure drop on the resistance examined, amplify and change into 0- 3V direct-current volts by the amplifier, then send into the input terminus that C8051F005A/D changes, deal with the one-chip computer, pass the liquid crystal display direct display electric resistance value finally. Because of realizing the measurement of the minification resistance, require the definition of the amplifier to be high climax reach 10 V, The linear scale is good, input impedance is high, and demand to drift about low, noise suppression and antijamming capability are strong, we have designed the difference amplifier as signal processing circuit in Fig.

2 shows for this. This amplifier is made up of operational amplifier A1, A2 in fractional circuit of first difference, A3 makes up the fractional circuit of second difference, R3, R4, RW make up the FB network, has introduced the series negative feedback of the deep voltage, so there is higher input impedance, and A1, A2 all select as the input end with the phase terminal, then output voltage and drift voltage of their common mode are equal, pass the fractional circuit of A3 constituent difference again, can cancel each other, so it has very strong common mode inhibitory potencies and drift voltage of the minor output; A4 the intersection of voltage and reverse follower, function its grade is isolated enable. It is analyzed that this circuit can get the following equations. From 3 Know the type output voltage U4 is directly proportional to with the resistance RX examined. The multiple of the amplifier is made through R3, R4, RW, because the input voltage of the analog to digital converter is 0- 3V, the magnification that this instrument sets up the amplifier is 10 times, gets the direct-current volts of 0- 3V on U4 end.

In order to guarantee definition and stability of the amplifier, besides own advantage of the above-mentioned circuit, integrated operational amplifier A1, A2, A3 chooses high-accuracy, low-noise, low max495 that drifted about, the resistance of the feedback branch chooses the accurate resistance of the high-accuracy, low temperature coefficient, noise suppression that in addition has taken some shielding measures effectively and interfering with. Examined and adopted the tetrapolar i 🔗 External reference