A potential measuring instrument is an instrument used to measure potential difference (voltage). Its working principle is based on the basic principles of electricity and circuit characteristics. The following provides a brief analysis from the core principles, common types, and application scenarios:
1、 Fundamentals of Core Working Principles
Potential difference and Ohm's law
The essence of potential measurement is to measure the potential difference between two points. According to Ohm's law (V=IR), when a current I passes through a resistor R, a voltage V is generated across the resistor. A potential measuring instrument reflects the potential difference by detecting the voltage signal in the circuit.
Circuit connection method
Parallel measurement: The measuring instrument needs to be connected in parallel with the circuit under test, and the internal resistance of the measuring instrument should be sufficiently large (ideally infinite) to avoid measurement errors caused by shunt.
Impedance matching: In order to reduce the impact on the tested circuit, the input impedance of the measuring instrument is usually designed to be very high (such as the voltage range input impedance of a multimeter can reach 10M Ω or more).
2、 The working principle of common potential measuring instruments
1. Pointer multimeter (voltage range)
Principle of magneto electric meter head: Using the principle of force deflection of the energized coil in a magnetic field, the current size is reflected by the deflection angle of the meter head pointer, and then combined with a series resistor (voltage divider resistor) to convert the current into voltage value.
Voltage divider circuit: Connecting resistors of different resistance values in series can expand the range of measured voltage (such as DC voltage range and AC voltage range).
2. Digital Multimeter (DMM)
Analog to Digital Conversion (ADC):
The measured voltage is divided or attenuated before entering the ADC chip, which converts the analog voltage signal into a digital signal.
The digital signal is calculated by a processor and displayed as a voltage value (such as on an LCD screen).
3. Oscilloscope (voltage measurement function)
Waveform display and voltage measurement:
Input the voltage signal into the oscilloscope through the probe, and after amplification, display the waveform of the voltage variation over time on the display screen (such as CRT or LCD).
By calculating voltage values through vertical scales (VOLTS/DIV) and waveform amplitude, DC voltage, AC voltage, or pulse voltage can be measured.
3、 Key technical points
Anti interference design:
When measuring weak potentials (such as millivolts), electromagnetic interference should be shielded (such as using shielded wires or grounding) to avoid environmental noise affecting the measurement results.
Range selection:
Select the appropriate range based on the measured voltage to avoid overloading and damaging the instrument or causing measurement distortion (such as the automatic range function of a digital multimeter).
4、 Application scenarios
Electronic circuit testing: measuring the voltage at both ends of components, power output voltage, etc.
Research and Laboratory: High precision potentiometers are used for electrochemical experiments (such as electrode potential measurement), sensor signal acquisition, etc.
Industrial and Maintenance: Oscilloscopes are used to detect dynamic voltage waveforms (such as pulse signals, AC signals) in circuits.
summary
The core of a potential measuring instrument is to convert the potential difference into readable physical quantities (such as pointer deflection, digital display, waveform, etc.) through circuit design and signal conversion. Its accuracy and applicability depend on internal resistance, anti-interference ability, and the selection of measurement methods. In practical applications, it is necessary to choose the appropriate instrument type according to the scenario and pay attention to the operating standards to ensure measurement accuracy.