The power sensor is a detecting device capable of sensing information about the measured power and converting the detected data into an electrical signal or another required form of information to meet the needs of information transmission, storage, display, recording, and control. It serves as the first step toward achieving automated detection and control. Additionally, it transforms measured power parameters—such as current, voltage, power, frequency, and power factor—into DC current, DC voltage, or isolated analog or digital output signals. This product complies with the national standard GB/T13850-1998. Notably, true RMS voltage and current transmitters are employed to measure voltage or current signals with severe waveform distortions in the power grid, and they can also measure non-sinusoidal waveforms like square waves and triangular waves.
When the output information of the power sensor meets specific standard requirements, it is also referred to as a power transmitter. With the ongoing advancement of science and technology, industrial control or monitoring systems increasingly demand electrically isolated sensors, particularly concerning product stability, detection accuracy, and functionality. Analog products cannot match the performance and functionality of these sensors, such as nonlinear correction and small signal processing. Thus, the digitization of power sensors is an inevitable trend. Technologies involving sensing detection, sampling, and protection are gaining prominence, and current or voltage detection sensors have emerged to meet the demands of the times and are highly favored by Chinese power supply designers.
Key Parameters:
- Rated Output: 0 ~ 5Vdc; 0 ~ 20mA; 4 ~ 20mA;
- Accuracy: ±1.0%;
- Linear Range: 0 to 120%;
- Response Time: ≤300ms;
- Insulation Withstand Voltage: 2500V DC/1 minute;
- Operating Temperature: -20°C ~ +70°C;
General Technical Specifications:
- Reference Standards: GB/T13850-1998
- Relative Humidity: ≤93%
- Accuracy Class: 0.2, 0.5
- Storage Conditions: Temperature -40°C ~ +70°C, Relative Humidity 20% ~ 90%, No Condensation
- Operating Temperature: -10°C ~ +55°C
- Mean Time Between Failures: ≥30,000 hours
Classification Based on Input Signal Characteristics:
- DC Battery Sensors: Common types include shunts and resistor dividers.
- AC Power Sensors (suitable for power frequency sine wave measurement): Common types include electromagnetic voltage transformers, capacitive voltage transformers, and electromagnetic current transformers.
- Inverter Power Sensors (used for AC power measurement across various frequencies and waveforms): Examples include Hall voltage sensors, Hall current sensors, Rogowski coils, and variable frequency power sensors. Power frequency is a special case of variable frequency power, so variable frequency power sensors can generally be used as power frequency AC power sensors. Additionally, except for Rogowski coils which cannot measure DC, other sensors can also serve as DC power sensors.
Classification Based on Output Signal Characteristics:
- Analog Output Power Sensors and Digital Output Power Sensors. Variable frequency power sensors fall under the category of digital output power sensors.
Due to the strong anti-interference capability of digital signals and their ease of transmission via optical fiber, digital sensors can avoid losses and interference in the transmission link, offering a scientific approach to achieving high-precision measurement in complex electromagnetic environments. Given the diversity of power sensor products, this article focuses on introducing digital signal technology for AC signal power sensors. There are numerous ways to achieve sensor digitization, with the most common method being microprocessor technology like single-chip microcomputers, DSPs, and FPGAs, due to their flexibility and ability to implement various functions. With advancements in integrated circuits, specialized chips have emerged, such as those for watt-hour meters, providing digital interfaces and pulse outputs.
Related Information:
- Measurement Instruments:
1. The ARCM-NTC sensor directly acts on the measured device and converts it into the same or another kind of magnitude output based on certain rules.
2. The P/Q combination transmitter BD-3P/Q/I outputs standard signals.
3. A device or substance indicating the presence of a certain amount without providing a magnitude.
4. The power isolation sensor uses non-electrical media to isolate the measured power and outputs signals into a specified electrical signal between the measured power and the output signal.
Measurement Concepts:
- Measurement of the quantity to be measured.
- Measurement of influencing factors that affect the measured value or the amount indicated by the measuring instrument, such as frequency when measuring AC voltage.
Characteristics of Measuring Instruments:
- Accuracy refers to the ability of a metering device to approximate the true value of the measured quantity.
- Precision level is the degree of accuracy of the measuring instrument that meets certain measurement requirements while keeping its error within specified limits.
- Range modulus is the absolute value of the difference between the upper and lower limits of the measurement range.
- Reference operating conditions are the conditions specified for performance testing or ensuring consistent measurement results.
- Rated operating conditions are the normal conditions under which the metering characteristics remain within given limits.
- Extreme operating conditions are the extreme conditions set to prevent damage or permanent reduction of metering characteristics.
- Nominal values are marked to indicate characteristics or guide usage.
- Nominal input values specify the input range to keep the metering characteristics within given limits.
Measurement Errors:
- Absolute error is the difference between the measured result and the true value.
- Relative error is the ratio of the absolute error to the true value.
- Absolute error disregards the sign of the error.
Instrument Errors:
- Basic error is the inherent error under standard conditions.
- Additional error occurs under non-standard conditions.
- Reference error is the ratio of the absolute error to the range.
- Maximum deviation is the greatest difference between the standard curve and the specified straight line.
- Reversal error is the absolute difference between indicated values when the measuring instrument moves in opposite directions under the same conditions.
- Quantization error measures the deviation of the actual step characteristic from the ideal characteristic.
Values:
- RMS: The square root of the mean of the instantaneous values over one cycle.
- Average: The average of the instantaneous values over half a cycle.
This overview highlights the importance and functionality of power sensors in modern technology, emphasizing their role in ensuring precise measurements and reliable data transmission.
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