The power sensor serves as a detecting device capable of sensing the information of the measured power and converting the detected data into an electrical signal or another form of information needed to meet requirements for storage, display, recording, and control. This makes it the initial step towards achieving automatic detection and automatic control. Additionally, it transforms measured power parameters like current, voltage, power, frequency, and power factor into DC current, DC voltage, and isolates the output analog or digital signals. The product adheres to the national standard GB/T13850-1998. Notably, true RMS voltage and current transmitters are used to measure voltage or current signals with severe waveform distortions in the power grid and can also measure non-sinusoidal waveforms such as square waves and triangular waves.
When the output information of the power sensor meets certain standard requirements, it is also referred to as a power transmitter.
With the continuous advancement of science and technology, industrial control or monitoring systems increasingly demand electrical isolation sensors, particularly concerning product stability, detection accuracy, and functionality. Analog products cannot match the performance and functionality of digital products, such as nonlinear correction and small signal processing. Thus, the digitization of the power sensor is an inevitable trend. Power technology with sensing detection, sampling, and protection is becoming a trend, and current or voltage sensors have emerged as required by the times, gaining favor among 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;
- Isolation Withstand Voltage: 2500V DC / 1 minute;
- Operating Temperature: -20°C ~ +70°C;
General Technical Conditions:
- Reference Standards: GB/T13850-1998
- Relative Humidity: ≤93%
- Accuracy Level: 0.2, 0.5
- Storage Conditions: Temperature -40~+70°C, Relative Humidity 20~90%, No Condensation
- Operating Temperature: -10~55°C
- Mean Time Between Failures: ≥30000h
Basic Classification:
Based on the characteristics of the input signal, it can be divided into:
- DC Battery Sensors: Common examples include shunts and resistor dividers.
- AC Power Sensors (suitable for power frequency sine wave measurement): Common types include electromagnetic voltage transformers, capacitive voltage transformers, electromagnetic current transformers, etc.
- Inverter Power Sensors (for AC power measurement of various frequencies and waveforms): Such as 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. Besides, except for the Rogowski coil, which cannot be used for DC measurement, the other sensors can also serve as DC power sensors.
Power isolation sensors are categorized into six types based on the detection of power signals and functions:
- Current Sensors
- Voltage Sensors
- Frequency Sensors
- Power Sensors
- Temperature Sensors
- Cross-line Alarm Sensors
According to the characteristics of the output signal, they can be divided into:
- Analog Output Power Sensors and Digital Output Power Sensors, where variable frequency power sensors are digital output power sensors.
Since digital fuel cells can directly output digital quantities, the A/D acquisition module can be omitted in many applications, alleviating system design work. Furthermore, compared to analog quantities, digital signals have stronger anti-interference capabilities, especially since digital signals can be conveniently transmitted via optical fibers, avoiding losses and interferences in the transmission link entirely, and providing a scientific method for achieving high-precision measurements in complex electromagnetic environments.
Given the variety of power sensor products, this article only introduces digital signal technology for AC signal power sensors. There are many ways to achieve the digitalization of power sensors. Currently, the most common method is microprocessor technology such as single-chip microcomputers, DSPs, and FPGAs due to its flexibility and ability to implement various functions. With the continuous development of integrated circuits, many specialized chips have emerged, such as watt-hour meter products, offering numerous specialized chips including digital interfaces and pulse outputs.
Related Information:
Measuring Instruments:
1. Sensor ARCM-NTC directly acts on the measured device and can convert it into the same or another kind of magnitude output according to certain rules.
2. Transmitter BD-3P/Q/I outputs a standard signal sensor.
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 output signals into a specified electrical signal between the measured power and the output signal.
Two Measurements:
1. The quantity to be measured is measured.
2. The influencing quantity is not the measured object but affects the measured value or the amount indicated by the measuring instrument. For example, frequency when measuring AC voltage.
Three Measuring Instrument Characteristics:
1. Accuracy measures the ability of a metering device to approximate the true value of the measured quantity.
2. The level or grade of accuracy of the measuring instrument (which meets certain measurement requirements and keeps its error within specified limits).
3. The modulus of the difference between the upper and lower limits of the measurement range |Upper limit value - Lower limit value|.
4. Standard operating conditions (reference operating conditions) for the use of measuring instruments specified for performance testing or to ensure that measurement results are effectively aligned with each other.
5. Rated operating conditions specify the normal conditions of use for the specified metering characteristics of the measuring instrument to remain within given limits.
6. Extreme operating conditions specify the extreme conditions to prevent damage to the measuring instrument or to permanently reduce the metering characteristics.
7. Nominal value marked on the appliance to indicate its characteristics or to guide the use of the value.
8. Nominal input value specifies the input value or input range of the measuring instrument to keep the metering characteristics within given limits.
Four Measurement Errors:
1. The difference between the absolute error measurement result and the measured true value (expected value, ideal value).
2. The ratio of the absolute error of the relative error measurement to the true value being measured.
3. The absolute value of the error does not consider the error value of the sign.
Five Measuring Instrument Errors:
1. Basic error (inherent error) the error that the measuring instrument has under standard conditions.
2. Additional error (impact error) the error that the measuring instrument has under non-standard conditions.
3. Reference the ratio of the absolute error of the error measuring instrument to its range.
4. Maximum deviation between the linear error standard curve and the specified straight line.
5. Return error is the same under the same conditions, the measured value is unchanged, and the stroke direction of the measuring instrument is different from the absolute value of the difference between the indicated values.
6. The deviation of the actual step characteristic and the ideal characteristic from which the quantization error is measured.
Six Values:
1. RMS: The square root of the mean of the instantaneous value over a period of one cycle. Or æ›° "root mean square value". Vrms = = Vp = 0.707 Vp
2. Average: The average of the instantaneous values ​​over a half cycle. Vavg = = Vp = 0.636 Vp
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