A current sensor is a detection device that can sense the information of the measured current, and can transform the sensed information into electrical signals that meet certain standards or other required forms of information output according to certain rules to meet the needs of Requirements for the transmission, processing, storage, display, recording and control of information.
Current sensors, also known as magnetic sensors, can be used in household appliances, smart grids, electric vehicles, wind power generation, etc. Many magnetic sensors are used in our lives, such as computer hard drives, compasses, household appliances and so on.
A current sensor is an active module, such as Hall devices, operational amplifiers, and final-stage power tubes, all of which require a working power supply and also consume power.
(1) The output ground terminal is centrally connected to the large electrolysis to facilitate noise reduction.
(2) The capacitor is uF, and the diode is 1N4004.
(3) The transformer is determined according to the power consumption of the sensor.
(4) The working current of the sensor. Direct detection type (without amplification) power consumption: maximum 5mA; direct detection amplification type power consumption: maximum ±20mA; magnetic compensation type power consumption: 20 output current; maximum consumption current 20 2 times the output current. The power consumption can be calculated from the consumed operating current.
Features of Current Sensors
Whether the sensor is open-loop or closed-loop, the basic performance is not very different. The basic advantages are: fast response time, low temperature drift, high precision, small size, wide frequency bandwidth, strong anti-interference ability, and strong overload ability.
How to choose a current sensor?
A. When selecting a current sensor, it is necessary to pay attention to whether the size of the perforation can ensure that the wire can pass through the sensor;
B. When selecting a current sensor, it is necessary to pay attention to whether the application environment of the site has special environments such as high temperature, low temperature, high humidity, strong earthquake;
C. When selecting a current sensor, it is necessary to pay attention to whether the spatial structure is satisfied;
Instructions for the use of current sensors
A. When wiring, pay attention to the exposed conductive parts of the terminals, try to prevent ESD shocks, and engineers with professional construction experience are required to perform wiring operations on this product. The connection wires of the power supply, input and output must be connected correctly, and must not be misplaced or reversed, otherwise the product may be damaged.
B. The installation and use environment of the product should be free of conductive dust and corrosiveness
C. Severe vibration or high temperature may also cause damage to the product, so you must pay attention to the occasion of use.
Precautions for the use of current and voltage sensors
(1) The current sensor must be properly selected according to the rated effective value of the measured current. If the measured current is excessive for a long time, it will damage the end-pole power amplifier tube (referring to the magnetic compensation type). Under normal circumstances, the duration of twice the overload current should not exceed 1 minute.
(2) The voltage sensor must be connected with a current limiting resistor R1 in series on the primary side according to the product description, so that the primary side can obtain the rated current. Under normal circumstances, the duration of 2 times the overvoltage shall not exceed 1 minute.
(3) The best accuracy of the current and voltage sensor is obtained under the condition of the rated value of the primary side, so when the measured current is higher than the rated value of the current sensor, a correspondingly large sensor should be selected; when the measured voltage is higher than the voltage sensor. When the rated value, the current limiting resistor should be readjusted. When the measured current is lower than 1/2 of the rated value, in order to obtain the best accuracy, the method of increasing the number of turns can be used.
(4) The sensor with insulation withstand voltage of 3KV can work normally in the AC system of 1KV and below and the DC system of 1.5KV and below, and the sensor of 6KV can work normally in the AC system of 2KV and below and the DC system of 2.5KV and below for a long time. , be careful not to use overpressure.
(5) When using it on a device that requires good dynamic characteristics, it is best to use a single copper-aluminum busbar that matches the hole diameter, and the dynamic characteristics will be affected by replacing the small one with a large one or having more turns.
(6) When used in a high-current DC system, if the working power supply is open or faulty for some reason, the iron core will generate large residual magnetism, which is worth noting. Remanence affects accuracy. The method of demagnetization is not to add working power supply, pass an AC on the primary side and gradually reduce its value.
(7) The ability of the sensor to resist external magnetic fields is: a current that is 5 to 10 cm away from the sensor is twice the current value of the primary side of the sensor, and the magnetic field interference generated can be resisted. When three-phase high-current wiring is used, the distance between phases should be greater than 5-10cm.
(8) In order to make the sensor work in the best measurement state, the simple and typical regulated power supply described in Figure 1-10 should be used.
(9) The magnetic saturation point and circuit saturation point of the sensor make it have a strong overload capacity, but the overload capacity is time-limited. When testing the overload capacity, the overload current of more than 2 times shall not exceed 1 minute.
(10) The temperature of the primary current busbar should not exceed 85℃, which is determined by the characteristics of ABS engineering plastics. If users have special requirements, high temperature plastics can be selected as the shell.
Advantages of current sensors in use
(1) Non-contact detection. In the reconstruction of imported equipment, as well as in the technical transformation of old equipment, the superiority of non-contact measurement is shown; the electrical wiring of the original equipment can be measured without any modification.
(2) The disadvantage of using a shunt is that it cannot be electrically isolated, and there is insertion loss. The greater the current, the greater the loss and the larger the volume. It is also found that the shunt has an inevitable electrical current when detecting high frequency and large current. Inductive, it cannot truly transmit the measured current waveform, and it cannot truly transmit non-sinusoidal waveforms. The current sensor completely eliminates various drawbacks above the shunt, and the accuracy and output voltage value can be the same as the shunt, such as the accuracy of 0.5, 1.0, and the output voltage of 50, 75mV and 100mV.
(3) It is very convenient to use. Take a LT100-C type current sensor, connect a 100mA analog meter or digital multimeter in series with the M terminal and the zero terminal of the power supply, connect the working power supply, and put the sensor on the wire loop. It can accurately display the current value of the main circuit 0 ~ 100A.
(4) The traditional current and voltage transformer, although there are many working current and voltage levels, has high precision under the specified sinusoidal operating frequency, but its suitable frequency band is very narrow, and it cannot transmit DC. In addition, there is an excitation current during operation, so this is an inductive device, making it only tens of milliseconds in response time. It is well known that once the secondary side of the current transformer is opened, it will cause a high voltage hazard. Multi-channel acquisition of signals is required in the use of microcomputer detection, and people are looking for methods that can isolate and acquire signals. The current and voltage sensor inherits the advantages of reliable insulation of the primary and secondary sides of the transformer, and solves the defect of the expensive and bulky transmission transmitter and the use of a transformer, and provides an opportunity for analog-to-digital conversion for automatic management systems such as computer detection. In use, the sensor output signal can either be directly input to a high-impedance analog meter or a digital panel meter, or it can be processed twice, the analog signal is sent to the automation device, and the digital signal is sent to the computer interface.
In high-voltage systems above 3KV, current and voltage sensors can cooperate with traditional high-voltage transformers to replace traditional power transmitters and provide convenience for analog-to-digital conversion.
(5) The traditional detection element is limited by many factors such as specified frequency, specified waveform, response lag, etc., and cannot adapt to the development of high-power converter technology. Effective AC/DC converters are combined into an integrated transmitter, which has become the best detection module known to people. In addition, the development of electronic power devices towards high frequency, modularization, componentization, and intelligence enables device designers to be handy, which will be an epoch-making fundamental change in the history of electronic power technology.
1. Wide measurement range: it can measure current and voltage of arbitrary waveforms, such as DC, AC, pulse, triangular waveform, etc., and even faithfully reflect transient peak current and voltage signals;
2. Fast response speed: the fastest response time is only 1us.
3. High measurement accuracy: its measurement accuracy is better than 1%, which is suitable for the measurement of any waveform. Ordinary transformers are inductive components, which affect the measured signal waveform after being connected. Its general accuracy is 3%~5%, and it is only suitable for 50Hz sine waveform.
4. Good linearity: better than 0.2%.
5. Good dynamic performance: the response time is fast, which can be less than 1us; the response time of ordinary transformers is 10~20ms.
6. Working frequency bandwidth: Signals in the frequency range of 0~100KHz can be measured.
7. High reliability and long average trouble-free working time: average trouble-free time >5
8. Strong overload capacity and large measurement range: 0---tens of amperes to tens of thousands of amperes.
9. Small size, light weight, easy to install.