The current transmitter is divided into two types: DC current transmitter and AC current transmitter. The AC current transmitter is an instrument that can convert the measured AC current into a linear proportional output DC voltage or DC current. The products are widely used in electrical equipment of electric power, post and telecommunications, petroleum, coal, metallurgy, railway, municipal and other departments. , automatic control and scheduling system.
The current transmitteris a measuring module that converts the measured alternating current into a direct current or direct current voltage signal proportional to the primary current using the principle of electromagnetic induction, and is highly insulated between the primary and secondary sides, and the JTIA series AC current is transmitted. The device has the characteristics of high precision, high linearity, high integration, simple structure, long-term stability and adaptability to various working environments. It is widely used in system control and detection of electrical equipment in electric power, petroleum, coal, chemical, railway, communication, building automation and other industries.
1. Need to detect single-phase current or three-phase current: Current transmitters usually have two forms, which can be used to detect single-phase or three-phase current. For example, "2" in JLT2I means that "43" in single-phase current transducer JLT43I3 represents a three-phase current transmitter.
2. Range of input current of the transmitter: Due to the large range of actual load current change, in order to adapt to this situation, we usually use a current transformer to convert the large current into a small current of 1A or 5A. Therefore, the input of the current transducer is usually selectd according to the secondary current of the current transformer. Output DC signal variation range: The international output signal standard is usually DC 4-20mA. Of course, the output DC signal can also be DC voltage, which should be matched with the input of the instrument or the automatic control device behind the current transmitter.
3. Specifications of auxiliary power supply: In order to accurately detect the change of input current, and also to output DC signal that changes linearly with input current, it usually needs an auxiliary power supply to operate the most current transmitter. Usually, the most widely used is the AC 220V. You can also choose DC power, such as DC 24V and so on. It should be noted that there are some current transmitters that claim to require no auxiliary power, so-called "passive" current transmitters. For this type of current transmitter, it should be carefully selectd. The so-called "passive type" does not require a power supply, but the working power supply is provided by the meter behind the current transmitter output signal. It is "eat the instrument power supply behind the transmitter". Naturally increases the burden of collecting the instrument behind the transmitter. There is also a "passive type current transmitter" that uses the secondary current of the current transformer as the power source for the transmitter. The disadvantage of this type of transmitter is that when the load current is small, the current output of the current transformer is naturally small, and the energy supplied to the transmitter is also reduced. At this time, the current transmitter will generate a nonlinear error, thereby According to the error of the current signal transmission, this kind of transmitter also needs to be used with caution.
So,Pay attention to the above three issues when you select a current transmitter.