Signal isolator is to input single or dual current or voltage signal, transmit output isolated single or dual linear current or voltage signal, and improve the electrical isolation performance between input, output and power supply. The signal isolator adopts advanced digital technology and has excellent performance in suppressing high and low frequency interference signals. Even in high-power frequency conversion control systems, it can still be reliably applied. Internal digital calibration, zero point and full-scale potential are used. Automatic, dynamic calibration zero, automatic compensation of temperature drift and many other advanced technologies. The application of this series of technologies ensures the stability and reliability of products. The above technologies lead the international advanced level.
The signal isolator can be used together with the unit combination meter and DCS, PLC, DCS, MCu, single-chip acquisition card and other systems, and has been widely used in major projects in oil fields, petrochemicals, manufacturing, power, metallurgy and other industries. First, protect the lower level control loop.
Second, weaken the impact of environmental noise on the test circuit.
Third, to suppress the common ground, inverter, solenoid valve and unknown pulse interference on the equipment; at the same time the lower-level equipment with pressure limiting, flow function is the transmitter, meter, inverter, solenoid valve PLC/DCS input and output and communication The loyal protection of the interface. The DIN series rail structure is easy to install and can effectively isolate the potential between the input, output and power supply and ground. Can overcome the inverter noise and various high and low frequency pulsation interference. Need to be equipped with an independent 20~35VDC DC power supply. The advantage of this method is high isolation transmission accuracy; power supply, input, output completely isolated, multi-channel system power supply without isolation, can guarantee high anti-interference performance, the input signal can be converted to other types of models. The three main factors to resolve interferences are interference sources, sensitive sources, and coupling paths. There is no one of these three elements, and electromagnetic compatibility problems will not exist. Therefore we must start with these three elements. To find the most convenient solution, the general sources of interference and sensitive sources can not be resolved, usually from the coupling path to find ways, but also the most commonly used method. Such as adding shielding, filtering and other means. The treatment of circulation is the most common and most troublesome.
(1) The first method: All the field devices are not grounded, so that all process loops have only one grounding point and cannot form a loop. This method seems simple. However, it is often difficult to achieve in practical applications, because some equipment requires grounding to ensure measurement accuracy or personal safety, and some equipment may form new grounding points due to long-term corrosion and wear or weather influences.
(2) The second method: make the potentials of the two grounding points the same (as shown in Fig. 1, V1 = V2), but since the resistance of grounding is influenced by many factors such as geological conditions and climate change, this method is actually In practice, it cannot be done completely.
(3) The third method: The signal isolator is used in each process link to disconnect the process loop without affecting the normal transmission of the process signal, thereby thoroughly solving the problems of the ground loop. The superiority is in each process loop. Use signal isolation methods such as DCS or PLC, isolated clamps, or field-isolated transmitters (some devices can do this) or signal isolators. In comparison, using signal isolators has the following advantages:
In most cases, the use of signal isolator + non-isolated clips is cheaper than the use of isolated clips. The signal isolator is superior to isolation clips in isolation, immunity to electromagnetic interference, etc. The signal isolator is flexible in application and it It also has functions such as signal conversion, signal distribution and interface conversion, etc. It is more convenient to use. The signal isolator usually has a single channel, dual channels, and channels completely independent of each other, which makes configuration and routine maintenance of the system more convenient. Principle and application of signal isolator In the industrial production process, a variety of instruments and meters are used in the monitoring and control of the generation process, and various signals are generated: a weak millivolt small signal and several tens of volts. Large signals, even strong signals up to several kilovolts and several hundred amps; both dc low-frequency signals and high-frequency or pulse spikes; these signals are transmitted and transported to each other, so how to ensure these signals , especially if the analog signal is not distorted in the transmission process, it will become the system debugging. The problem must be solved. Specifically, the process control can only be guaranteed to be safe and reliable if the transmission of analog signals between the control device and sensors and actuators distributed in the field is trouble-free and undistorted. In particular, low-power analog signals are affected by various external interference signals when they are transmitted in a disturbing industrial environment, and they require a reliable transmission channel. Daily work experience shows that due to equipment requirements, it is necessary to handle and transmit analog signals with care. The measurement and control parameters transmitted between the field and the control layer in the form of analog signals are often in a relatively harsh industrial environment in transmission engineering and may cause distortion of these signals. Precautions
1 Pay attention to the auxiliary power supply information on the product label. The auxiliary power supply level and polarity of the transmitter cannot be connected wrongly, otherwise the transmitter will be damaged.
2 Positive output can only be achieved when the current direction is in the same direction as the arrow marked on the product housing;
3 The temperature of the primary busbar should not exceed 60°C. When the current busbar fills the primary threading hole, the best measurement accuracy is obtained.
4 There is no lightning protection circuit installed in the transmitter of this series. When the input and output feeders of the transmitter are exposed to outdoor harsh climate environment, lightning protection measures should be taken.
5 The transmitter is of an integrated structure and cannot be disassembled, and collisions and drops should be avoided at the same time;
6 Do not damage or modify the product's label, logo, do not disassemble or modify the transmitter, or the company will no longer provide "three guarantees" (replacement, return, repair) service for the product.
7 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, the final power amplifier tube (magnetic compensation type) will be damaged. Under normal circumstances, the duration of the 2 times overload current should not exceed 1 minute.
8 The voltage sensor must be connected in series with a current limiting resistor R1 according to the product description so that the primary side can obtain the rated current. Under normal circumstances, the duration of 2 times overvoltage should not exceed 1 minute.
9 The best accuracy of the current and voltage sensors is obtained under the condition of the primary side rated value, 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 rated value of the voltage sensor The current limiting resistor should be readjusted. When the measured current is less than 1â„2 of the nominal value, multiple turns can be used for best accuracy.
10 The sensor with insulation resistance of 3KV can work normally in 1KV and below AC systems and 1.5KV and below DC systems. Pay attention not to use overpressure.
11 When used on devices that require good dynamic characteristics, it is best to use a single copper-aluminum busbar and match the hole diameter. Larger or smaller windings will affect the dynamic characteristics.
12 When used in a high-current DC system, due to a certain cause of the open circuit or failure of the power supply, the iron core has a large remanence, which is worth noting. Remanence affects accuracy. The method of demagnetization is to not increase the power supply, pass an AC in the primary side and gradually reduce its value.
13 The sensor's resistance to external magnetic field is: 5~10cm away from the sensor, a current exceeding 2 times the current value of the sensor, and the generated magnetic field interference can resist. When three-phase high-current wiring, the distance between phases should be greater than 5 ~ 10cm.
14 In order to operate the sensor in the best measurement state, the simple typical regulated power supply described in Figure 1-10 should be used.
15 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 the test overload capacity is exceeded, the overload current more than 2 times must not exceed 1 minute.
16 The temperature of the primary side busbar must not exceed 85°C. This is determined by the characteristics of the ABS engineering plastics. The user has special requirements and can choose high temperature plastics as the shell. \
17 The insulation performance of the voltage isolation of the signal is better, and the withstand voltage should be >2kV.
18 PT, CT output load is small, because the transmitter used PT, CT core section by the volume constraints are relatively small, so as the output load increases, its nonlinear will increase dramatically, the general PT output Current should be <1mA, CT output current should be <10mA (generally about 5mA), sampling resistance should be <200Ω.
The signal isolator can be used together with the unit combination meter and DCS, PLC, DCS, MCu, single-chip acquisition card and other systems, and has been widely used in major projects in oil fields, petrochemicals, manufacturing, power, metallurgy and other industries. First, protect the lower level control loop.
Second, weaken the impact of environmental noise on the test circuit.
Third, to suppress the common ground, inverter, solenoid valve and unknown pulse interference on the equipment; at the same time the lower-level equipment with pressure limiting, flow function is the transmitter, meter, inverter, solenoid valve PLC/DCS input and output and communication The loyal protection of the interface. The DIN series rail structure is easy to install and can effectively isolate the potential between the input, output and power supply and ground. Can overcome the inverter noise and various high and low frequency pulsation interference. Need to be equipped with an independent 20~35VDC DC power supply. The advantage of this method is high isolation transmission accuracy; power supply, input, output completely isolated, multi-channel system power supply without isolation, can guarantee high anti-interference performance, the input signal can be converted to other types of models. The three main factors to resolve interferences are interference sources, sensitive sources, and coupling paths. There is no one of these three elements, and electromagnetic compatibility problems will not exist. Therefore we must start with these three elements. To find the most convenient solution, the general sources of interference and sensitive sources can not be resolved, usually from the coupling path to find ways, but also the most commonly used method. Such as adding shielding, filtering and other means. The treatment of circulation is the most common and most troublesome.
(1) The first method: All the field devices are not grounded, so that all process loops have only one grounding point and cannot form a loop. This method seems simple. However, it is often difficult to achieve in practical applications, because some equipment requires grounding to ensure measurement accuracy or personal safety, and some equipment may form new grounding points due to long-term corrosion and wear or weather influences.
(2) The second method: make the potentials of the two grounding points the same (as shown in Fig. 1, V1 = V2), but since the resistance of grounding is influenced by many factors such as geological conditions and climate change, this method is actually In practice, it cannot be done completely.
(3) The third method: The signal isolator is used in each process link to disconnect the process loop without affecting the normal transmission of the process signal, thereby thoroughly solving the problems of the ground loop. The superiority is in each process loop. Use signal isolation methods such as DCS or PLC, isolated clamps, or field-isolated transmitters (some devices can do this) or signal isolators. In comparison, using signal isolators has the following advantages:
In most cases, the use of signal isolator + non-isolated clips is cheaper than the use of isolated clips. The signal isolator is superior to isolation clips in isolation, immunity to electromagnetic interference, etc. The signal isolator is flexible in application and it It also has functions such as signal conversion, signal distribution and interface conversion, etc. It is more convenient to use. The signal isolator usually has a single channel, dual channels, and channels completely independent of each other, which makes configuration and routine maintenance of the system more convenient. Principle and application of signal isolator In the industrial production process, a variety of instruments and meters are used in the monitoring and control of the generation process, and various signals are generated: a weak millivolt small signal and several tens of volts. Large signals, even strong signals up to several kilovolts and several hundred amps; both dc low-frequency signals and high-frequency or pulse spikes; these signals are transmitted and transported to each other, so how to ensure these signals , especially if the analog signal is not distorted in the transmission process, it will become the system debugging. The problem must be solved. Specifically, the process control can only be guaranteed to be safe and reliable if the transmission of analog signals between the control device and sensors and actuators distributed in the field is trouble-free and undistorted. In particular, low-power analog signals are affected by various external interference signals when they are transmitted in a disturbing industrial environment, and they require a reliable transmission channel. Daily work experience shows that due to equipment requirements, it is necessary to handle and transmit analog signals with care. The measurement and control parameters transmitted between the field and the control layer in the form of analog signals are often in a relatively harsh industrial environment in transmission engineering and may cause distortion of these signals. Precautions
1 Pay attention to the auxiliary power supply information on the product label. The auxiliary power supply level and polarity of the transmitter cannot be connected wrongly, otherwise the transmitter will be damaged.
2 Positive output can only be achieved when the current direction is in the same direction as the arrow marked on the product housing;
3 The temperature of the primary busbar should not exceed 60°C. When the current busbar fills the primary threading hole, the best measurement accuracy is obtained.
4 There is no lightning protection circuit installed in the transmitter of this series. When the input and output feeders of the transmitter are exposed to outdoor harsh climate environment, lightning protection measures should be taken.
5 The transmitter is of an integrated structure and cannot be disassembled, and collisions and drops should be avoided at the same time;
6 Do not damage or modify the product's label, logo, do not disassemble or modify the transmitter, or the company will no longer provide "three guarantees" (replacement, return, repair) service for the product.
7 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, the final power amplifier tube (magnetic compensation type) will be damaged. Under normal circumstances, the duration of the 2 times overload current should not exceed 1 minute.
8 The voltage sensor must be connected in series with a current limiting resistor R1 according to the product description so that the primary side can obtain the rated current. Under normal circumstances, the duration of 2 times overvoltage should not exceed 1 minute.
9 The best accuracy of the current and voltage sensors is obtained under the condition of the primary side rated value, 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 rated value of the voltage sensor The current limiting resistor should be readjusted. When the measured current is less than 1â„2 of the nominal value, multiple turns can be used for best accuracy.
10 The sensor with insulation resistance of 3KV can work normally in 1KV and below AC systems and 1.5KV and below DC systems. Pay attention not to use overpressure.
11 When used on devices that require good dynamic characteristics, it is best to use a single copper-aluminum busbar and match the hole diameter. Larger or smaller windings will affect the dynamic characteristics.
12 When used in a high-current DC system, due to a certain cause of the open circuit or failure of the power supply, the iron core has a large remanence, which is worth noting. Remanence affects accuracy. The method of demagnetization is to not increase the power supply, pass an AC in the primary side and gradually reduce its value.
13 The sensor's resistance to external magnetic field is: 5~10cm away from the sensor, a current exceeding 2 times the current value of the sensor, and the generated magnetic field interference can resist. When three-phase high-current wiring, the distance between phases should be greater than 5 ~ 10cm.
14 In order to operate the sensor in the best measurement state, the simple typical regulated power supply described in Figure 1-10 should be used.
15 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 the test overload capacity is exceeded, the overload current more than 2 times must not exceed 1 minute.
16 The temperature of the primary side busbar must not exceed 85°C. This is determined by the characteristics of the ABS engineering plastics. The user has special requirements and can choose high temperature plastics as the shell. \
17 The insulation performance of the voltage isolation of the signal is better, and the withstand voltage should be >2kV.
18 PT, CT output load is small, because the transmitter used PT, CT core section by the volume constraints are relatively small, so as the output load increases, its nonlinear will increase dramatically, the general PT output Current should be <1mA, CT output current should be <10mA (generally about 5mA), sampling resistance should be <200Ω.
KXT26I AC500A/4-20ma DC24V
AC current sensor
working environment
Ambient temperature
-25°C～+80°C
Storage temperature
-40°C to +115°C
Relative humidity
≤ 90%
Pressure conditions
Normal atmospheric pressure
Electrical parameters
Rated current range
AC500A
Nonlinearity of error
0.1%
The output voltage
@Ip=Ipn DC4-20ma
Measuring current range
AC1000A
Overload times
unlimited
working frequency
Frequency 20-5khz
Working power
20-30 ±5%V
Power consumption
≦5+Io ma
Insulation resistance
Insulation pressure
3kV@AC50hz1Min)
Offset current current temperature drift
@-40-85°C≦100ppm/°C
Output current temperature drift
@-40-85°C≦100ppm/°C
Zero current
@Ip=o4±0.2%ma
Linearity
@Ipo=0±Ipn≦0.2%FS
Response time
≦250ms
bandwidth
0-3Db AC20-5khz
Mechanical parameters
Aperture
45mm
Dimensions
120*101*34
Secondary terminal
High and low terminal wiring
Terminal length
shell
PBT flame retardant material
Potting
Epoxy Epoxy Adhesive
weight
420g
tolerance
±0.3mm
Offset current
@Ipo ≦±0.1ma
Magnetic offset current
@Ipo=±Ipn-0 ≦±0.1ma
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