Transmitter module DH4-20
The standardized analog signal current value of 4 to 20mA two-wire loop is widely used in the transmission of data and the control of certain actuators that are easy to receive instructions in this standard. It has been used as the international standard for current telemetry in analog signals. In a two-wire current telemetry circuit, the operating power supply is in series in the loop with the reading device, including the sensor and any other resistance of the transmitting wire.
Main features:
◆ It is not easy to be affected by parasitic thermocouples and resistance voltage drop and temperature drift along the wire, and can be used very cheap and thinner wires;
◆ When the output resistance of the current source is large enough, the voltage in the wire loop induced by the magnetic field coupling will not have a significant impact, because the current caused by the interference source is very small, generally the use of twisted pair can reduce the interference;
Capacitive interference will lead to receiver resistance related error, for 4 ~ 20mA two-wire loop, receiver resistance is usually 250Ω (sampling Uout=1 ~ 5V) This resistance is not small enough to produce significant error, therefore, the wire length can be allowed longer than the voltage telemetry system; ◆ Each single reading device or recording device can be changed between different channels with different wire lengths, and no difference in accuracy is caused by different wire lengths;
◆ Using 4mA for zero level makes it easy to determine open circuit or sensor damage (0mA state).
◆ It is easy to add surge prevention and lightning protection devices in the two-line output, which is conducive to safety and explosion protection.
Application field:
DH4-20mA analog serial port module is a single-chip module product produced by Zhongke Ark Company using ST ASIC core chip to realize the two-wire current telemetry technology of passive AC isolation sensor (mutual induction principle). After rectifier filtering and I/V conversion, the input current signal of the passive AC isolation sensor outputs a DC voltage signal U2 which changes linearly with I1. U2 is used as the floating voltage control signal to control the module’s output current loop of 4 ~ 20mA. The module converts the passive AC isolation sensor signal into a proportional loop current sent by two connected lines, and the receiver detects the loop current by measuring the voltage drop at both ends of the known resistance RL (illustrated).
Technical parameters:
1. Rated loop current: DC4-20mA (static, full range adjustable);
2. Rated control terminal voltage: DC0-5V±10% (static, full range adjustable);
3. Rated operating voltage: +24V±20%;
4. Control input current: ≤100uA;
5. Power consumption: static 4mA, dynamic equivalent to loop current 20mA;
6. Nonlinear distortion: 0.1%FS;
7. Output current temperature drift: ≤50ppm/℃;
8. Static zero level: (4mA) Adjustment range: 4mA±25% (3mA-5mA);
9. Minimum working voltage: 15V;
10. Limit working voltage: ≤35V;
11. Output current protection: internal limit (TVS capacity: 24A, 20us);
12. Access protection: power reverse protection (need external 1N4007 diode);
13. Working temperature: -40℃-80℃;
14. Storage temperature: -50℃-100℃;