The copyright and authority for the interpretation of the products are reserved by MORNSUN

HK series

2013.10.09- A/3

Page 4 of4

Note:

1. Operation under minimum load will not damage the converter; However, they may not meet all specifications.

2. Max. Capacitive Load is tested at nominal input voltage and full load.

3. Unless otherwise noted, All specifications are measured at Ta=25

°C, humidity<75%, nominal input voltage and rated output load.

4. In this datasheet, all test methods are based on our corporate standards.

5. All characteristics are for listed models, and non-standard models may perform differently. Please contact our technical support for more detail.

6. Please contact our technical support for any specific requirement.

7. Specifications of this product are subject to changes without prior notice.

MORNSUN Science & Technology Co.,Ltd.

Address: No. 5, Kehui St. 1, Kehui development center, Science Ave., Guangzhou Science City, Luogang district, Guangzhou,P.R.China.

Tel: 86-20-38601850

Fax:86-20-38601272

E-mail: info@mornsun.cn

Http://www.mornsun-power.com

In the circuit of figure 4,

Sensor signal is converted into digital signals through the ADC, then sent to the current loop DAC and HART

modulator through MCU, form 4~20 mA signal output. Current loop DAC takes electricity from the PLC bus of output 4~20 mA, output 3.3 V and

2.5 V through the built-in voltage regulator, supply a small amount of power for MCU and HART modulator.

In the transmission of figure 4, there are ground electric potential differences between two-wire system instrument and PLC on the far side,

introducing the common mode interference. The disturbance causes the transmission error of 4~20 mA, and affects the normal communication

HART bus. If the common mode interference is too large (over the voltage range of the components in the common-mode), it may cause damage

in the internal instrument of two wire devices.

Signal transmission mode of isolated two-wire system

(Figure 5)

Due to the potential risks based on the different ground, you can isolate the MCU and the current loop DAC and HART modulator by digital

isolation. Current loop DAC and HART modulator is floating form. They make the high impedance formed to two ground potential between two-

wire instrument and PLC system, reduce the loop current between the ground wire, and electrical isolation between two devices, so as to eliminate

the hidden trouble of common mode interference.

The two-wire instrument goes without additional power supply port. The power supply takes power through the 4-20mA loop. After the isolation

mode,2.5V power of HART modulator is still formed from the built-in voltage regulator of loop DAC regulator, but the power supply for the 3.3V

MCU system is a difficult problem. A better solution is to connect witha voltage stabilizing diode in the 4-20mA circuit as shown in Figure 5. Then

you can use HK module of MORNSUN to isolated and output 3.3Vpower to the MCU power system. Using the HK module and digital isolation

circuit made by MORNSUN, you can realize the electrical isolation of two-wire instrument and PLC system .It avoids the measuring error of the

system and damaging equipment caused by ground potential, and it further enhances the reliability of the system.

trans duc er

ADC

MCU

3.3V

2.5V

H A R T m o d ula tor

volt age

regulstor

curr ent loop

DAC

tw o w ire in stru m e nt

～

～

～

4 -20mA

24V

PLC

Dig ital

iso lat ion

H K

D