1.Why RS-232 serial port is easy to be damaged?
Serial communication is upper machine and lower machine,or
communicationbetween PC and instrument. As there is a certain
distance between PC andinstrument,usually the distance is 5
meters,higher voltage will be inductive(inductivevoltage is
Proportional to the distance). The PC serial port or
instrumentserial port is made of ICs. Due to special workmanship of
IC, the voltage-withstandingvalue is low (usually less than 20V).
In case of thundering or strongelectric spark interference,the
inductive voltage will be rather high.Once the voltage is beyond
the max, withstanding voltage of the serialIC,the IC will be
punctuated and the serial port will be damaged. Thelonger the
communication cable,the higher damage rate. Many people thinkthat
serial port damage is caused by thunder which hit the machine.
Ifthis is correct, not only serial port will be damaged, but also
the humanbeing, house...
2.Theory and necessity of RS232 Surge Protector
With the appearance of serial port isolator protection,the portion
ofserial port that withstands high voltage is placed outside of the
hostmachineif serial protector is inserted in the port on host
machine,andthere is no physical connection in the circuits with the
host machine.Thereis only connection by light path. High voltage
will not be inductive becausethe connection portion with host
machine is short. Therefore, serial portcan be protected from
damage. Even though serial protector is damaged,theserial port on
host machine will be not damaged,repairing is simplified.
3.Advantages of RS232 Surge Protector
There is no direct connection between the circuit at the front
terminalwhich sustains high voltage and the circuit at the back
terminal whichconnects with host machine, the reliability of
protecting host machineis very good. Even though the communication
cable is very bad,the hostmachine is not threatening if only the
isolation voltage of the opticalcoupler is not surpassed.
4.Disadvantages of RS232 Surge Protector
As optical coupler is used by the serial port isolator to divide
the circuitinto two parts (front part and back part),each part is
powered by connectingthe pins on RS232. For serial communication
between instrument and hostmachine,the isolator is connected to the
host machine,the front circuitis powered by the instrument and the
back circuit is powered by the hostmachine. Therefore, one Isolator
protector is in tandem for one communicationcable and one terminal
of equipment can be protected. When two terminalsare in tandem to
the isolator,the middle part can not be powered,the circuitdoes not
work. Even there is external power supply, the signal will
bedistorted or delayed during the optical coupler transmission.
After thetwo distortions are superimposed or delayed,the baud rate
can not reach9600 BPS and the compatibility is lowered greatly.
Moreover, the wiringswith power supply will be superimposed and
interference the inductivevoltage, serial port isolator protector
will be damaged easily. When theIsolator protector is inserted host
machine, the instrument is not protected.When the Isolator
protector is inserted in the instrument, the host machineis not
protected. When the protector is inserted in the middle,
eitherinstrument or host machine can not be protected.
5.Characteristics of GL-RS232-1 RS232 Surge Protector
1). Sufficient size, reasonable wiring, sufficient safety space, no
wire-distributioninterference, the isolation voltage is up to the
optical coupler,2500Vcan be reached,Isolator protection is more
2). Equipped with reliable components,consumable parts such as
IN4148,TC7660with low voltage withstanding value and poor surge
immunity are not used.Crystal triode and FR107 parts are used for
better reliability. It iswell known that the voltage withstand of
common crystal triode can reach40V or above, which is 3 times of
TC7660,and the voltage withstand ofFR107 can reach 1000V,current
can reach 1A. 1N4148 can not compare withthem;
3). GL-RS232-1 RS232 Surge Protector is with multi
protectionfunctions. Due to the limit of space and size, many
serial port isolatorsare not equipped with self-protection part,so
it may be damaged by itself.GL-RS232-1 and GL-RS232-2 Serial
Protectors have sufficient space to arrangethe self-protection
parts. They can protection themselves while protectingothers.
4). Good compatibility. GL-RS232-1 RS232 Surge Protectoris powered
directly from TXD pin, it is fully compatible to 3-wire serialport
which is made of MAX202 and MAX232 ICs. Two-direction power
supplyis adopted, stability at low baud rate can be ensured.
5). Destructive testing at AC 100V,0.5 second is passed before
delivery.It can not be damaged easily in high strength EMI.
6). 2 years warranty.
6.Technical Specification of GL-RS232-1 RS232 Surge Protector
1). Connection:DB9 connector at the two sides;