circuit protection of rs485,232 telecom communication interface-九游会下载

brief introduction of ptc thermistor for circuit protection:

mz31 series mz9,mz6 type ptc thermistor are circuit protection component used in rs485,232 communication interface evolved out of the program-controlled 

security unit used for spc exchanges.this ptc tandem connection in rs485,232 communication interface, which can prevent damage to interface of 

telecommunication line effectively caused by importing 220 v electric supply due to accident broken or man-made damage, can also reduce influence to the 

interface of communication lines caused by lightning induction.this product has features of small steady resistance,low rated current, high voltage 

endurance capability and fast response etc., is economy applicable circuit protection choice of rs485,232 communication interface.

product application of ptc thermistor for circuit protection:

rs485,232communication interface protection 

working principle:

automatic meter reading is becoming increasingly popular in electronic power meters, this technology provides a communications port to the power meter, 

allowing it to be read electronically in a remote way. rs-485 is a simple, cheap, reliable communications specification that is well suitable for 

automatic meter reading. the ptc thermistor provides overvoltage protection in the circuit.for example if one of the rs-485 wires gets shorted to the 

main power line (eg, 220/380v), dxm’s ptc thermistor is specially designed for rs-485 interface protection. 

as indicated in fig 2 as below,when circuit is in the normal state, the current through ptc thermistor is lower than the rated current and ptc thermistor

is in the normal state with small resistance value,which will not affect the normal operation of the protected circuit such as primary and secondary 

loops of the voltage transformer.in case of some trouble in the circuit and the current is bigger than the rated current,the ptc will become hot quicklyand 

present high resistance value, which sets the circuit relatively “off” to protect the circuit from damage.after the trouble is removed,ptc thermistor

will automatically restore its low resistance state and the circuit will resume normal operation.

advantages:

1.small steady resistance ;

2.low rated current;

3.high voltage endurance capability;

4.fast response；

5.economy applicable circuit protection choice of 485 communication interface;

dimension(unit: mm):

marking of part number: 

1.series:ptc thermistor for circuit protection,overvoltage protection,overload protection

2.type:1-disc,2-encased,3-pin form-coating,4-pin form non-coating,5-smd

3.type:a-general, b-compount, c-moduie

4.chip size: 8-φ8mm          9-φ9mm         11-φ11mm      

5.curie temperature: f-50℃       h-75℃       n-100℃   p-120℃     k-125℃

6.r25 resistance: 6r0-6ω     6r5-6.5ω      70r-70ω      121-120ω 

7.resistance tolerance: k /-10%        m /-20%         h /-25%         n /-30%

8.greatly voltage:250-250v         265-265v

9.wire shape: s-straight, a-axis formed, u-in-formed

specification&part no.: