CHENZHU SPD for signal is mounted by DIN rail. It can be selected from informations below.

1.     type of the signal

According to the signal type， we can get the information of the signal voltage, so as to determine Uc.

For example, normally,

AI，AO： 24V，

DI，DO： 24V，

RS485， TC：5V，

RS232：12V

RTD：5V.

2.    Rated current IL

Since SPD for signal is normally installed in series, operating current will go through SPD. If operating current is bigger than IL of SPD, SPD will be damaged. Normally IL will be big enough. For 3-wire, 4-wire transmitters and DO signals which have higher power consumption, IL need to be checked.

3.  Number of wires to be protected

Select 2 wires, 3 wires, 4 wires accordingly.

4.  Is intrinsically safe explosion-proof required? 

Yes——select intrinsically safe SPD; 

No——select non intrinsic safety SPD.