Shanghai Chenzhu Instrument CO., LTD.
Shanghai Chenzhu Instrument CO., LTD.

Electronic devices are always threatened by power surges and transients caused by power failures or nearby lightning strikes.

Signal SPD surge protection device is born to protect electronic devices in automatic control systems.

The surge protection equipment can provide surge protection for field equipments such as sensors, transmitters, flow meters, solenoid valves, thermocouples, thermal resistance, devices with RS485 or RS232 interface and for I/O interfaces such as Al, AO, Dl, DO, Tl, Pl in PLC, DCS, FGS, ESD control systems.

Signal data surge protector is widely used in petrochemical, gas, environmental protection and new energy industries. 

Chenzhu also provides signal surge arrester equipment in intrinsical safety circuits that meet the same design and structural standards as intrinsic safety equipment, which requires certification and approval of them.

FAQ of Signal SPD


How do I choose a signal SPD?


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,



2. Rated current IL

Since SPD for signal is normally installed in range, 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 carrier current 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.


How to judge if SPD is functional?


SPD protected the devices by discharging current to the ground. One-time strike will not damage SPD unless SPD is chosen incorrectly.

Power supply SPD is equipped with disconnector. If SPD fails, it will indicate through the indication window. SPD disconnector will not trip when it discharges lightning current. It is used to avoid fire hazardous caused by continuous fault current flowing through SPD when SPD is degraded.

For signal SPD, the risk of fire is small, so it is not required to set a disconnector. Normally, special lightning protection testing devices need to be used for off-line tests. Nowadays, with the technology development, the status indication function of signal SPD is becoming popular, so it’s also possible to judge by status indication.

we will meet your various needs
We have over 24 years experience in design and manufacturer of Automation Safety Interface Products.
Contact Us