Protection of Weighbridges and Load Cells Against Sudden Overvoltage

Damage to weighing scales in facilities as a result of lightning impulses is a chronic problem. Especially the burning out of Loadcells (load cells) causes the scales to become disabled, leading to serious economic loss and disruption of work. Scale equipment, which is damaged as a result of sudden surge impulses and voltage fluctuations apart from lightning, poses a major problem especially for factories. As Yılkomer, we have taken dozens of scales under protection at this point, but we were applied to after 90% of them were damaged. With this article, we wanted to provide information for facilities to take precautions before loadcell and scale systems are damaged. Systems that generally weigh trucks and lorries have a critical importance in facilities and must be protected to prevent possible errors.

Loadcell Load cell protection is important.

Scale systems include sections such as Indicator, Loadcell, Junction Box, External Display, Traffic Lights, RFID Vehicle Reader, Card Reader, IP Camera, Main Computer, Communication Modules. All system equipment can malfunction in a possible lightning and sudden surge impulse. In a scale with analog load cells, the scale makes incorrect measurements until the load cell failure is determined. In scales with digital load cells, loadcell replacement is required in a possible impulse. Both situations can lead to serious problems. Your loadcells burn out when lightning strikes the lightning rod in your facility or a land area 2 km away from your facility.

Also, the same problem occurs in impulses coming through the supply. We can protect your scale systems by performing cascaded protection with Safetec Technology LV Surge Arrester systems within the scope of IEC 62305 Standard. Especially when products that protect all system elements by performing unlimited damping are installed by expert teams, it is out of the question to experience a similar failure again. What needs to be done is to protect Energy, Data, and Coaxial Lines by selecting products suitable for DC and AC voltage levels. Scales are fed from Energy Distribution Panels located at a short distance. A Type 1+2+3 damping module must definitely be used in this panel according to the status of being single-phase or three-phase. Regardless of where the scale is, a product with minimum 50 kA per Phase, 100 kA Earth Neutral Line protection against lightning impulse in 10/350ms curve should be selected. It is important to select 40 kA Protected products within the scope of 8/20 ms curve as well.

The part where load cells need to be protected is primarily energy panels.

Type 1+2+3 must be written on every cartridge on the product. The aim here is to reduce the Up voltage level from 1.5 to 0.4 levels in a single product. The related product should not be only varistor-based. As Iskra –Raycap technology offers, it should consist of Safetec features, that is, the parallel operation of 2 GDT 2 MOV circuits. Thus, long-term protection is provided and it can dampen an unlimited number of impulses within the product capacity.

Load Cells have a circuit called a Wheatstone bridge. When a voltage is applied to the bridge, the output voltage becomes a voltage proportional to the applied load. Thanks to this small voltage formed, the weight of the applied pressure is measured. Load cells have a total of 4 terminals, 2 inputs and 2 outputs. In some load cells, the total number of terminals can be 6. In 6-wire load cells, 2 more terminals are connected to the input terminals. These connected additional terminals are named +sense and -sense. Their purpose is to detect whether any breakage has occurred in the load cells. Since loadcells with a sensitive circuit structure have many elements on the bridge, damage can occur to circuit elements in a possible impulse, which disables the loadcell. It should be externally protected with Class D sensitive protection modules within the scope of supply voltage. Class D sensitive protection should be performed on the Loadcell line according to 5-12-24v level. Also, scale equipment should be connected to the scale ring line with a spark gap damper. Communication in scales should generally be done via RS485 communication portals. 9 or 25 pin communication modules should be used in these lines as well, and PC equipment should be protected with Class D protection.

As the Lightning Protection Center, we would like to take your scale systems under 100% protection. At this point, we will be pleased to eliminate both your economic and temporal losses by proposing products and applying them with our expert team.