Load Cell Systems offers a couple of powerful, yet low cost, options for multi-channel load cell transmitters. After extensive research and testing, we have chosen to provide our customers with the Laumas (made in Italy) models TLB4 and TLM8 instruments to fill this product requirement. Below we will explain how our years of experience has led us to this decision.
There are a few options when it comes to a single device that can be connected to more than one load cell and have the ability to access the individual load cell’s readings. Traditionally these products were designed more for laboratory use than industrial or commercial applications. The extreme cost of these multi-channel strain gage load cell transmitters limited their use and typically had to be used with their own proprietary logging software. Due to the level of difficulty to use and higher costs, OEM and end-users would typically have to buy individual load cell electronics for each load cell they needed to collect data from.
This is why we chose the TLB4 and TLM8 models. Two main uses for these multiple load cell devices make them a very popular solution to many force measurement and weighing operations. One of the main uses is tank, hopper, and silo weighing applications; the other is transmitting individual load cell’s readings to another device such as a PLC or PC.
Tank Weighing Applications:
Using one of these load cell transmitters allows a connection from each of the load cells supporting a tank directly to one of these devices. This ability eliminates the need for a load cell junction box. The benefit of this is that there is one less component to purchase, install, calibrate, and have the potential for failure. Like a load cell j-box, the Laumas TLB4 and TLM8 offers digital equalization which averages the incoming load cell signals and displays, and transmits the total load on the scale. Digital equalization is much faster and easier to setup than a standard analog junction box and prevents drifting over time and with large temperature swings. In addition, both models allow the operator to view each of the connected load cell’s individual readings. This ability aids in distributing the load evenly on all load cells during installation, and is useful for troubleshooting the system while in use. These transmitters also have real-time diagnostics which will notify the operator if an imbalance is present between the individual load cell readings (if weighing a self-leveling product in a vessel). This can be a sign that there is mechanical binding or possibly a load cell failing.
Monitoring Multiple Load Cells:
Each of the load cell transmitters TLB4 (4-channels) or the TLM8 (8-channels) can be used to connect from 1 to 4 or 8 load cells. This is common for industrial or commercial applications such as multi-station filling machines, or medical devices utilizing multiple load cells. The load cell’s raw A/D unfiltered data (this data is then scaled in the connected device / PLC in to any weight units required) is transmitted via Modbus RTU or one of many available Fieldbus or Ethernet communication protocols. The solution offered by other companies often requires the use of their software with little or no possibility to output the transducer’s readings to another device. The TLB4 and TLM8 models are made to do exactly that. There is no need for a custom software package to use these devices. They output data in various popular industrial protocols, which allows the user to use existing or off-the-shelf PLCs or PCs to integrate with their pre-existing network.
Communication Protocols:
Below is a list of available communication options.
- CANopen
- DeviceNet
- CC-LINK
- Profibus DP
- Modbus/TCP
- Ethernet TCP/IP viewable by internet web browser on local network and worldwide web
- Ethernet IP
- Profinet IO
- 2x PROFINET IO ports
- 2x POWERLINK ports
- 2x SERCOS III ports
Selecting a Multi-Channel Transmitter Conclusion:
For the ease of use with existing networks, price point, and excellent technical support, the TLB4 and TLM8 manufactured by Laumas and distributed by Load Cell Systems is a simple and logical choice.