Load Cell Summing Junction Box Setup and Adjustment

Brief introduction of weighing junction box:

The weighing junction box is a device commonly used to connect load cells and indicating instruments, data acquisition instruments and other equipment. It usually contains multiple terminals, which can convert, amplify, and filter the output signal of the load cell, and output the processed signal to devices such as indicating instruments or data acquisition instruments for data recording and analysis. The weighing junction box can not only effectively reduce the interference and error of the signal line, but also facilitate the wiring and maintenance of the signal line, thereby improving the stability and reliability of the weighing system.

It works as follows:

First, the load cell measures the weight of the object being weighed and converts the signal into an electrical signal. This electrical signal needs to be processed and converted through the weighing junction box before it can be received and processed by the controller or instrument.

In the Ningbo Saintbond intelligent weighing junction box, the electrical signal is processed by amplification, filtering, denoising and amplification to ensure the accuracy and stability of the signal, and then output to the controller or instrument. In some high-precision application scenarios, the weighing junction box can also perform linear compensation and temperature compensation to improve measurement accuracy.

In general, the function of the weighing junction box is to process the electrical signal of the load cell into a signal suitable for the controller or instrument to receive and process, and to provide some signal processing and compensation functions in the process.

What is the working principle of the junction box:

We usually use multiple load cells to measure the weight of an item. For example, a tank, silo or platform with 4 legs, with a load cell under each leg. Or the weighing platform can consist of a square plate with load cells located under each corner. The output values of the 4 load cells need to be averaged on site and a single representative load cell signal output sent to a display or signal transmitter, this is accomplished through the load cell summing junction box, sometimes referred to simply as for the junction box. However, it's not just an empty junction box where you connect load cell wires so you don't have to run 4 sets of cables to the control cabinet or display. It integrates the electronics required to average or sum the load cell outputs into a single representative output.

Due to the differences in the key materials of the load cells, the strain and the projectile body and the manufacturing process, the parameters of each load cell are inconsistent, mainly because the sensitivity is inconsistent. This inconsistency is commonly referred to as the angle difference. The proper term of the box is to connect the output signal of the load cell to the junction box first, and then send it to the instrument, adjust the angle difference by adjusting the potentiometer inside the junction box, and then make the sensitivity of each load cell close to the same, so as to ensure the balance of the whole scale body. balance.

Inside the junction box you will see the associated screw terminals marked on the PCB. Each connected load cell has an adjustment potentiometer. The potentiometer allows you to adjust the sensitivity of the 4 load cells to be equal so that they give the same output under the same load, resulting in more accurate readings than would otherwise be possible. In addition to combining the load cell signals, the junction box is used to distribute the required excitation voltage to each load cell. The load cell junction box also provides 8 channels to support systems with more load cells.

Since the Ningbo Saintbond intelligent load cell junction box can be installed on site, it is possible to have an explosion-proof enclosure for use in hazardous areas. They are also available with a moisture resistance rating of IP67.

Load Cell Summing Junction Box Setup and Adjustment:

Turn all potentiometers counterclockwise at least ten turns until all potentiometers are at end points (they will click when turned past end points)

Connect all load cells. Apply the excitation voltage. Mount the test weight on top of the load cell or place the weight on the corner of the platform and record the output reading. You can record the output in millivolts on the multimeter, or whatever the amp/readout meter indicates, like kilograms, etc.

Repeat this process for each load cell or corner. It does not matter if the output value is not calibrated at this stage, the important thing is to record the output value of each load cell and not change any potentiometers at this time.

Select the 4 that will have the lowest reading among the load cells and keep their potentiometers. It is recommended that you seal this potentiometer with some locking glue. Now place the test weight on the other load cell and adjust the potentiometer associated with that load cell clockwise until the output reads the same as that recorded by the load cell with the lowest reading.

Repeat step 2 on the remaining 4 load cells or corners, making sure that when the test weight is applied to each load cell, its potentiometer is adjusted until the output of the junction box matches that of the load cell mentioned in step 4 The output is the same. Seal all potentiometers with locking glue. All load cells are now normalized to contribute equally to the total output weight reading. On a floor scale you should be able to center the test weight and still get the same output value.

You now have all 4 load cells installed in the system. Remove all weights and set zero on indicator or amplifier. Using test weights, you can start calibrating your system. Set the amplifier or indicator output to read the correct weight of the test weight. It should only indicate the value of the test weight, not the weight of the system tank, hopper, etc. Recheck the zero and loaded weights, repeating with different weights up to the maximum weight the system is designed for. Next, remove all test weights. With the system unloaded, adjust the tare of the amplifier or monitor to provide zero output. Add test weights and confirm correct reading one last time.