Load Cell Test Methods 3 Years ago

It has happened in many cases that you have encountered this case during or after setting up the load cell that it seems that the load cell does not behave as you expected or does not show any response to force changes.

The question that will arise for an engineer is how should I ensure the health of the load cell used?

According to the knowledge and experience gained in this field, Pars Mega offers some simple solutions for load cell troubleshooting and at the end offers you a simple and very accurate proposal.

1- Checking the appearance of the load cell

The first step in the load cell test is to check the appearance of the load cell, in other words, the load cell must not be bent or deformed. Note that the basis of the work of the load cell is based on this bending, but the load cell must be in its normal state without any force on it, and another point is that even when under load, the force must be applied in a direction that the factory The manufacturer of the load cell has mentioned it.

2-Appearance test of the cable

In many cases, it can be seen that the cable of the load cell has been interrupted or crushed, or has been chewed by vermin, which is possible to find this problem by visual inspection. The recommendation of ParsMega company experts is to use strong and resistant pipes to keep the cable safe.

3-load cell ohms test

At the time of buying a load cell, you will be given a load cell specification sheet, which will help you when troubleshooting the load cell, one of the things that is mentioned in this sheet is a parameter called Terminal resistance, input and Terminal resistance, output, which are respectively The resistance of the load cell is in the excitation part and the output part.

An example of this sheet is shown in the following table:

Imagine that we want to test this same load cell in terms of ohms. First, we disconnect the load cell wires from the load cell transmitter. Or the signal we do should be 350 ohms.

4- Humidity testing

In the situation where the load cell is kept in an environment with high humidity, there is a possibility of moisture loss. To be sure of this, you need an ohmmeter capable of measuring ohms up to the range of 2000 megaohms.

To perform this test, first separate the wires of the load cell from the transmitter or display and connect them to each other. Connect one end of the ohmmeter to the wires of the load cell and the other end of the ohmmeter to the body of the load cell. Pay attention that your body should not touch the end of the ohmmeter. be connected If the ohmmeter shows a value less than 2000 megaohms, moisture has penetrated into your load cell or cable.

5- Measuring the load cell output voltage

This is a very reliable and accurate way to diagnose load cell problems.

In ParsMega transmitters, there is a parameter that is mentioned in the manual called input voltage, its unit is millivolts.

Here, it is necessary to give a brief explanation about this voltage. In the load cell information sheet, there is a parameter called output sensitivity, whose unit is mv/V.

An example is given below:

This parameter indicates how much voltage the load cell puts in the output for every volt that is given to it in the excitation section in the state where the maximum load is placed on it.

For example, the load cell that is at the top of its information sheet, in the state where the full load is on it, for each volt in Excitation, the value of mv/v2 appears in the output, assuming that the excitation voltage is 5 volts, this load cell is in the state where all A load is placed on it, it puts a value of 10 mV at the output.

In this way, you can get what voltage should be in the output for each kilogram of load with a simple proportional table.

Please note that this parameter is displayed in the program that ParsMega Company provides to its respected users.

Engineers are advised to include this parameter in the HMI program of their device so that troubleshooting can be done faster using this parameter when the device is set up remotely.

If you need any advice or more information, please contact ParsMega Company.