How to Test a Load Cell with a Multimeter

Summary

This video provides a step-by-step guide on how to test the accuracy and functionality of load cells. It covers essential checks, including verifying resistance values and comparing them with the calibration certificate. The process involves using a multimeter to measure input and output resistances, and applying excitation voltage to check for millivolt signal accuracy. By following these tests, users can confirm whether the load cell is in good condition and whether its readings align with the manufacturer’s specifications. The video also includes tips on purchasing budget-friendly load cells.

Takeaways

• 😀 Ensure to have the low cell calibration certificate and wiring diagram before testing.
• 😀 Verify the output and input impedance along with cable color codes before starting the test.
• 😀 Always compare the measured values with the manufacturer's calibration certificate for accuracy.
• 😀 Use a multimeter to measure the resistance across the input and output wires of the low cell.
• 😀 The expected output resistance for a good low cell is around 350 ohms, with an example reading of 353 ohms.
• 😀 The input resistance of the low cell should be approximately 435 ohms, with an example reading of 439.7 ohms.
• 😀 To test low cell accuracy, measure the millivolt signal across the signal wires.
• 😀 An external voltage source, like a low cell controller, can be used to provide excitation voltage for the low cell.
• 😀 With no force applied, the millivolt reading should be zero, as stated in the calibration certificate.
• 😀 Apply a calibrated weight and compare the output voltage with the specified value to check the low cell's accuracy.
• 😀 After completing the tests, you can shop for budget-friendly low cells through the provided link in the description.

Q & A

What is the primary focus of this video?

The primary focus of the video is to demonstrate how to quickly and easily test a load cell to ensure it is functioning properly.

What should you have before starting the load cell test?

Before starting the load cell test, you should have the load cell's calibration certificate, the wiring diagram with cable color codes, and information about the output and input impedance.

How do you measure the output resistance of the load cell?

To measure the output resistance, connect the digital multimeter between the positive and negative signal wires of the load cell, as per the wiring diagram. The expected resistance value is typically around 350 ohms, and a reading close to this is acceptable.

What is the expected resistance value for the load cell's output?

The expected resistance value for the load cell's output is typically around 350 ohms, and a reading of 353 ohms, as shown in the video, is acceptable.

What wires are used to measure the input resistance of the load cell?

To measure the input resistance, you use the positive and negative excitation wires, which are typically red and black, respectively, according to the wiring diagram.

What resistance value should you expect when measuring the input resistance?

The input resistance should match the specification in the calibration certificate. For example, the expected value in the video was approximately 435 ohms, with a measured value of 439.7 ohms, which is acceptable.

How do you test the load cell for accuracy?

To test the load cell for accuracy, you will need a multimeter and a voltage source. The video uses a load cell controller as the external power supply to provide the excitation voltage, and the millivolt signal across the signal wires is measured to check if the values match the calibration certificate.

What should the millivolt signal read when no force is applied to the load cell?

When no force is applied to the load cell, the millivolt signal should read close to zero, as indicated in the calibration certificate.

What should you do after applying a calibrated weight to the load cell?

After applying a calibrated weight to the load cell, you should compare the measured millivolt output to the expected value in the calibration certificate. If the output matches, the load cell is functioning properly.

What is the purpose of the load cell controller in the accuracy test?

The load cell controller serves as an external power supply to provide the necessary excitation voltage to the load cell during the accuracy test. It is powered by a 220V AC source and supplies 10V DC to the load cell.