What are the precautions required for the overlap test method of resistance?

When conducting overlap testing, the following are some important precautions:

1. Surface treatment: Before overlapping, it is necessary to thoroughly clean the overlapping area to ensure that the welding area is free of oil stains, rust, and surface oxidation, which is crucial for ensuring good electrical contact.

2. Contact resistance: The contact resistance between the lap joint and the installation surface should not exceed 100 micro ohms to ensure effective electrical connection.

3. Direct overlap: Overlapping parts should generally not adopt indirect overlap form, but should be directly overlapped on the basic structure to reduce contact resistance.

4. Non metallic materials: Overlapping connections should not pass through non-metallic materials for compression and fixation to avoid an increase in resistance value.

5. Grounding wire laying: The shielding sleeve grounding wire can be laid through the pins of the plug socket or directly connected to the basic structure. If the resistance from the plug socket housing to the basic structure is not greater than 1000 micro ohms, it can be grounded through the plug socket housing.

6. Avoid co location: The bonding wires of electrical and electronic equipment casings should not be fixed to the same grounding point as the negative power line to prevent interference from current circuits.

7. Measurement method: When measuring the overlap resistance with an instrument, a suitable probe should be selected, such as a test piece, alligator clip, and test pen rod. The test piece is in surface contact, with an appropriate contact area and a flat contact surface, which is a good contact method.

8. Measurement stability: When using crocodile clips or pen sticks for measurement, the measurement data may be unstable due to insufficient contact. Therefore, test pieces should be used as much as possible for measurement to reduce measurement errors.

9. Measurement environment: The temperature and humidity, dust, powder, oil stains, and preservatives in the measurement environment can seriously affect the contact and measurement results of the measurement surface. Therefore, written regulations should be made for the measurement environment (temperature and humidity).

10. Selection of measuring instruments: It is very important to choose suitable testing instruments that can measure small resistance, such as micro ohmmeters, DC resistance testers, low resistance testers, milliohmmeters, etc.

11. Measurement technique: Use the four wire measurement method to measure, where the current and voltage electrodes are completely independent to improve measurement accuracy.

12. Safe operation: When conducting lap testing, safety must be taken into account, especially when opening the electrical control panel or performing other operations. It must be done after the lap is completed to avoid safety accidents.

Following these precautions can ensure the accuracy and safety of overlap testing.