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What are the criteria for a quality digital caliper ?
    Digital caliper is a versatile measuring tool. It's widely used in workshops or DIY field. What are the criteria for a quality digital caliper ? How to judge its quality ? Not every one knows it. Now, follow the following criteria, you'll be able to distinguish between a high-end digital caliper and a low-end digital caliper.

1) The accuracy of electronic module
    The accuracy of electronic digital caliper depends on the accurancy of mechanical parts , electronic module and stator strip sensor. Manufacturing electronic module needs high technology and special precision equipment. There are several manufacturers of electronic modules in China.But only one manufacturer can make electroni module with high accuracy. All low-end electronic digital calipers use electronic modules with low accuracy. How can we know the accuracy of electronic module ? Just check digital caliper with a set of 9-piece gauge blocks with a step of 0.5mm, such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5mm or with a module master (from 5mm to 10mm, the correct way is to set zero while the measuring faces of the digital caliper's lower jaws contact the Module Master at 5mm and then begin to measure in order to avoid the errors of the stator, the measured value should be 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5mm which corresponds to 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10mm of the Module Master), you can easily find out the accuracy of the module. If the accuracy is=0.01mm, it shows the module's accuracy is high. If the accuracy is =0.02mm, it shows the module's accuracy is low. Anyi's specially designed Module Master can check modules fast and easily(see the image below).

2) The accuracy of outside measurement
    Check the inside measurement of a digital caliper with gauge block set or step gauge. If the accuracy is =0.02mm (0-100mm) and =0.03mm (>100-300mm), it shows the accuracy accords with the limit of National Standard.

3) The clearance of closed measuring faces
    Close the measuring faces, hold the caliper between your eyes and the light. Align the light, measuring faces and your eyes. If you can see light from the closed measuring faces, it shows the measuring faces are not lapped well. If you can't see any light from the closed measuring faces, its shows the measuring faces are well lapped . All quality digital calipers have well lapped measuring faces.

4) The kind of stator strip sensor
    All low-end digital calipers use stator strip sensor made of copper plating glass-epoxy laminate. Some high-end digital calipers use stator strip sensor made of indium coated glass. Such glass sensor is more reliable than copper plating glass-epoxy laminate sensor and has smaller coefficient of thermal expansion than the latter.

5) The parallelism of the bar
    Close the jaws and lock the slide slightly with the lock screw, then pull the slide toward the end and see if the slide can move through the whole bar. If the slide can move to the end, it shows the parallelism of the bar is good.If the slide can move only some distance away from the origin, it shows the parallelism of the bar is poor. In this way, you can check the middle or the end of the bar and see if its parellelism is good or not. The parallelism can affect the accuracy of the digital caliper.

    The five criteria above are enough for you to assess a digital caliper correctly. Other factors are not so important.

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