What are the factors that cause fluctuations in the division value of the balance, and how to adjust it? On the scale scale of the measuring instrument, the value of the measured size represented by the smallest grid is called the division value. As a precision measuring instrument, the balance often encounters fluctuations in the division value of the balance during actual use. Then, what are the factors that cause the fluctuation of the scale division value, and how to adjust it? The following is a detailed introduction by professionals.
Professionals pointed out that the factors and adjustment methods that cause the fluctuation of the scale division value are as follows :
1. The blade is normal, but the index value of no-load and full-load is quite different. The main reason for this situation is that the "eat" and "off" lines of the three knives are too large. The so-called "eating" and "leaving" lines refer to the plane relationship of the three blades. If the fulcrum blade is below the line connecting the two load-bearing blades, it is an eating line; if the fulcrum blade is above the line connecting the two load-bearing blades, it is off-line. . When the line is too large, the resultant center of gravity of the beam system is lower than that of the beam without load. Therefore, the division value under the load state will become larger. And the greater the offline, the greater the difference between the balance empty and the full load division value. To check the eating line of the three blades, in addition to using some special measuring tools or observing with the naked eye, it can also be checked by measuring and comparing the graduation values of the balance and full load according to the above principles. In order to ensure the measurement accuracy, the vertical position of the fulcrum knife and the load-bearing knife of the balance shall strive to minimize the off-line degree of the blades of the three knives. The specific method is as follows:
1. For a balance with an adjusting ball on the back of the fulcrum blade, the adjustment ball can be used to adjust the height of the fulcrum blade (that is, take off-line). When adjusting, you only need to loosen the screws on both sides slightly, insert the stick into the hole of the spherical nut, and turn it clockwise. At this time, the nut descends, and the screw moves upward. Retraction, which can reduce the extent of the blade eating the thread. Otherwise, the blade can be adjusted offline. After adjustment, the screws on both sides should be tightened to prevent the knife seat from loosening.
2. The fulcrum knife of some balances is designed to be fixed, and there is no lifting and lowering adjustment device. This kind of balance only relies on moving the load-bearing knife seat to adjust eating and offline. The form of load-bearing tool holders is also not the same. Some are adjusted by slightly pushing and pushing the inclined plane or the thickness of the pad clamp metal sheet, but most of them are adjusted by setting three screws under the knife seat to adjust the lifting of the knife. If you want to raise the knife, you must first loosen the screws on both sides, and then tighten the screw in the middle, so that the knife seat and the knife will rise, and then tighten the screws on both sides after adjustment, but the screw force on both sides should be equal , so as to avoid the phenomenon of unequal arms. Conversely, if you want the load-bearing knife to descend, you can also loosen the middle screw first, and then tighten the screws on both sides.
2. Due to long-term use, the blade wear becomes blunt, or the blade is cracked due to careless use, so it can only be solved by re-sharpening or changing the blade.
3. The blade is normal, and the indexing value is the same at no-load and full-load. But the value is too large or too small. At this time, it can be adjusted by changing the position of the center of gravity. If the scale value is too large, the center of gravity will be moved upwards, and if the scale value is too small, then move down. If the center of gravity moves to the lowest position, but the division value still does not meet the requirements, you can fix a small piece of lead at the appropriate position of the pointer to lower the center of gravity of the beam, otherwise you can file off a small part of the lead, to raise the center of gravity. If still not up to requirement, the center of gravity thallium of appropriate weight can also be replaced to adjust. However, it should be noted that since the position of the center of gravity of the beam is closely related to the stability of the balance, the above adjustments must be made without affecting the stability. That is to say, the center of gravity of the beam is required to be always below the fulcrum.
