3. Working principle of Electronic Weight Scale
Electronic weight scale are equipped with electronic measuring modules. The electronic weighing machines operate based on the following principle: the force exerted by the load situated on the balance pan is transmitted to the load cell (one or more) which in turn emits an electric signal whose intensity is proportional with the force. The electrical signal is picked up by the electronic balance block, processed, amplified and transmitted to a digital display system (digital mass indicator), the result representing the weight of the mass located on the load pan. A very common solution is to use strain gauges (strain-sensitive transducers). These are generally used for commercial weighing devices with low resolution. The strain gauges are wired as a Wheatstone-bridge to balance for temperature changes .When the pan is not loaded by any object all four resistors are the same and the input of the amplifier is zero. When an object is placed on the pan R4 and R1 are compacted and their resistance decreasing, R2 and R3 are strained and their resistance is increasing. This becauses a voltage difference at the input of the amplifier, proportional to the weight of the object. The strain gauges are wired as a Wheatstone-bridge to compensate for temperature changes .
1 : Spring body
2 : Weighing pan
3 : Mounting plate (housing)
4 : Placing and wiring of the strain gauges (R3 and R4 can also be placed on the under side of the beam)
The advantages of electronic/digital weight scale are the plain fact that digital scales are considerably effortless to read. Besides, electronic weight scale will give more accuracy of reading value. Here are some disadvantages to electronic/digital scales, most likely the very regular one being incorrect readings. Several people have complained that when they stand on the scale at one spot and obtain a reading and when they get back after few seconds they get a different reading altogether. Normally, digital scales are good if just anyone make use of it since the mechanism could become worn out after regular use. This instrument need to calibrate after years to get better accuracy.