Weigh Belt Scales - The Nuclear Approach

"Up until the mid 1960's, the only available methods for making continuous weight measurements were through the use of mechanical and electro-mechanical weigh scales. It was during this time period that a new concept in weighing was introduced. It was known and is still known as the nuclear belt weigh scale.During the early days of its appearance in the market place, many things were learned about its advantages and disadvantages for weighing various materials. As with many new devices, it had to go through a ""wringing out stage"" before it became accepted by the weighing industry. Even today, even though it is a proven device, there are skeptics who believe the nuclear belt weigh scale will not survive. Let me assure you, it is here to stay.. 'PRINCIPLE OF MEASUREMENTThe nuclear belt weigh scale consists of a ""C"" Frame assembly which houses the radioactive source (Cesiwn 137) and the radiation detector (Ionization chamber). The ""C"" Frame assembly is put in place around the conveyor belt as shown in Figure 1. The radiation source emits a fan shaped beam of radiation which covers the full width of the material being conveyed on the belt. Radiation which has passed through the material on the belt is detected by the ionization chamber which is located in the lower arm of the ""C"" Frame assembly. The ionization chamber changes the radiation energy into an electrical signal which is related to pounds per foot belt loading. This signal is transmitted to a highly stable amplifier which combines the pounds per foot signal with a belt travel signal from a digital tachometer which allowed the scale user to be able to monitor total mass being conveyed. Many so-called conventional type scales use belt speed rather than travel to obtain mass per unit time, and then integrate the signal to obtain their weight signal. This unnecessary step tends to erode the overall accuracy of the weighing system."