Thorough purging of all four bearing seals on each universal joint can help alleviate the possibility of mixing incompatible greases. U-joint cross, broken at a bearing surface. U-joints seldom break off at the bearing surface. It takes a very large shock load to cause this type of failure. It is also very difficult to inspect for this type of failure because they, many times, start as a small crack and progress into a complete failure some time further âdown the roadâ.
A quantity called the slew rate, which is the rate of change of gradient amplitude is usually quoted in evaluating gradient performance and potential physiological effects (e.g. a maximum slew rate of 200 Tm-1s-1).
With a step function change in Vin, greater than 350mV for this circuit, all the IS1 current is steered to one side of the input transistor pair and that current charges (or discharges) the Miller compensation capacitor, C1. The output slew rate (SR) is the rate at which IS1 charges C1, equal to IS1/C1.There are variations, of course. Op amps with slew-enhancement add circuitry to detect this overdriven condition and enlist additional current sources to charge C1 faster but they still have a limited slew rate.he voltage to slew an input stage (350mV for this design) varies from approximately 100mV to 1V or more, depending on the op amp. While the output is slewing it canât respond to incremental changes in the input. The input stage is overdriven and the output rate-of-change is maxed out.