ZERO ADJUSTING METHOD FOR INTEGRATING A/D CONVERTER, LOAD CELL TYPE SCALE ZERO-ADJUSTED AT EACH POWER-ON

摘要

PROBLEM TO BE SOLVED: To quickly and easily make a zero adjustment by shortening the input integration time in the zero adjustment. ;SOLUTION: When the input voltage V_x of a measurement object is connected to an R via a SW₁, the output V₀ of an integrator is gradually lowered to reach 0V, the output of a comparator is changed from H to L, and a control device calculates the fixed time t_x (input integration time) from this time. In the zero adjustment of the integrator, the following equations are satisfied: V_max=-V_0min/t_x xRC, V_max'=-V_0min/t_x'xRC, t_x'=t_x/K, V_max'=V_max×K, where tx' is the input integration time smaller than the input integration t_x in an actual measurement, V_0min is the lower limit value of the output V₀, V_x is the voltage value when the output voltage XOR is V_0min at the expiration of the time t_x, V_max is the upper limit value of the voltage V₀, and V_max' is the upper limit value of V_x at the time t_x'. When the time t_x is shortened to 1/K, the voltage allowed to be inputted can be increased to K times, the number of counts should be merely increased to K times in the zero adjustment, and the zero adjustment can be made quickly and easily.;COPYRIGHT: (C)1997,JPO