| 摘要 |
PURPOSE:To realize an A/D converter having a prescribed conversion accuracy with a larger converting range inexpensively by providing an A/D converter converting an input signal of a large level and an A/D converter converting an input signal of a small level and using the both so as to apply simultaneous conversion to the input signal. CONSTITUTION:The converting range of an A/D converter 4 for red blood corpuscle of a blood corpuscle is selected to a larger range where no overflow takes place even with a scattered light pulse input by a maximum red blood corpuscle and the A/D converter 4 receives an A/D start signal from a peak detection and A/D conversion timing generating circuit 2 to start the converting operation and returns an A/D end signal at the end of conversion. The converting range of an A/D converter 5 for blood platelet is selected to a small range where the A/D converter 5 does not overflow even with a scattered light pulse input due to a maximum blood platelet and the converter 5 receives an A/D start signal from the circuit 2 to start the conversion and returns the A/D end signal at the end of conversion. The converter 5 outputs an overflow signal when the input signal is too excessive. A CPU and display circuit 6 fetches the inverted output of the converters 4, 5 and the overflow signal and use a discrimination signal indicating a blood corpuscle or a blood platelet so as to select an output of either the converter 4 or 5 as the A/D conversion value.
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