| 摘要 |
PURPOSE To realize a simplified and low-cost device with the high-accuracy measurement by securing the sharing of the division calculation part between the pH measurement system and the temperature measurement system. CONSTITUTION:The signal corresponding to pH of the liquid to be measured is obtained in the form of output signal V1 of amplifier 1; and the temperature compensating signal is obtained in the form of output signal V3 of addition part 3 respectively. The inter-electrode potential Vi between glass electrode 8 and comparison electrode 9 is obtained in the form of output V1 of amplifier 1 having the impedance conversion and signal inversion functions. Both output signal -Vbe at the temperature detecting part and output signal Vk of constant power source 13 are used for the output of part 3, and then the coefficient is multiplied to these signals individually. Thus V3 is obtained through the multiplication. Temperature sensor transistor 10 is provided to the feedback circuit of operational amplifier 11, and current Ic is supplied to the collector from constant current source 12. Thus voltage -Vbe is obtained at the output end of amplifier 11. Signals V1 and V3 are applied to addition part 2, and signal V2 is delivered to be applied to division calculation part 6. At part 6 the calculation is carried out via change-over switch 14 and with use of signals V2 and V3 or output signals V4 and V5 of addition parts 4 and 5 each for the input. Thus display signal V6 of V6' is delivered to display part 7. |
