PH meter siv chav tsev nug cov lus nug hauv qab no: PH meter yuav tsum tau kho peb lub ntsiab lus, thiab 2 ntsiab lus tsis txaus. Nrog rau kev kho los ntawm 7.004.01, yog qhov thib peb taw tes yog siv 9.21 buffer lossis lwm yam buffers xws li 10.01, 9.18, 12.46, 1.68, thiab lwm yam? Yuav ua li cas