To enable both types of a sensor having a built-in conversion circuit and a sensor having no built-in conversion circuit among various sensors produced commercially to be used, in order to able to compute, display and accumulate an analog physical quantity having an intrinsic physical unit, for unifying data management.

A data collecting system is provided, which includes: one or a plurality of sensors each having the built-in conversion circuit; one or a plurality of sensors having no built-in conversion circuit; one or a plurality of signal converters 18 each being connected with the sensor one-on-one and converting a sensor signal output by the sensor into a unified standard electric signal; an A/D converter 15; a PLC 14; a data storage means for executing a storing operation into a memory section so as to correlate with the maximum rated value of the sensor; an arithmetic means for computing the analog physical quantity of accumulated data; and a data displaying means for displaying a processed result of the data.