Abstract: An analog input device including a scanning circuit including a first insulation transformer insulating an analog signal inputted from a thermocouple, a power supply section charging a test voltage used for disconnection detection of the thermocouple, a second insulation transformer in which the scanning circuit and the power supply section are connected in parallel, and a control circuit for outputting a pulse signal to be inputted to the second insulation transformer. The second insulation transformer insulates and transfers a drive pulse for switching the scanning circuit and a power supply pulse for feeding power to the power supply section. The control circuit carries out a timing control so that the drive pulse and the power supply pulse are not outputted at the same time. Accordingly, an insulation transformer for application of a test voltage is not required, and thus the total number of the components is reduced to a great extent and reductions in costs and size thereof are realized.

Abstract: An analog input device according to the present invention includes a scanning circuit (3) including a first insulation transformer (T1) for insulating an analog signal inputted from a thermocouple (10), a power supply section (2) for charging a test voltage used for disconnection detection of the thermocouple (10), a second insulation transformer (T2) in which the scanning circuit (3) and the power supply section (2) are connected in parallel, and a control circuit (8) for outputting a pulse signal to be inputted to the second insulation transformer (T2). In the analog input device, the second insulation transformer (T2) insulates and transfers a drive pulse (41) for switching the scanning circuit (3) and a power supply pulse (42) for feeding power to the power supply section (2). The control circuit (8) carries out a timing control so that the drive pulse (41) and the power supply pulse (42) are not outputted at the same time.