Abstract: An instrumentation device having a pulse output function for preventing breakage of a switching element even if a wrong wire is connected. A calculation unit includes: a positive power supply terminal; a negative power supply terminal; a signal terminal; a control circuit; an NPN-type transistor; a feedback circuit; a PTC thermistor; and an N-channel type MOSFET. The NPN-type transistor has a collector terminal connected to the positive power supply terminal, an emitter terminal connected to the negative power supply terminal, and a base terminal connected to the control circuit. The PTC thermistor is a resettable protection element, and is connected in series to the signal terminal. The N-channel type MOSFET has a drain terminal connected to the signal terminal through the PTC thermistor, a source terminal connected to the negative power supply terminal on a downstream side of the feedback circuit, and a gate terminal connected to the control circuit.

Abstract: An instrumentation device having a pulse output function for preventing breakage of a switching element even if a wrong wire is connected. A calculation unit includes: a positive power supply terminal; a negative power supply terminal; a signal terminal; a control circuit; an NPN-type transistor; a feedback circuit; a PTC thermistor; and an N-channel type MOSFET. The NPN-type transistor has a collector terminal connected to the positive power supply terminal, an emitter terminal connected to the negative power supply terminal, and a base terminal connected to the control circuit. The PTC thermistor is a resettable protection element, and is connected in series to the signal terminal. The N-channel type MOSFET has a drain terminal connected to the signal terminal through the PTC thermistor, a source terminal connected to the negative power supply terminal on a downstream side of the feedback circuit, and a gate terminal connected to the control circuit.

Abstract: A converter pulse width shaping circuit (6) according to the present invention is provided between a waveform shaping apparatus (4) and an erroneous output preventing apparatus (5) that are provided between a flow rate detecting portion (1) and a flow rate metering mechanism (3). When high frequency pulse signals of a frequency not lower than a predetermined value are successively input, the converter pulse width shaping circuit (6) combines those high frequency pulse signals to convert them to a low frequency pulse signal, which is then output to the erroneous output preventing apparatus (5) having a low-cut function. In the present invention, a vortex flow meter is made up of a converter (2) including the converter pulse width shaping circuit (6) described above.