A signal is a physical quantity that identifies a message, such as an electrical signal that can represent different messages through changes in amplitude, frequency, and phase. There are two types of electrical signals: analog and digital. A signal is a tool that carries a message and is a carrier of the message. In the process of using the instrument, the current signal, voltage signal and digital signal light will be used in a variety of forms, for the current signal, if the instrument has an independent working power supply, then the signal output it provides is an active signal, if the instrument itself does not have an independent power supply, the signal it provides is a passive signal. Instruments that use three-wire voltage signals and four-wire digital signals are active signals. Active Signal Acquisition: The acquisition of instrumentation active signal is more convenient, the first should be connected to the power supply of the signal source equipment (generally speaking, there are two types of three-wire system and four-wire system) to let the backup work normally, and the second will be the positive end and negative end of the input interface of the acquisition equipment respectively with the positive end and negative end of the signal source equipment corresponding to the connection line. Acquisition of passive signals: The first step of the acquisition of active and passive signals of instrumentation requires a DC 24V power supply (because the two-wire instrument that provides passive signals does not have a separate working power supply, when it needs to output 4-20mA signal, its working voltage needs to be provided by external equipment.) This DC24V power supply can be an independent power supply, or it can be provided by the power distribution function of passive signal acquisition equipment); The second step is to produce a correct loop between the two-wire instrumentation, DC24V power supply and passive signal acquisition equipment: the positive pole of the DC24V power supply is connected to the positive pole of the 4-20mA output of the two-wire instrument, the negative pole of the 4-20mA output of the two-wire instrument is connected to the positive pole of the 4-20mA signal input end of the acquisition equipment, and the negative pole of the 4-20mA signal input terminal of the acquisition equipment is connected to the negative pole of the DC24V power supply, so that a complete loop is generated. If you have any questions about product consultation, product customization, agency, technical inquiry, quotation, etc., please contact Xingyi: 400-600-4496!