The invention discloses a
system and a method for automatically testing an analog module with a settable input / output (I / O) channel in a
programmable logic controller (PLC). The
system comprises an upper control computer, a programmable
direct current signal source, a digital
multimeter, a channel and
voltage /
current mode switching control plate and a
communication interface, wherein the upper control computer sets a testing parameter, issues an instruction to realize output or measurement, receives a test result and makes judgment according to the result; the programmable
direct current signal source receives the instruction and the parameter to set the output as a
voltage or
current mode, sets and outputs a
voltage / current
signal to an input channel; the digital
multimeter receives the instruction to set the measurement as the voltage or
current mode, measures the voltage or current signal output by an output channel and returns a measured value to a computer; the channel and voltage / current
mode switching control plate switches a
test channel and a voltage / current connection mode according to the instruction; and the
communication interface transmits the parameter, the instruction and the test result between each device and a tested model. A computer reads the conversion value of the voltage or current measured value of the input channel through the
communication interface or transmits a set numerical value to the output channel to convert the set numerical value into a voltage or a current.