Method for testing transmission distortion of 4-20mA signal transmitted by field measurement and control

The invention discloses a method for testing transmission distortion of 4-20mA signals transmitted by field measurement and control, and the structure of a test circuit is as follows: an ampere meter 1 and an ampere meter 2 are respectively connected in series at a power distribution module of a central control power distribution room of a test line and at the field of a production system measurement transmitter, and an R line represents the insulation resistance of a cable transmission line; the field transmitter is represented by a variable resistor RL; when the ampere meter 1 and the ampere meter 2 display that the current is consistent, the insulation resistance of the transmission line has no problem, that is, the R line is infinite; when the ampere meter 1 and the ampere meter 2 display that the current is inconsistent, the insulation resistance of the transmission line goes wrong, that is, shunt current flows through the R line. A precise process point detection test is carried out on measurement and c