Stem diameter variation monitoring transmitter for crop moisture state

The invention belongs to the technical field of agricultural water-saving irrigation and particularly relates to a stem diameter variation monitoring transmitter for the crop moisture state. The stem diameter variation monitoring transmitter comprises two parts, namely a probe and a processing circuit, wherein the probe comprises a displacement sensor, a probe bracket and a constant force spring bracket, a concave stretching movable support frame for fixing rolling constant force springs is fixed on a measuring push-pull rod of the displacement sensor, two same rolling constant force springs are symmetrically mounted at the right upper part and right lower part of the constant force spring bracket, and stretching ends of the two same rolling constant force springs are respectively symmetrically fixed on the upper side and lower side of the concave stretching support frame. According to the stem diameter variation monitoring transmitter, as being throughout maintained at optimal sizes due to the size of a force applied to a stalk by the measuring push-pull rod, the rolling constant force springs do not need to be adjusted until the whole measuring range of the measuring push-pull rod is compressed, and the influence of the growth of a plant stem to a stem diameter variation monitoring result is overcome; the processing circuit utilizes a nonconventional manner that the power is independently supplied to the displacement sensor by utilizing external high-precision voltage reference, so that the stability is good; the structure is simple, and the cost is low.