Special joint for overall alignment calibration of CalScan small-diameter pressure gauge

The invention provides a special joint for overall alignment calibration of a CalScan small-diameter pressure gauge. The special joint comprises an alignment calibration barrel, wherein the alignment calibration barrel is a hollow cylinder; the upper part of the alignment calibration barrel is hermetically connected with a seal pressing cap which forms a sealed space together with the hollow alignment calibration barrel; the seal pressing cap is provided with internal threads; the internal threads are internally provided with an insert hole; the lower part of the alignment calibration barrel is hermetically connected with a lower joint; the insert hole is reserved in the internal threads of the seal pressing cap and a data line can be inserted into the insert hole, so that real-time data acquisition is realized. The special joint can be connected with a DH50000-II full-automatic alignment calibration system pressure transmission pipeline; by virtue of matched use of the alignment calibration barrel, the seal pressing cap and a small-diameter pressure gauge, a sealed pressure-bearing environment is supplied to the small-diameter pressure gauge; the insert hole is reserved in the internal threads of the seal pressing cap and the data line can be inserted into the insert hole, so that real-time data acquisition is realized; by virtue of simple maintenance, the special joint can be repeatedly used.