A field testable instrument housing connection for field testing of multiple parallel seal connections between outer and inner concentric tubes, the inner tubes carrying electrical and/or optical conductors to be connected to sealed instruments, the field testable instrument housing connection comprising: a. a hermetically sealed metal instrument housing; and characterized by b. a reducing union having a uphole portion and a downhole portion; with an uphole end metal tube seal and a downhole end metal tube seal, providing both an annular seal and a seal of the metal instrument housing, with the uphole end metal tube seal having means for testing seal integrity; c. a concentric inner tube passing from uphole to downhole completely through said reducing union; d. an integral instrument housing assembly, wherein the uphole portion of the reducing union lies outside of the integral instrument housing assembly, the integral instrument housing assembly comprising: i. the metal instrument housing having an uphole and a downhole portion, with said uphole portion having a mating seal geometry on its uphole end so that said uphole end is disposed over the downhole end of said reducing union; ii. a compression nut portion through which said reducing union is inserted, the compression nut portion having means for testing seal integrity including a test port and test port plug; e. an outer concentric tube passing from uphole to downhole and terminating inside the uphole portion of the reducing union that lies outside of the integral housing mating assembly; f. a metal seal against the reducing union body and located within said compression nut portion; g. wherein said mating seal geometry of said integral metal instrument housing mates with said metal seal against the reducing union body and said compression nut portion to form a metal hydraulic seal against the reducing union body; h. an uphole test seal element and a downhole test seal element positioned on either side of said metal seal against the reducing union body; i. a test port positioned between said uphole test seal element and said metal seal against the reducing union body. a. a hermetically sealed metal instrument housing; and characterized by b. a reducing union having a uphole portion and a downhole portion; with an uphole end metal tube seal and a downhole end metal tube seal, providing both an annular seal and a seal of the metal instrument housing, with the uphole end metal tube seal having means for testing seal integrity; c. a concentric inner tube passing from uphole to downhole completely through said reducing union; d. an integral instrument housing assembly, wherein the uphole portion of the reducing union lies outside of the integral instrument housing assembly, the integral instrument housing assembly comprising: i. the metal instrument housing having an uphole and a downhole portion, with said uphole portion having a mating seal geometry on its uphole end so that said uphole end is disposed over the downhole end of said reducing union; ii. a compression nut portion through which said reducing union is inserted, the compression nut portion having means for testing seal integrity including a test port and test port plug; i. the metal instrument housing having an uphole and a downhole portion, with said uphole portion having a mating seal geometry on its uphole end so that said uphole end is disposed over the downhole end of said reducing union; ii. a compression nut portion through which said reducing union is inserted, the compression nut portion having means for testing seal integrity including a test port and test port plug; e. an outer concentric tube passing from uphole to downhole and terminating inside the uphole portion of the reducing union that lies outside of the integral housing mating assembly; f. a metal seal against the reducing union body and located within said compression nut portion; g. wherein said mating seal geometry of said integral metal instrument housing mates with said metal seal against the reducing union body and said compression nut portion to form a metal hydraulic seal against the reducing union body; h. an uphole test seal element and a downhole test seal element positioned on either side of said metal seal against the reducing union body; i. a test port positioned between said uphole test seal element and said metal seal against the reducing union body.