In-situ near infrared sensor unit and method of making the same

A near infrared sensing unit comprising:

• a tubular housing including a sidewall extending between a first end and a second end;
• a transparent window formed in the sidewall of the housing;
• a sensing element mounted inside the housing, the sensing element configured to emit near infrared light and configured to collect near infrared light;
• a mirror mounted inside the housing and opposite the sensing element, the mirror mounted at an angle with respect to the transparent window, the angle allowing the mirror to reflect the near infrared light, emitted by the sensing element, through the transparent window;
• a conical tip connected to the first end of the housing, the conical tip configured to penetrate a media;
• and
• a carriage disposed in the tubular housing, the carriage having an exterior surface abutting the sidewall;
• wherein the carriage includes a mirror recess formed in the exterior surface, the mirror recess defined by a first surface and a second surface, the second surface including a mount recess configured to hold the mirror at the angle with respect to the transparent window;
• and
• a sensor mount formed in the carriage, the sensor mount configured to hold the sensing element opposite the mirror;
• wherein the carriage is positioned inside the housing such that the mirror and sensing element are adjacent the transparent window.