User guide

Mirror Cleaning 37
Maintenance
Mirror Cleaning
The heart of the 973 dew point measuring instrument is the measuring head assembly. It is
designed to be highly sensitive and accurate, yet rugged and easily accessible for periodic
mirror cleaning.
Removing the Head Cover Screw or Retaining Bar
The measuring head is located on the right side of the
973 front panel. To gain access to the mirror and opto-
electronic components, you must first remove the cover
screw by twisting it counterclockwise. It requires
approximately three full turns to completely unscrew,
allowing you to remove it.
Once the cover screw has been removed, the black
optical assembly (optical head) is now removed by
pulling it straight toward you. This piece contains the
light emitting and light sensing opto-electronic elements.
There is an oval shaped o-ring on the face of the optical
assembly that is used to seal it to the measuring head.
There are also some gold contacts on the face. Avoid
touching the face of the optical assembly with your
fingers to prevent contamination of the contacts, the o-
ring, the optical area, and the gas channel.
Inspecting / Cleaning the Mirror
The mirror requires occasional periodic cleaning to maintain high accuracy measurements.
The flush mounted mirror is easily accessible by removing the cover screw and optical mirror
assembly. Look at the mirror with the naked eye or with a magnifying glass. If signs of
contamination are present, or suspected of being present, use the following procedure to
clean the mirror.
1. Clean the mirror with a clean, wet cotton swab or
lint free tissue.
2. Follow with a damp cotton swab or tissue.