Nanometrics RM-4, User Manual

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Keeping water out
The RM-4 is not waterproof. When operating outdoors, it must be contained within a waterproof
enclosure.
Fuses
The RM-4 is protected with a surface-mount fast-acting 0.75A fuse. For units with standard 5V
power, this fuse is installed at F1, for 12 V power, the fuse is installed at F2.
GPS Backup Power Battery
An RM-4 with GPS has a 7 mA
$
h, 3.3 V Lithium battery to provide backup to the RAM and real-time
clock. The RAM stores the GPS almanac, ephemeris, and last position, to aid the engine in locating
satellites when power is restored. Typical consumption is 2
l
A, so the GPS should be able to retain
this information for about 20 weeks without external power.
When is it safe to turn power off?
Power can be removed from an RM-4 temporarily without loss of data. (The amount of time
depends on the size of the smallest buffer on the HRD.) The central NAQS acquisition computer in
the network will rerequest missing data as soon as power to the RM-4 is restored.
Packaging
Enclosure
The RM-4 is packaged in a steel and aluminum box measuring 7.25" wide by 9.5" long by 1.5" high.
The top cover and front and rear panels are computer beige; the bottom is bare aluminum. The front
and rear panels are made of anodized aluminum, with Lexan graphic overlays. The panels are
fastened to the bottom tray with #4-40 self-tapping screws. The enclosure is not waterproof.
All electronic components are installed on one PCB which slides into the aluminum extrusion tray
of the box. Chassis ground on the PCB makes contact with the bottom plate of the box through the
rails on which the PCB sits. In addition, the rear panel is grounded through the connector shields,
and the front panel through conductive gasketing. Chassis ground is earthed through the power
connector.
RM-4 Manual 8
4 - User Guide