Operator`s manual

Model VR240 Audio Logging Recorder
January 2000
C-1
APPENDIX C
UNINTERRUPTABLE POWER SUPPLY (UPS)
C-1. FUNCTIONAL DESCRIPTION.
The VR240 employs a UPS to prevent AC power problems from adversely affecting the
operation of the recorder. The UPS derives its power from a multicell lead-acid storage battery
in the VR240 chassis. The battery is charged whenever the VR240 is operating; the charge rate
is normally very low (trickle charge), but increases significantly if the battery has become
discharged. The battery has sufficient capacity to run the VR240 for about two minutes if AC
power is interrupted.
The purpose of the UPS is not to allow the unit to continue operating during major power
failures. The limited battery capacity precludes this in any event, and most facilities that employ
logging recorders have a standby power source, usually a diesel-powered AC generator that
comes on automatically when primary power fails. The UPS serves two purposes:
It prevents power problems during momentary AC interruptions. AC problems can be
characterized by, among other things, their time duration. The most frequent type of problem
lasts anywhere from a fraction of an AC cycle to a few cycles. These “glitches” are typically
caused by load transients such as motors being switched on and off. Most well-designed
electronic equipment can cope with these glitches without any special precautions. The next
category is the line dropout that lasts from many cycles to a fraction of a minute. These
problems can be caused by people accidentally switching off circuit breakers, lightning strikes,
and other problems that cause a temporary interruption of service. And finally, there are serious
outages, of from many minutes to many hours or even days, caused by accidents, natural
disasters, etc. Against the first category, the VR240 needs no protection. Against the last
category, the only protection that can be provided is your own backup power source; if you do
not have one, the chances are you also have nothing to log! The middle category, multi-second
power problems, are far more frequent than natural disasters, and could be very disruptive to a
logger. Because the UPS is present, the VR240 can simply ignore brief power failures. It will
continue operating until power comes back.
Equally important, the UPS prevents media and other problems during longer outages. As
explained in Chapter 5 (paragraph 5-21), each digital media has index data recorded on it. This
is usually recorded when the media is ejected. If power were simply shut off, the index data
would be lost, and would require hours to recreate. Even worse, if the unit happened to be
recording critical information when power was lost, the media could become irretrievable. The
UPS incorporates a timer to determine whether a power failure can be ignored or requires
action on the part of the VR240.
If the failure lasts for less than about 30 seconds, it is ignored. If the failure continues beyond
30 seconds, the VR240 automatically shuts down after writing index data. It also saves
information on the cause of the shutdown and the fact that it was recording in its internal