Rapid-response monitoring circuit detects voltage decrease or dropout in any single phase or all three phases simultaneously of a 3-phase 60 Hz computer power supply. It uses lamps to indicate voltage conditions and provides a digital pulse output for a chronological record of voltage irregularities

Houck, W. H.

English

NASA Technical Reports Server

February 1968	 0 Brief 68-10019 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Circuit Detects Voltage Decrease in Computer Power Supply 
A rapid-response monitoring circuit has been de-
signed to detect a voltage decrease or dropout in any 
single phase or up to all three phases simultaneously 
of a 3-phase 60 Hz power supply for a computer. 
Rapid detector response to small voltage decreases in 
the power supply is essential to prevent erroneous 
operation of the computer. 
The circuit senses a decrease in the supply voltage 
and responds to this decrease in approximately 1.5 
milliseconds. It can be adjusted to detect a I to 10 
percent decrease of the instantaneous normal voltage 
in each cycle of the power supply. The circuit in-
corporates indicator lamps to indicate normal or 
below-normal voltage conditions and provides a 
digital pulse output for a chronological record on 
tape of voltage irregularities. The circuit may also 
be used to interrupt power to the computer (or other 
power-using equipment) in the event of a low voltage 
condition.
Notes: 
1. This circuit would, in principle, be generally 
applicable to any situation requiring close moni-
toring of an ac supply voltage. 
2. The circuit can be used to monitor two or more 
parallel ac power generators to prevent over-
loading of any one generator when a below normal 
output occurs. 
3. Inquiries concerning details of the circuit may be 
directed to: 
Technology Utilization Officer 
Kennedy Space Center 
Kennedy Space Center, Florida 32899 
Reference: B68-10019 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: W. H. Houck 
(KSC-67- 120) 
Category 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Circuit detects voltage decrease in computer power supply

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