Use of a differential voltage comparator as an alarm level control

Conference · Sat Jan 01 04:00:00 EST 1972

OSTI ID:4298463

Chester, J; Willis, C A ^[1]

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1. ed.

The purpose of most fixed radiation monitoring instruments is to provide in alarm when the radiation levels being monitored exeed a predetermined value. It is therefore necessary to provide reliable alarm circuitry if the primary instrument is to be effective. Although meter relays are the most common alarm level controls now in use they have several limitations. Contact type relays prevent the indicating meter from exceeding the alarm set point and they are limited to only one up-scale point and one down-scale point. The non-contact type meter relay is expensive and in both types the alarm level can only be set at the indicating instrument. The disadvantages of the meter relay can be overcome by using a differential comparator in the form of an integrated circuit which is small, reliable and inexpensive. It can be connected to operate with either a positive or negative signal. The alarm level control can be set accurately and is stable over long periods of time. The control can be located on the primary indicating instrument or at any remote location. The circuit requires so little power from the indicating instrument thnt several alarm points can be used. The circuit is wired in a fail-safe manner in that any failure of the indicating instrument, the differential comparator, or any other component will result in an instrument failure alarm. Alarm circuits using Fairchild VA 710 differential comparators have been in use at Brookhaven's High Flux Beam Reactor air monitoring system for over a year without failure. (auth)

• Research Organization: Brookhaven National Lab., Upton, NY
• NSA Number: NSA-29-029487
• OSTI ID: 4298463
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*ALARM SYSTEMS-- COMPARATOR CIRCUITS
*RADIATION MONITORS-- ALARM SYSTEMS
N46110* --Instrumentation--Radiation Detection Instruments-- General Detectors & Monitors
OPERATION
PERFORMANCE COMPARATOR CIRCUITS