Gas detection

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World Leader In Gas Detection & Sensor Technology

Gas Detection History

Gas Detection History
First Gas Monitors
Canary in a cage
 Canaries are more
susceptible than humans to
low oxygen, methane gas,
or CO gas.
 A passed out canary
means a dangerous gas
 Generally two canaries

Gas Detection History
Flame Safety Lamp (Davey’s Lamp)
 Invented by SirHumphry
Davey (of England) in 1815
 Oil flame adjusted to specific
height in fresh air
 Flame contained within a glass
sleeve and with a flame
 High flame means methane
gas present
 Low flame means low oxygen

Gas Detection History
Catalytic Combustion (LEL) Sensor
 Developed by Dr. Oliver
Johnson 1926-1927
 Working for Standard Oil
Co. of CA (now Chevron)
 Need was toprevent
explosions in storage tanks
on oil and gasoline tankers

Dr. Oliver Johnson

Gas Detection History
Catalytic Combustion (LEL) Sensor
 Principle : Hot wire catalytic platinum
filament oxidizes flammable gases or
vapors at lower levels than they
would normally oxidize in air.
 Oxidizing gases or vapors cause
increase in temperature of hot wires
which increases electricalresistance
of the wire.
 Second not wire not in gas stream
used as a reference filament.
 Resistance change measured with
W heatstone bridge to deflect a meter.

Gas Detection History
Catalytic Combustion (LEL) Sensor
 First instrument Model A
demonstrated in 1926 using
2 jar method shown.
 Only one Model A built, for
demonstration purposes.

Gas Detection History
Model B LELMonitor
 1927 Introduction
 First practical production
model of LEL meter (weighs 12 lb)
 Approx. 100 units made
 PG&E used for 50 years
 2 meters: 1 for gas reading
& 1 for sensor voltage
(critical adjustment)
 20 made by Dr. Johnson while at
Standard Oil
 Called the “Standard Oil Electric Vapor Indicator”
 Used hand aspirator to draw sample

Gas Detection History
Sensor forModel B
 2 filaments in a glass tube
 One tube sealed as the
reference element
 Instrument remained outside
the hazardous area
 Flame arrestor on sample
inlet prevented flashback into
tested space

Gas Detection History
Johnson-Williams Instruments
 Formed in 1928, Palo Alto, CA
 Started by Dr. Oliver Johnson &
Phil Williams
 Recognized as the first
“Electronics” company in“Silicon Valley”
 Trademarked “J-W Sniffer”
 Manufactured 80 more of the
Model B J-W indicator
Dr. Oliver Johnson

Gas Detection History
J-W “Sniffer” Model C

Smaller & lighter than Model B
Approx. 300 units built
Accepted by US Navy
Had flame arrestor approval
for acetylene use

Gas Detection History
 1929/1930 Borrowed J-W Model C for 3 months
Initially indicated to J-W they may want to sell
Model C
 Returned meter with letter; “Does not fit into
MSA marketing plans”
 6 Months later MSA introduced their own LEL
meter with same characteristics as Model C
 World’s second gas detection company

Gas Detection History
MSA Explosimeter Model 2A
 1935 Introduction
 MSA’s 2nd design
 Popular rugged unit, still in
use today
Uses 8 D-cell batteries
 Used unbalanced bridge
circuit (no reference

Gas Detection History
 1925-1927
 Dr. Uzumi Doi did initial
research in 1927 at the Institute
of Physical & Chemical
Research in Japan
 Dr. Ziro Tsuji of the Institute
developed the first working
 Developed to help prevent
explosions on oil tankers, and
in coal minesDr. Tsuji

Gas Detection History
 Uses principle of light
diffraction in air to
indicate presence of
methane or gasoline
 Light diffraction creates
visible fringe lines that
shift to indicate gas

Gas Detection History
Interferometer (Riken Keiki)
 1935: 40 units sold to coal
mine in Hokkaido
 1938: Dr Tsuji re-invented,
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