T E C H N O L O G Y
TC-1
I’ve always been able to get along by
eyeballing the flame. Why should I use a
mechanical or electronic instrument?
As amazing as the human eye is, it is not capable of per-
forming quantitative analysis of changing colors in
widely varying surroundings and situations.
The only quantifiable analysis that you can depend on
is achieved through the use of mechanical or electronic
instrumentation.
TC-2
If mechanical instruments will do the job why
should I use electronic instruments?
As mentioned in the combustion analysis section, elec-
tronic instrumentation has several other benefits which
are important.
The speed and accuracy of electronic instrumentation,
coupled with the convenience of a computer, allows
you to create hard copy reports which eliminates
tedious, time consuming and frequently inaccurate,
handwritten reports.
In our society, the increasing demand for pollution con-
trol and the increased possibility of severe fines or legal
actions has made all of us more aware of the need to be
able to demonstrate, in a tangible way, that we have
performed as professionals and have done everything
possible to insure environmental and safety compliance.
E l e c t ronic instrumentation combines higher levels of
accuracy with faster testing, and demonstrable hard copy
evidence of date, time and results of testing. This will
p rovide you the most accurate and most cost eff e c t i v e
way to assure that the information you need to perf o rm
as a professional is always available and easy to re t r i e v e .
In addition to continuous testing, many electronic
instruments will allow you to transfer and store infor-
mation in a computer. This information can be identi-
fied and logged to allow you to generate a “history” of
each individual piece of combustion equipment that
you test.
By referring to this “history,” you will have a solid ref-
erence point for the levels of fuel efficiency, safety, and
environmental compliance achievable for any boiler or
furnace that you test.
TC-3
What is the biggest diff
e rence between
mechanical and electronic instruments?
The most important difference is the elimination of
potential human error.
Electronic instruments simplify testing, eliminate the
need for interpretation of measurements, and perform
error free combustion calculations automatically.
TC-4
What are the advantages of using electronic
instruments for combustion testing?
In addition to the advantages which we have detailed
before, many service personnel have told us that the
advantages of using electronic instruments are: speed
and ease of use, automatic sampling, automatic calcu-
lations and automatic report generation.
Electronic instruments also provide individual displays of
O
2
, CO, NO
X
, etc., which allow immediate monitoring
and independent analysis of each adjustment as it is
made on a boiler or furnace.
TC-5
What type of sensors are used in electronic
instruments?
Although sensors are manufactured for specific gases
and have small but significant differences, the basic
concept for sensors used to measure carbon monoxide
(CO), nitric oxide (NO) and sulphur dioxide (SO
2
) are
very similar.
Electrochemical sensors are entirely contained within a
sealed plastic capsule or body. The major working ele-
ments are three coated electrodes (sensing, counter and
reference) and a small volume of an acid solution.
In use, the gases diffuse through a small orifice on the
sensing face of the sensor to the electrode surface and
cause a change in the measured gas, which initiates a
small electrical current.
The current, which is directly proportional to the con-
centration of gas being measured, is amplified and
scaled by the electronics. The value is then displayed or
is available for printing or downloading to the comput-
e r, depending on the instrument being used.
Electrochemical oxygen sensors are manufactured and
operate in a slightly different way.
Oxygen sensors are also entirely contained within a
sealed plastic body which contains a consumable
counter electrode (usually lead), a sensing electrode and
a small volume of a base solution.
In use, oxygen diffuses through a membrane which
covers the face of the sensor, the gas contacts the sens-
ing electrode and the base solution and reacts at the
wet surface of the electrode. This reaction consumes
the counter electrode.
The chemical change in the counter electrode allows a
circuit in the instrument to measure a potential (volt-
age) between the sensing and counter electrodes. This
voltage is directly proportional to the concentration of
oxygen in the gas being sampled. The value is then dis-
played or is available for printing or downloading,
depending on the analyzer being used.
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