Temperature
Measurement Tips
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Measuring The Temperature Of Solid Objects
For example measuring the temperature of central heating pipes
when balancing the central heating system or measuring the temperature
drop between each end of a pipe to check the efficiency of pipe
insulation. When making any measurement it is important that objects
are at a stable temperature. It is also important that pipes
are not painted since the paint acts as an insulator. The information below is specifically aimed at metal pipes and fittings. When dealing with plastic pipes the only real option is to use any metal joints and fittings where available to measure temperature.
Digital Thermometers
You get more consistent results if a small amount of heat conducting
grease is used on the end of the sensor but you do have to clean
up afterwards.They are best used on the Fahrenheit scale since
you get nearly twice the sensitivity. It is best to use a thermometer
with a small probe area, avoid ones that are designed to be inserted
into liquids. It is important to ensure the measured temperature
has stopped changing. Erratic readings usually indicate a measurement
problem.
Infra Red Thermometers
Non
contact infra red thermometers are much easier and quicker to use
but apart from costing more have the drawback that they can give
inaccurate readings on shiny surfaces. I got around this originally
by placing a small piece of black tape at each point on the pipes
I want to measure, however the tape acts as an insulator and although
readings were consistent they were a bit lower than the actual
temperature. My final solution which won't suit everyone is to
use a black marker pen which gives a very thin layer hence giving
more accurate results. Experience of this type of device was obtained
with a Precision Gold N28BJ from Maplin
Electronics. The key point is to make sure the distance from
the object being measured is consistent with the Infra Red beam
angle which can be obtained from the user guide and the area of
the object being measured. I suspect the absolute accuracy is not
fantastic but as most results are relative this will not matter
too much.
Clip On Mechanical Thermometers
These are fine for
clipping on to pipes but do take a long while to stabilise so are
not very useful for moving around. Also to give accurate results
they need to be a good fit to the pipe which gets complicated when
dealing with several different pipe sizes. Use of heat conducting
grease on the mating surfaces improves the accuracy.
Mercury or Alcohol Thermometers
These are only really suitable for measuring liquid or air temperature. When measuring air temperature make sure the thermometer is shielded from draughts, is not in direct sunlight and is given plenty of time to stabilise.
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