Temperature Measurement Tips
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 where measurements are taken 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. If you need to convert heat into CO2 generated or degrees Fahrenheit to degrees Celsius check out the conversion page.
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 to cover the surface to be measured 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.