A recording thermometer is a type of
thermometer
A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
that records
temperature
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
changes over a period of time. A
digital recording
In digital recording, an audio signal, audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure for audio, or Color, chroma and luminance values for video. This number stream is s ...
thermometer is often called a temperature data logger.
Analog temperature recorders
A type of
chart recorder
A chart recorder is an electromechanical device that records an electrical or mechanical input trend onto a piece of paper (the chart). Chart recorders may record several inputs using different color pens and may record onto strip charts or circu ...
, one end of a bi-metallic strip is attached to a long,
light metal
A light metal is any metal of relatively low density. These may be pure elements, but more commonly are metallic alloys. Lithium and then potassium are the two lightest metallic elements.
Magnesium, aluminium and titanium alloys are light metals ...
lever that holds a special pen. Tiny movements of the bimetallic strip cause much larger movements of the free end of the lever and the pen. The pen traces a rising and falling line on a strip of paper attached to a slowly turning drum. The drum usually makes one turn every seven or so days, so afterward each strip of paper contains a complete and accurate record of temperature changes for a whole week. The bimetallic strip is usually made from steel and copper. Because these metals expand and contract at different rates. When one of these metals expand it curls tighter, when one contracts it uncurls slightly. When it curls or uncurls, the data is converted into electric signals, which record the temperature change.
Digital temperature recorders
Thermocouple
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...
or
thermistor
A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on temperature. The word ''thermistor'' is a portmanteau of ''thermal'' and ''resistor''. The varying resistance with temperature allows these devices ...
s sensors coupled with
data logger
A data logger (also datalogger or data recorder) is an electronic device that records data over time or about location either with a built-in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they a ...
s are now more often used to sense and record temperatures and record them in a digital format easily used by computers. They are widely available and come in a variety of types and varying probes.
References
{{reflist
External links
Introduction to Temperature Data LoggingOmega Engineering, Inc. Retrieved 15 August 2020
Thermometers