Temperature

Overview:

Temperature is a physical property of a system that uses the concepts of hot and cold. The object becomes hotter as the temperature increases and vice versa. Macroscopically, temperature determines the direction of heat flow between two objects placed in thermal contact. If the two objects have the same temperature, no heat flow occurs, otherwise heat flows from the hotter object to the colder object.





Microscopically, temperature can be defined as the average energy of microscopic motions of a single particle in the system per degree of freedom. In a solid or liquid, these microscopic motions are principally the vibrations of its atoms about their sites in the solid or liquid. In an ideal monatomic gas, the microscopic motions are the translational motions of the constituent gas particles, while a multiatomic gas also include vibrational and rotational motions.
 

Method:

Temperature Scales

Temperature is measured with thermometers that may be calibrated to a variety of temperature scales that include:

• The Celsius scale, °C
• The Kelvin scale, K (0 K= -273.15 °C)
• Fahrenheit scale
• Rankine scale (a shifted Fahrenheit scale)

Temperature Probes

Thermocouples
Thermocouples are commonly used for temperature measurement as they are highly accurate and operate over a broad range of temperatures. They consist of two different metal wires that are welded together at one end (A). These wires generate a thermoelectric voltage between their open ends that changes according to the temperature difference between the two ends, that is, between junction (A) and the reference (R).

Thermistors
Thermistors consist of an electronic component (semiconductor material) that exhibits a large change in resistance in proportion to a small change in temperature. In comparison to thermocouples, thermistors have a limited (smaller) temperature range; however, they are highly sensitive within this range. The resistance of these devices often changes in a non-linear fashion with temperature and additional instruments required to linearize the reading.

Note: Temperature probes may be used to determine cardiac output using the thermodilution method. See the Cardiac Output application page for more information

 

Software:

LabChart
LabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.

GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.

 

Hardware:

Each temperature probe requires its own type of preamplifier which provides a signal to a PowerLab data acquisition system.

Thermistors & Preamplifiers

These temperature probes connect to PowerLab data acquisition systems via a

• ML221 Bridge Amp
• ML117 GP Amp
• ML309 Thermistor Pod

They include:

• MLT415/M Thermistor Temperature Sensor
• MLT415/A Nasal Temperature Probe
• MLT415/D Nasal Temperature Probe
• MLT422/D Skin Temperature Probe (DIN; 2 m)
• MLT422/A Skin Temperature Probe (2 m)

They are used to measure skin surface temperatures or nasal air temperatures (a useful indicator of respiratory rate) in the range 5°C to 45°C.

Thermocouples & Preamplifiers
The T-type thermocouple probes have a 2-pin T-type plug that is suitable for connection to data acquisition systems via a:

• ML312 T-type Pod
• ML313C Cardiac Output Pod (with Ultra-fast T-Type Thermocouple (IT-23))
• ML313 Cardiac Output Pod (no thermocouple)
• ML290-V Thermometer for T-type Thermocouples

The Ultra-fast T-Type Thermocouple (IT-23) is recommended for use with the ML313 Cardiac Output Pod.

The thermocouple probes include:

• MLT1404 Rectal Probe for Mice (RET-3) – a probe suitable for measuring the body temperature in small animals such as mice, hamsters or rat pups. The probe consists of a thin stainless steel shaft 19 mm long, with a smooth ball tip of 1.7 mm diameter.
• MLT1403 Rectal Probe for Rats (RET-2) – a probe suitable for measuring the body temperature in adult rats. The probe consists of a stainless steel shaft 25.4 mm long, with a smooth ball tip of 3.2 mm diameter.
• MLT1407 Large Animal Rectal Probe (RET-1) – a probe suitable for measuring body temperature in rabbits and larger animals. The probe consists of a flexible, vinyl covered, soft tip with a 1.5m lead and can measure a maximum temperature is 90°C with a time constant of 5.0 seconds.
• MLT1406 Needle Microprobe Thermocouple (MT-29/1) - a fast-response needle thermocouple probe which can be used for measuring temperature in tissues, semi-solids and liquids.
• MLT1400 General Purpose Thermocouple Probe (HT-1) - a probe suitable for measuring temperature in liquids, gases and semi-solids. It has a plastic handle and a 75 mm long stainless steel shaft, and is suitable for temperature measurements to a maximum of 400 °C.
• MLT1401 T-type Implantable Thermocouple Probe (IT-18) - a 0.6 mm diameter implantable probe is suitable for immersion in various solutions, semi-solids and tissue. It can also be used to measure rectal temperatures of small animals and is suitable for measuring temperatures up to 150 °C.
• MLT1402 T-type Ultra Fast Thermocouple Probe (IT-23) - a tissue implantable microprobe with an ultra fast response time of 0.005 seconds. The tip of the thermocouple is just 0.76 mm in diameter, and is inserted into tissue with a supplied 23 gauge hyperdermic needle. It is suitable for temperature measurements to a maximum of 150 °C.
• MLT1405 T-type Implantable Thermocouple Probe (IT-21) - a 0.4 mm diameter implantable probe is suitable for immersion in various solutions, semi-solids and tissue. The isolated probe is totally sheathed in chemical resistant Teflon and is rugged. It can measure temperatures up to 150 °C.

Additional Hardware & Accessories

• ML165 pH Amp - a dual function amplifier capable of measuring pH and temperature. The unit is supplied with an RTD Temperature Probe.
• MLT1101 Thermocouple/Analog Converter - converts a thermocouple input signal to a cold junction compensated, linear, amplified analog output. The connector is supplied with a MLAC09 BNC-Banana Plug Adapter for connection to a PowerLab BNC input
• ML880B103 Telemetry Biopotential Foundation System - contains hardware and software that is capable of measuring body temperature simultaneously
• ML880B107 Telemetry SNA and Pressure Foundation System - contains hardware and software capable of measuring body temperature simultaneously

Comparison of intracranial pressure measured in the cerebral cortex and the cerebellum of the rat
S Rooker, G de Visscher, B van Deuren, M Borgers, P G Jorens, R S Reneman, K van Rossem and J Verlooy, Journal of Neuroscience Methods, 83-88, 2002

5'-Adenosine monophosphate and adenosine metabolism, and adenosine responses in mouse, rat and guinea pig heart
J P Headrick, J Peart, B Hack, B Garnham and G P Matherne, Comparative Biochemistry and Physiology A, 615-631, 2001