Biological Temperature

Overview:

Temperature is one of the most common types of physical measurements. It is the measure of the average kinetic energy of particles in a substance (solid, liquid, gas). Temperature is the result of the motion of particles. Temperature increases as the energy of this motion increases. The motion may be the translational motion of the particle, or the internal energy of the particle due to molecular vibration or the excitation of the electron energy level. Temperature is measured in degrees on the Fahrenheit, Celsius, and Kelvin scales.

Method:

The simplest method of measuring temperature is to use a thermometer. A thermometer is typically a glass cylinder with a bulb at one end and a capillary hole down the axis connected to the reservoir in the bulb filled with silvery liquid mercury or a red-colored fluid. The engraved temperature scale is calibrated to a variety of scales including;

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

Depending on the desired accuracy, range, and budget, there are several sensor options for measuring temperature. ADInstruments offer a range of Thermocouples, Resistive Temperature Devices (RTDs) and Thermistors which can generate data that is easily recorded or transmitted. If an analog output is available then PowerLab can be used to measure temperature change in real-time.

Thermocouples
Thermocouples are commonly used for temperature measurement as they are highly accurate and operate over a broad range of temperatures. They consist essentially of two different metal wires that are joined 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). For small changes in temperature, the voltage is approximately linear however, as temperature goes up, the output of the thermocouple rises, though not necessarily linearly.
 

Resistance Temperature Devices (RTDs)
A Resistance Temperature Device (RTD) is a device made of coils or films of metal (usually platinum). RTDs rely on resistance change in a metal, with the resistance rising relatively linearly with temperature. When heated, the resistance of the metal increases; when cooled, the resistance decreases. Passing current through an RTD generates a voltage across the RTD. By measuring this voltage, you can determine its resistance and, thus, its temperature.

Thermistors
Thermistors are based on resistance change in a ceramic semiconductor; that exhibits a large change in resistance in proportion to a small change in temperature. Passing current through a thermistor generates a voltage across the thermistor and determine its 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 drops nonlinearly with temperature rise.

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

Software:

The LabChart Advantage:

(may require additional Modules and Extensions)

• Units Conversion for easy calibration into appropriate units such as °C, K, F, etc
• The Multipoint Calibration Extension performs linear and non-linear calibration on thermocouples, RTDs, thermistors and other equipment
• Comments can be added in real time, viewed or moved at a later stage
• Fast data extraction, analysis and export (e.g. csv. or txt.) to other applications using Timed Add to Data Pad and Multiple Add to Data Pad
• The Event Manager Extension can be used to monitor an incoming temperature signal and perform a user defined action such as adding a comment, playing a sound, flashing a light, etc when the temperature signal rises above/below a set threshold level.

LabChart

LabChart software (for Windows and Macintosh) together with a PowerLab data acquisition system offers up to 32 channels of real-time data acquisition, data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Additional acquisition and analysis functionality is provided with the use of specialized LabChart Extensions and LabChart Modules. Modules are available as part of LabChart Pro while Extensions are free for download from the website for existing LabChart users.  

Multipoint Calibration

The Multipoint Calibration Extension (Win and Mac) extends Units Conversion in LabChart to allow you to perform linear and non-linear corrections on any input using up to 12 standard points. The Extension may be used online, while data is recording, or offline with previously recorded data. The calibration points should span the highest and lowest signals that you expect to encounter in your experiment. Various fitting functions are provided by the Multipoint Calibration Extension. The functions (except Point to Point) are fitted by least squares to your calibration points.

Note: Some calibration functions (especially polynomials) can work poorly if subsequently used with data outside the calibration region.

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:

PowerLab Data Acquisition Systems

The PowerLab is a high-performance data acquisition unit capable of recording at speeds of up to 400,000 samples per second continuously to disk (aggregate). PowerLab units are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other third-party companies. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. Research PowerLab units include:

• PL3504 PowerLab 4/35 - 4 Channels
• PL3508 PowerLab 8/35 – 8 Channels
• PL3516 PowerLab 16/35 – 16 Channels

Instruments

• ML290-V Thermometer for T-type Thermocouples: A battery operated thermometer for use with T-type thermocouple probes. Supplied with a stand and an analog cable for connection to a PowerLab.
• ML295/R Homeothermic Controller and Plate (for rats): Used for maintaining temperature in rats during acute or chronic anesthesia.
• ML295/M Homeothermic Controller and Plate (for mice): Used for maintaining temperature in mice during acute or chronic anesthesia.

Signal Conditioners

• FE221 Bridge Amp
• ML142 GP Amp
• ML309 Thermistor Pod
• ML312 T-Type Pod
• ML313C Cardiac Output Pod (with Ultra-fast T-Type Thermocouple (IT-23)
• ML313 Cardiac Output Pod (no thermocouple)
• ML165 pH Amp: A dual function amplifier capable of measuring pH and temperature. The unit is supplied with an RTD Temperature Probe.

Transducers and Accessories

Thermistors

The ADInstruments range of Thermistors 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. Suitable for connection to PowerLab via the ML309 Thermistor Pod (/A) or FE221 Bridge Amp (/D).

• 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)
• MLT415/M Thermistor Temperature Sensor: A sensor used with the Gas Mixing Chamber for measuring air temperature during gas analysis.

Thermocouples

The T-type thermocouple probes have a 2-pin T-type plug that is suitable for connection to PowerLab via the ML312 T-type Pod or ML290 Thermometer for T-type Thermocouples.

• 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.
• 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.

Hypothalamic paraventricular nucleus is critical for renal vasoconstriction elicited by elevations in body temperature
Cham J L, Badoer E, American Journal of Physiology: Renal Physiology, F309–F315, 2008

Nonselective NOS inhibition blunts the sweat response to exercise in a warm environment
Welch G, Foote KM, Hansen C, Mack GW, Journal of Applied Physiology, 796-803, 2009

Augmented photoplethysmographic low frequency waves at the onset of endotoxic shock in rabbits
Gregory S H Chan, Collin H H Tang, Paul M Middleton, Grant Cave, Martyn Harvey, Andrey V Savkin and Nigel H Lovell, Physiological Measurement, 1605–1621, 2010