Physitemp's miniature Type T thermocouple sensors provide the wide stand most versatile selection of temperature probes available for bioscience and analytical chemistry applications. All clinical probes and microprobes are made with Physitemp's proprietary copper-constantan thermocouple wire and are guaranteed accurate to 0.1°C within the physiological range. All probes are interchangeable and do not require individual calibration when used with any of our Type T thermocouple instruments.  

Physitemp's tiny sensors, welded under microscopes, are used to make needle probes as small as 29 gauge and flexible probes with a diameter of .005". Small mass results in fast response times, with time constants as low as .005 seconds.  

Physitemp's best selling probes, the flexible 1T- 18  series, are used in many scientific and industrial applications; for implantation in tissue, in spectrophotometer cuvettes, rectally in neonatal mice, and in water baths. They are fast reading, strong, completely sealed in flexible Teflon® and may be sterilized by gas (ETO) or autoclave.  

Stainless steel needle probes as small as  .033mm diameter are available. There are surface probes, animal rectal probes in several sizes, heavy duty probes and a wide range of clinical probes. Physitemp also make custom probes in any quantity including multisensor microprobes with as many as 10 sensors.  

High accuracy is guaranteed 
Physitemp specializes in the manufacture of Type T (copper-constantan) thermocouples. Small, flexible sensors are in demand for use in medical applications where high accuracy and interchangeability are required. Type T wire is widely recognized as being the most suitable thermocouple for these applications.

Accuracy of ±0.l°C in the physiological range is possible and the probes are completely interchangeable. Wire with only ±0.5°C accuracy is readily available. This is known as "Special Limits" wire. Physitemp is a supplier of the premium grade with accuracy to 0.l°C.  

Advantages of Thermocouples  
There are currently six different common techniques for measuring temperature : thermal expansion, such as the bimetallic  strip or liquid-in-glass thermometers, bulk resistance devices such as platinum RTD's and thermistors, semiconductor devices including diodes and transistors, thermocouples, liquid crystals and infrared noncontact devices. Of all the contact measure­ments techniques listed above the thermocouple is the smallest in size, fastest responding and lowest cost. This offers the least perturbation to the object being measured, and hence, the most accurate interpretation of its temperature. Their wide operating range and low relative cost make thermocouples ideal for most bioscience and industrial applications.  

What are thermocouples ?  
A thermocouple is a junction of two dissimilar metals and exhibits galvanic activity in response to a temperature gradient across the junction. Many conductors exhibit this effect, however in practice only eight or nine different types of thermocouples are used extensively in a vast array of industrial, commercial, medical and research applications. Selection of a thermocouple e for a specific application is related to cost, temperature range, accuracy, stability and operational life expectancy.  

A thermocouple sensor is created wherever the wires comprised of the two dissimilar metals are joined together electrically.  

The junction is usually a welded connection because this minimizes the size of the junction and provides the fastest response time. In addition, because the weld melts at such a high temperature it enable s the probe to be used over a much wider temperature range. The sensor may also be formed by soldering or crimping, neither of which will affect the accuracy of the junction in measuring temperature although the response time may be slower and the melting point and corrosion resistance of the sensor junction may suffer when soldered. Since most of Physitemp's thermocouples are made under a microscope, the quality and consistency of each weld is very high.  

Isolated vs. Non-isolated
In a non-isolated sensor, the thermocouple bead is in direct contact with the object being measured, or it is in electrical contact with an outer and electrically conductive sheath that is in contact with the object. The advantage of the non-isolated sensor is the improved response time in both the sheathed and unsheathed forms.  

An isolated sensor may be needed in an electrical application or one in which more than one sensor is present in a conductive medium. If the object being measured is electrically conductive and at an elevated potential, it is especially important in order to prevent an electric shock to the operator or damage to the measuring instrument.  

In many medical applications invasive sensors may be in contact with internal body fluids which are comprised of conductive electrolytes. Isolated sensors are required in these applications to avoid galvanic interaction between temperature sensors and other types of electrical sensors such as EKG electrodes.  
                                              

HT-1  “Workhorse” Probe for liquids, gases semi-solids. Plastic handle with straight 3” stainless shaft. Not good for surface temps.  Max. Tem. 400°C. Time constant 0.5 secs. 5ft.lead.  Not isolated.
HT-2   As HT-l but with 9" shaft.  

BT-1   For surface temperatures of solids, also for liquids, gases  and semi-solids. Probably our best general purpose probe.
Welded stainless-steel shaft, plastic handle. Tip is 0.028" diameter  bent at right angle to probe to facilitate accurate surface measurements. 5 ft. lead. Immersible. Max tip temp. 240°C. Time constant  

DPT Series   Immersion probes for liquid. #304 stainless steel  welded shaft, wooden handle. 5 ft. lead. Max. Temp. 400°C . Time constant 2 secs. Not isolated. TFT Series - Immersion probes for corrosive liquids. Similar to  DPT series but shaft is Teflon-coated Max. Temp. 150°C  

PT-6  Sensor Six-Pack. For multi-point measurements.
Inexpensive, flexible. Welded sensor beads, tough Kapton insulation, 5 ft. leads. Max. Temp. 400°C. Time constant 0.01 secs. Per package of six. Not isolated.   

GT-1  Air and gas probe. 24" #304 stainless steel shaft, wooden  handle. 5ft. lead. For instant readings of tempe­rature gradients in environmental chambers, freezer boxes, etc. Max Temp. 200°C. Min. Temp. –200°C. Isolated.

Clinical Probes  

RET-1   Rectal probe for humans, neonatal rabbits, and larger animals. Flexible, vinyl covered, soft tipped. Does not cause discomfort. Max. Temp. 90°C. Time constant 5.0 secs. 5 ft. lead. Isolated.  

OT-1   For fast reading oral use. Ball-tipped stainless steel shaft,  stainless handle. 5 ft. lead. Max. Temp. 125°C. Time constant 0.8 secs. Not isolated.  

DSP-1  Disposable sterile sheaths for use with OT-1 and RET-1, per 1000  

SST-1  Skin Surface probe, to be taped on.1/4" dia. 10 Kt. gold  sensor disc, 5 ft. lead. Max. Temp. 90°C. Time constant 0.15 secs. Not isolated.  

SST-2  as SST-1 with plastic handlel. Isolated.  

ESO-1  Esophageal probe. Flexible vinyl covered 1/8" dia. Max. Temp. 90°C. Time constant 5.0 secs. 5 ft. lead. Isolated.

Animal Rectal Probes  

RET-2   Rectal probe for rats. For fast intermittent measurements. Smooth ball tip. Stainless steel shaft - 1" long. 0.059" dia. Tip diameter  0.125". 5 ft. lead. Max Temp. 125°C. Time constant 0.8 secs. Not lsolated.
RET-3  Rectal probe for mice, etc. As RET-2, with shaft 3/4" long.
0.028" dia. Tip diameter 0.065". Time constant 0.5 secs. Not isolated.  

Time constant is defined as the time required to reach 63% of final temperature in liquid. An accurate reading is obtained when the reading stops changing, typically 5-10 time constants.  

Maximum Temperature refers to intermittent use of a probe. When probe is used for continuous measurements, max. temp. should be reduced by 25% unless specified.  

                                                            

Microprobes

Type           Dia.               Time 
                                      Constant  
MT-23     23 ga (.25”)    .15   secs
MT-26     26 ga (.18”)    .1     secs
MT-29     23 ga (.13”)    .025 secs

Needle Microprobes 
Fast-response needle probes for instant readings in tissue, semi-solids, liquids. Also for very small specimens, powders and materials. Needle tip is sealed to ensure only stainless steel contacts specimen. Max. Temp. 200øC. SFT. lead. Smallest microprobes give fastest reading. Short probes  are easier to insert and last longer. Type #'s indicate needle gauge and needle length in cm.

Sizes Available (ga/cm,): MT-29/1, MT-29/2, MT-29/3, MT-29/5  MT-26/2, MT-26/4, MT-26/6 MT-23/3, MT-23/5, MT-23/8

MT – 4   Similar to MT-29/1 but has blunt tip. Good for instant skin and surface temperatures, liquids. Time constant  0.025 secs. Not isolated. All above probes are non-isolated. Isolated versions of 23 ga. and larger needles are available for special order.  

Flexible Implantable Microprobes 
IT Series - Implantable in semi-solids and tissue with needle (supplied).Also for immersion in various solutions and rectal temperatures of small animals. Totally sheathed in chemical resistant Teflon™. Quite rugged. Max. Temp. 150°C. lsolated. Type # designates needle gauge (or one gauge smaller in thin wall).
Type            Dia.          Time Constant        Lead Length                                      
MT-23      23 ga (.25”)      .15   secs                     3 ft.
MT-26      26 ga (.18”)       .1     secs                    3 ft.
MT-29      23 ga (.13”)       .025  secs                   1 ft

IT-23 - For ultra fast measurements and for use on micro-size specimens.  
Max. diameter at tip 0.011". Tissue implantable with 23 ga. needle (supplied). Rather fragile. Max. Temp. 150°C. Time constant 0.005 secs. 3 ft. lead. Teflon™ coated. lsolated. - For ultra fast measurements and for use on micro-size specimens.  
Max. diameter at tip 0.011". Tissue implantable with 23 ga. needle (supplied). Rather fragile. Max. Temp. 150°C. Time constant 0.005 secs. 3 ft. lead. Teflon™ coated. lsolated.

IT-IE - As IT-18 but sensor bead exposed. Combines the ultra-fast response of IT-23 with the Teflon™ sheath strength of IT-18. Time constant .005 secs. lsolated.

MT-D - Fast response surface probe for locating inflammation, arteries,  etc. Also for dental use. Stainless steel. 5 ft. lead. Max. Temp. 200°C. Time constant 0.025 secs. Not isolated.

ICT-4 - For use on integrated circuits and other micro specimens. 0.013"  dia. straight stainless steel shaft; slightly protruding sensor bead to facilitate temperature probing. 5" tubular handle fits micro-manipulators. Max. intermittent temp. 200° C, continuous use 100°C. Time constant 0.025  secs. 5 ft. lead. Not lsolated.

MT-29/1B - Insect Probe Similar to MT-29/1 but sensor is swaged into  tip for max heat transfer. Designed for high accuracy on extremely small specimens such as insects, seeds, etc. Max. insertion depth 1/8" Time constant 0.015 secs. 5 ft. lead. Max. Temp. 150°C. Other sizes made to special order. Not isolated.

Probe sterilization Methods Physitemp's needle microprobes, clinical probes and animal rectal probes are all designed to withstand sterilization by ETO gas and gluteraldehyde solution. Our flexible implantable microprobes are both ETO gas sterilizable and autoclavable.  

          ¤ Up to 10 sensors in one probe 

           ¤ Use to profile temperature of tumor or other tissue

           ¤ Conform to NIST standards   

Physitemp multisensors are made with our specially manufactured thermocouple wire. We test and grade this wire to standards better than the accepted "Special Limits of Error" and guarantee 0.1°C accuracy in the range of 0-50°C. All multisensor probes conform to NIST standards. These multisensor probes are custom made and should be ordered to your requirements on number of sensors and spacing between sensors.

Most common applications have been for  cancer hyperthermia, where tissue temperature is an important clinical variable.

Physitemp use two different design techniques for  the manufacture of the 1T Series Flexible teflon probes. Each method has advantages :

In METHOD A, two individual wires (one  copper, one constantan) are used for each sensor. Sensors can be as close as 5 mm apart.

In METHOD B, a single common constantan wire is used. Separate copper wires are then connected to different points along the constantan wire to form the sensors. With this method, the probe can be made at least one gauge thinner and errors due to wire conduction are reduced. Sensors must be no closer than 5 mm apart.  

Multisensor needle probes can be made  with either isolated or non-isolated sensors. Please specify when ordering.

Note: Probe length is 60" maximum. Shorter lengths can be made. To extend to  distance between probe and readout, order 6 foot extension lead EXT-6 .  

1T Series Flexible Teflon®  Probes 

Teflon® sheathed thermocouple wires are implanted with regular hypodermic needle 14ga. or 17ga.  
When ordering, specify: Probe series (IT), needle gauge, number sensors and distance between sensors. We can put up to 10 sensors in a IT series probe.  

e.g. MT-2315(2)1 is a 23ga needle, 5cm long with 2 sensors -isolated. Unless otherwise specified, sensors will be 1 cm apart, starting at tip.