Thermocouple Sensors - Custom Built Thermocouples to your Specifications
We are one of the largest manufacturers of thermocouple sensors in Australia. Having an enormous range of components in stock means we can make virtually any sensor you specify. We can ship custom built thermocouples typically within 5 days or sooner.
Mineral Insulated Thermocouple Sensors
Rugged sensors, ideal for most applications. Vast choice of terminations e.g. pot seals, cables, connectors, heads etc.
Swaged Tip Thermocouple Sensors
Fast response thermocouples ideal for industrial and other applications.
Ideal for precision temperature measurements where minimal displacement and a fast response is required.
Heavy Duty Thermocouples
For industrial applications such as furnaces, kilns, ovens, boliers, flues etc. Many types of sheath material available.
High Temperature Thermocouple Sensors
Various thermocouples specifically for high temperature applications. Wide choice of sheath materials and terminations.
General Purpose Thermocouple Sensors
A wide range of thermocouples to suit many applications. Hand held, surface, bayonet, bolt, patch styles etc.
AMS2750 Approved Thermocouples
Calibrated thermocouples designed to meet the high quality and accuracies demanded for heat treatment and vacuum furnace applications
Industrial Vacuum Thermocouples
Ceramic sheathed calibrated thermocouples designed specifically in vacuum furnace applications with very low leak rates
ATEX/IECEx Approved Thermocouples
A large range of thermocouples with a variety of terminations such as pot seal, terminal heads etc.
Thermocouples - How does a Thermocouple work?
If there is a temperature gradient in an electrical conductor, the energy (heat) flow is associated with an electron flow along the conductor and an electromotive force (EMF) is then generated in that region. Both the size and direction of the EMF are dependent on the size and direction of the temperature gradient itself as well as on the material forming the conductor. The voltage is a function of the temperature difference along the conductor length. This effect was discovered by TJ Seebeck in 1822.
Temperature related EMF
The voltage appearing across the ends of the conductor is the sum of all the EMFs generated along it. For a given overall temperature difference, T1-T2, the gradient distributions shown in figures 2.1 a, b and c produce the same total voltage, E. As long as the conductor has uniform thermoelectric characteristics throughout its length.
The output voltage of a single conductor as shown, is not however normally measurable since the sum of the internal EMFs around a completed circuit in any temperature situation is zero. So, in a practical thermocouple sensor, the trick is to join two materials having different thermoelectric EMF/temperature characteristics in order to produce a usable net electron flow and a detectable net output voltage.
Thus, two connected dissimilar conductors, A and B, exposed to the same temperature gradients given in figure 2.1 generate outputs as shown in figure 2.2. Basically, there is a net electron flow across the junction caused by the different thermoelectric EMFs, in turn resulting from the interaction of the gradient with the two different conductors. Hence the term, 'thermocouple'.
It is worth noting that the thermoelectric EMF is generated in the region of the temperature gradient and not at the junction as such. This is an important point to understand since there are practical implications for thermocouple thermometry. These include ensuring that thermocouple conductors are physically and chemically homogenous if they are in a temperature gradient. Equally, the junctions themselves must be in isothermal areas. If either of these conditions is not satisfied, additional, unwanted EMFs will result.
Incidentally, any number of conductors can be added into a thermoelectric circuit without affecting the output, so long as both ends are at the same temperature and that homogeneity is ensured. This leads to the concept of extension leads and compensating cables, enabling probe conductor lengths to be increased. See Part 2, Section 3.
Returning to figure 2.2, in fact the output, ET, is the same for any temperature gradient distribution over the temperature difference T1 and T2, provided that the conductors again exhibit uniform thermoelectric characteristics throughout their lengths. Since the junctions M, R1 and R2 represent the limits of the EMF-generating conductors, and since the remaining conductors linking the measuring device are uniform copper wire, the output of the thermocouple is effectively a function only of the two main junctions’ temperatures. In essence this is the basis of practical thermocouple thermometry.
Measuring and Reference Junctions
The relevant junctions are the so-called measuring junction (M) and the junction of the dissimilar wire to the copper output connections (usually, a pair of junctions), called the reference junction (R), as in Figure 2.2. So long as the reference junction (R) is maintained at a constant, known temperature, the temperature of the measuring junction (M) can be deduced from the thermocouple output voltage. Thermocouples can thus be considered as differential temperature measuring devices - not absolute temperature sensors.
There are important points to note at this stage. Firstly, thermocouples only generate an output in the regions where the temperature gradients exist, not beyond. Secondly, accuracy and stability can only be assured if the thermoelectric characteristics of the thermocouple conductors are uniform throughout. Finally, only a circuit comprising dissimilar materials in a temperature gradient generates an output.
Mineral Insulated Thermocouples
Thermocouple with Basic End Seal 0.25 to 10.8mm dia.
Internal seal with bare conductors
Thermocouple with Pot Seal 0.25 to 10.8mm dia.
a large selection of plain and threaded pot seals supplied with tails or extension cable (PVC, FEP, Fibreglass etc.)
Thermocouple with Miniature Plug 0.25 to 3.2mm dia.
fitted with a miniature thermocouple plug rated to either 220ºC, 300ºC, 425ºC or 600ºC
Thermocouple with Miniature Socket 0.25 to 3.2mm dia.
fitted with a miniature thermocouple socket rated to either 220ºC, 300ºC, 425ºC or 600ºC
Thermocouple with Standard Plug 1.5 to 8.0mm dia.
fitted with a standard thermocouple plug rated to either 220ºC, 300ºC, 425ºC or 600ºC
Thermocouple with Standard Socket 1.5 to 8.0mm dia.
fitted with a standard thermocouple socket rated to either 220ºC, 300ºC, 425ºC or 600ºC
Thermocouple with Lemo Connector
3.0 to 6.0mm dia.
fitted with a size 1 Lemo plug
Thermocouple with Terminal Entry Gland
1.0 to 8.0mm dia.
terminated with a 16mm ISO x 1.5mm compression gland seal supplied with tails or extension cable (PVC, FEP Fibreglass etc.)
Thermocouple with Micro die cast alloy head 3.0 to 6.0mm dia.
Micro die cast alloy screw down terminal head with ceramic terminal block. Suitable for simplex and duplex assemblies
Thermocouple with Miniature IP67 die cast head 3.0 to 8.0mm dia.
Weatherproof die cast alloy screw top terminal head with ceramic terminal block. Suitable for simplex and duplex assemblies
Thermocouple with Standard IP67 die cast head 4.5 to 10.8mm dia.
Weatherproof die cast alloy screw top terminal head with ceramic terminal block. Suitable for simplex, duplex and triplex assemblies
Thermocouple with IP67 heavy duty cast iron head 4.5 to 10.8mm dia.
Weatherproof cast iron screw top terminal head with ceramic terminal block. Suitable for simplex, duplex and triplex assemblies
Thermocouple with IP67 Bakelite head 4.5 to 10.8mm dia.
Weatherproof Bakelite screw top terminal head with Bakelite terminal block. Suitable for simplex, duplex and triplex assemblies
Thermocouple with alloy straight through head 4.5 to 10.8mm dia.
Die cast alloy straight through terminal head with Bakelite terminal block. Suitable for simplex and duplex assemblies
Thermocouple with 316 Stainless Steel head 4.5 to 10.8mm dia.
Weatherproof 316 stainless steel screw top terminal head with ceramic terminal block. Suitable for simplex and duplex assemblies
Thermocouple with BUZ-H style top hat head
4.5 to 10.8mm dia.
Weatherproof die cast alloy screw down 'flip' terminal head. Mainly used for duplex assemblies where two transmitters can be fitted
Thermocouple with spring loaded terminal block 3, 4.5, 6 and 8mm dia.
Spring loaded insert assemblies. The end seal is incorporated into a terminal block for mounting into any standard terminal head