Thermal converter is a device that is designed to measure temperature. The principle of operation of this device is based on the electrical resistance of metals and individual alloys. Semiconductors are considered to be the main element of thermal converters. Some experts call them thermistors.
If we consider a standard thermal converter, then it has only one resistor. It is made entirely of metal wire. In some cases, it can be made from film. Platinum thermal converters are by far the most common. This is due to the fact that this metal has a good dependence of resistance on temperature. Platinum is also highly resistant to oxidation. The reproducibility of thermal converters of this type is quite high.
Modern models are made from high purity platinum. In this case, the temperature coefficient of the metal is 0.003. However, there are many copper and nickel devices on the market. All technical requirements for themdictated by GOST. In frequency, this system of uniformity of measurements gives temperature ranges, accuracy classes and standard resistance dependencies.
Two-wire modifications
For operation in gaseous medium, a two-wire resistance thermocouple is used. The scheme of its device is quite simple. In the upper part there is a sensitive element with a conductor. It connects with a fitting. There are clips and a cable at the bottom of the case. The error at sub-zero temperatures for models does not exceed 0.3 degrees.
If we talk about the design features of the models, it is important to note that they are produced with a sealant. There are usually two conclusions. The clips are directly installed in the front of the case.
Three-wire thermal converters
Three-wire RTD is excellent for liquid applications. However, the minimum temperature parameter for models is on average -30 degrees. It is also important to note that the error in an aggressive environment can reach up to 0.45 degrees. There are two outputs in devices of this type. There is a direct tolerance according to GOST 6651 series A. The indicator of the minimum allowable temperature fluctuates around 230 degrees.
If we consider the resistance temperature converter TC 1088, thenthe length of its mounting part reaches 100 mm. If we talk about modifications with a terminal head, then they have three outputs. Protective fittings are used with marking 12X. The thermal inertia indicator can reach up to 10 s. In turn, the parameter of the maximum conditional pressure is on average 6.2 Ru. Resistance thermocouples are checked using temperature calibrators.
Four-wire devices
A four-wire resistance thermocouple is designed to measure temperature in a liquid medium. If we talk about the resistance error, then this parameter can reach up to 0.03 Ohm. In this case, the sensitivity of the devices is on average 33 microns. If we talk about modifications with A tolerance, then the minimum temperature at which they are able to work is 30 degrees below zero. The nominal static characteristic of the devices reaches 100 MP. Protective fittings in many modifications are used with the marking 12X.
If we consider the DTS 105 resistance temperature converter, then the maximum temperature indicator is 230 degrees. The permissible deviation limit is no more than 0.15 T. It is also important to note that devices of this type are produced with terminal heads. Insulation in them is used only ceramic. In this case, the clamps are installed in the front of the case. If we talk about sensitivity, then these devices have a maximum of 32 microns.
Platinum mods
The platinum resistance thermal converter (PTTC) boasts excellentindicator of thermal inertia. However, in this case, it is important to take into account the tolerance of the model according to GOST 6651. If we consider modifications of the A series, then in this situation the nominal static characteristic of the devices does not exceed 50 P. The thermal inertia indicator, in turn, is 10 s.
Maximum temperature resistance thermocouple (platinum) series A is able to endure 240 degrees. Protective fittings for models are most often used with the marking 12X. If we consider with the tolerance of series B the resistance temperature converter (GOST 6651), then its nominal static characteristic parameter is 100 P. The thermal inertia indicator, in turn, reaches 25 s.
Copper devices and their parameters
Thermistor (copper) is only suitable for gaseous media. In terms of the modification error parameter, they are quite different. First of all, you need to consider thermal converters with a series A approval. They are used even at temperatures as low as -50 degrees. However, their sensitivity is not very good. This parameter does not exceed 34 microns on average. All this suggests that at temperatures below 0 degrees, the average error is 0.5 degrees.
Indicator of thermal inertia, in turn, reaches 10 s. In this case, the maximum possible temperature for models is 230 degrees. The permissible limit of deviations in this case reaches 0.12 T. If we talk about design features, then the terminal heads for models of this typemissing. Sealant in many configurations is used with powder. Directly insulators are often used silicon type. If we consider thermal converters with B series approval, then they have a sensitivity of 40 microns. All this suggests that at temperatures below 0 degrees, the error can reach up to 0.45 degrees.
Considering the design features of modifications, it is important to note that many models are equipped with terminal boxes. In this case, the sealant is usually applied with powder. The clamps are directly installed in the front of the case. Protective fittings are most often used with the marking 15X.
Nickel devices
Nickel resistance thermal converter is in high demand today. First of all, this is due to the fact that the models have a high parameter of permissible marginal deviations. Also, many modifications can boast excellent conductivity. If we consider devices with a tolerance according to GOST 6651 series A, then it is important to mention that their error parameter does not exceed 0.23 degrees. The permissible limit of deviations, in turn, is at the level of 0.12 T.
The nominal static characteristic of models is on average 30 P. However, it is also important to consider modifications with access to the B series. They have protected cases, and they can withstand a maximum temperature of 230 degrees. The length of the mounting part of the models on average does not exceed 100 mm. If we talk about the main parameters, it is important to mention that the sensitivity of devices on averageis 35 microns. The maximum conditional pressure by the system is maintained at 6.6 Ru. The thermal inertia parameter never exceeds 13 s.
High temperature models
High temperature RTD can be produced with different tolerances. Depending on it, the error parameter will change, and other indicators of the device. If we talk about access series A, then thermal converters of this type have a high nominal pressure. At least the devices can be used at a temperature of -30 degrees. The cases of these devices are well protected from dust. The permissible error limit of the device does not exceed 0.12 T. The sensitivity, in turn, is 33 microns.
The nominal static characteristic of thermal converters is 40 P. However, it is also important to consider modifications with B-series access. According to GOST 6651, their sensitivity index must be at least 20 microns. At temperatures above 0 degrees, the instrument error does not exceed 0.44 degrees.
If we talk about the design features of the models, then the clamps are installed in the front of the case. Directly the head is located at the top of the device. There are two conclusions in total. It is also important to mention that this type of thermal converters are equipped with ceramic thermal insulation.
Features of submersible modifications
The immersion temperature converter must be equipped with a terminal box. The cable cores of many models are hidden with a sheath. The clamps in this case are located at the bottom of the case. The parameters of the product are directly related to the access series in accordance with GOST 6651. However, it should be noted right away that the immersion thermal converter can be operated in aggressive environments. If we consider modifications with a series A approval, then the sensitivity of the device in this case does not exceed 42 microns. The error in this case is 0.02 degrees. However, it is important to consider that the thermal inertia indicator will never exceed 10 s.
The nominal static characteristic of submersible devices is 50 P according to GOST 6651. There are two outputs in the presented thermal converters. It is also important to consider models with B-series access. First of all, the high sensitivity parameter deserves attention - at the level of 30 microns. All this makes it possible to reduce the instrument error to 0.023 degrees. The maximum temperature of the medium in this case should not exceed 240 degrees. The length of the mounting part of the models is on average 85 mm. Directly protective fittings are used with the marking 12X. The thermal inertia index for thermal converters does not exceed 3 s.
Explosion proof models
Thermal converter of this type is designed to work in a gaseous medium. In this case, the terminal heads are used with a fitting. The maximum temperature devices are able to withstand at the level of 250 degrees. The thermal inertia index is closely related to the access seriesdevices. However, it is important to note that all models withstand the maximum nominal pressure at the level of 6.7 Ru. If we consider devices with A-series access, it is important to mention that the error at temperatures above 0 degrees is 0.035 degrees.
The terminal head in these configurations is mounted on top of the housing. The directly nominal static characteristic of thermal converters does not exceed 60 P. The permissible deviation limit of the device is on average 0.20 T. It is also important to consider thermal converters with access to series B. They have three conclusions. Direct insulation is applied ceramic type. As mentioned earlier, the maximum conditional pressure is maintained at the level of 6.7 Ru. At least models can be operated at a temperature of -30 degrees.
The sensitivity of devices does not exceed 40 microns. The error at temperatures above 0 degrees is approximately 0.040 degrees. The nominal static characteristic of the devices is 40 P. The mounting part of the models does not exceed 80 mm. The thermal inertia parameter in the devices is quite high. However, the allowable deviation limit is only 0.33 T.
Error TSP-0196-01
Resistance thermocouple TSP 0196-01 is designed for liquid media. According to GOST 6651, it has a series B approval. The minimum temperature of the medium is -35 degrees. The nominal static characteristic of the device does not exceed 50 P. If we consider modifications with terminal boxes, then the lengththeir mounting part is 85 mm. The protective fittings of the model will be used with the marking 13X. The indicator of thermal inertia of the device is at the level of 15 s. In turn, the maximum temperature is 240 degrees.
The permissible limit of deviations on average does not exceed 0.15 T. At temperatures above 0 degrees, the resistance thermocouple TSP 0196-01 gives an error of 0.033 degrees. The terminal box configuration has three terminals. In this case, the sensing element is located in the front of the housing. Direct insulation is provided by the manufacturer of the ceramic type. The sealant, in turn, is applied with the powder. Thus, the case is quite well protected, and this model rarely has problems with metal oxidation.
Model TSM-0196-02
Resistance thermocouple ТСМ 0196-02 is designed to operate in a liquid medium. It is distinguished by good conductivity and a high maximum temperature parameter. However, first of all, it should be noted that it has series A approval according to GOST 6651. In this case, the minimum temperature indicator is -50 degrees.
For laboratory research, the presented copy is used quite often. At temperatures above 0 degrees, its error is no more than 0.045 degrees. The nominal static characteristic of the device is about 55 P. The mounting part of this model is 85 mm. Directly protected rebar is used with 12X marking.
The maximum temperature parameter is at around 250degrees. There is no terminal box in the specified configuration. The manufacturer provides two conclusions. Metal oxidation problems are quite rare since sealing is used with powder. The isolation in this case is reliable.
Thermal converter TSP-0196-06
Thermal converter of this type is quite in demand in the production of fusible metals. In this case, protective fittings are provided for 15X. Directly approved according to GOST 6651, the model has series B. The minimum temperature of the medium is -30 degrees. The high sensitivity parameter deserves special attention. However, it should be noted that at temperatures above 0 degrees, the error of the thermal converter is 0.022 degrees.
The length of the mounting part of the model is only 60mm. The indicator of thermal inertia is at around 12 s. The maximum allowable ambient temperature at which the device can be used is 240 degrees. A terminal head is provided for this thermal converter.
