At measurement of temperature in industrial conditions electric thermometers of resistance apply complete with crossed-coil instruments, automatic balanced bridges and automatic compensation devices. Thus it must be kept in mind that these devices supply with a scale, otgraduirovanny in degrees Celsius which is valid only for a certain graduation of the thermometer of resistance and a preset value of resistance of the wires connecting the thermometer to the measuring device.
From the table it is visible that the platinorody-platinum thermometers providing also the best reproducibility termo-EDS have the smallest error. The positive electrode at them shows a platinum alloy with rhodium – platinorodiya, and negative – pure platinum. Platinorody-platinovye thermometers use as reference and exemplary.
In the elementary thermoelectric chain made of two diverse conductors And and In there are four EMFs. Two arise in places of connections of conductors (they will be various as temperatures are various). Besides in each uniform conductor which ends have different temperatures, there is a potential difference.
The principle of operation of thermoelectric thermometers is based on use of tremoelektrichesky effect which is that in the closed chain consisting of two or several diverse conductors there is an electric current if at least two junctions of these conductors have different temperature.
Scales of automatic potentiometers are graduated in degrees Celsius or in millivolts. If the scale of the device is graduated in terms of temperature, on it the type of the thermoelectric thermometer is specified. Use of such device with other thermometer is inadmissible.
Recently the thermoelectric thermometers with thermoelectrodes from refractory connections or their combinations with graphite and other materials intended for measurement of high temperatures were created. However they did not gain distribution for control of temperatures of technological processes in branch yet.
also we compare this relation with maximum permissible value (the first has to be, equal 0.0, in the case under consideration the condition is satisfied therefore it is possible to consider the received calculated values found.
On the basis of the set range of temperatures of t = 0C and t = 100C as the primary measuring device (PMD) we will take the copper thermometer of resistance as use of thermoelectric thermometers I consider inexpedient in this range of temperatures, with a nominal resistance at 0C R = 53,00 Ohms. To the PIP this type there corresponds the bridge scheme of measurement used in automatic bridges.