Thermometer interpolation error

Because the number of each thermal resistance is not large, and because the drift value is not constant for a long time, the bits in Table 6 are not very accurate. But from these values, it can be seen that if a suitable interpolation procedure is used, The measurement accuracy can be better than 0,1K for a long time, and only a few retests are required. In order to illustrate what kind of effect can be achieved with these simpler thermal resistances, let's talk about the use of them to transfer the silver body index of black body cavity.

If the thermocouple is to be replaced by an optical pyrometer and a resistance thermometer in the future temperature scale, the resistance thermometer and the optical pyrometer must be transferred to each other. The resistance thermometer uses a vertical metal fixed-point furnace, and in our laboratory, the optical pyrometer uses a horizontal black body furnace. Our laboratory has always used a special sodium heat pipe black body cavity to transfer these two systems The experiment on this aspect has a special article in this seminar that detailedly states that the insertion tube of the resistance thermometer is placed horizontally, and it deforms after being used for many times, so only a very thin thermometer can be inserted. The Heraeus 2515 thermal resistance was installed in the manner described in (2). During the assembly process, it was annealed at 900 ° C for 64h. In the thermometer we can obtain, other than this article, nothing can be put into this device. Throughout the experiment, the thermometer was subjected to a total of 86 hours at the silver point (962 ° C), and a total of 25 cycles were performed from 960 ° C to room temperature.

Four resistance measurements were made at Silver Point. The drift between these 4 measurements is estimated by the division of 0 ° C, 100 ° C and the zinc point (if possible); the resistance value of the freezing point increases by 0,00007 ohms per hour for the thermometer at 960 ° C for 1h After 1 cycle, the freezing point resistance increased by 0,0001 ohms, thereby interpolating. After the first blackout measurement, Zeng had considerable instability. In addition to this, other characteristics of the thermometer are satisfactory. Use the temperature of the silver point to calculate the resistance value of a certain division, and then calculate the temperature corresponding to the resistance value at the next division. The deviation of the calculated temperature value from the temperature of the silver point is a measure of the drift error of the thermometer. After 9h at 960 ℃ (including 7 cycles, without zinc point indexing), the drift error is mostly 0.088K. The deviation between the two silver points is mostly less than 0.03K. When comparing optical pyrometers, we estimated the drift, and the total error (the drift of the thermometer plus the index error of the silver point) was estimated to be less than 0.03K.

To improve this kind of measurement is possible, you can choose a stable from a batch of thermal resistance, and improve the specific measurement method, from which it can be estimated that the endogenous error of such measurement is expected to reach 0,02K. Unless it can be produced A reliable standard resistance thermometer is provided, otherwise, when any improved temperature scale is to be transferred to the work place, this 0.02K is the limit.