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  • 工业温度计热回差怎么样估计
  • 本站编辑:杭州博阳仪器仪表有限公司发布日期:2019.11.22
 对铂电阻温度计的热回差和热应力的影响进行估计,需要进行非常仔细的试验.如果怀疑温度计有热回差,就必须在试验过程中对温度计的受热过程加以控制。有意义的回差试验是在整个温度范围内对温度计进行分度,分度方法是分别按升温方向和降温方向在许多温度点跟标准铂电阻温度计比较.试验从头到尾使用同一支标准铂电阻温度计和同样的电阻测量仪器,这对于避免测量仪器误差的影响是很重要的.无论是升温还是降温,都要保证被试温度计从一个试验温度平稳地过渡到另一个试验温度,这样就能控制热过程,对同一温度点的升温和降温电阻值求平均,就得出平均的R一T曲线,本实验所使用的内插式就是标准铂电阻温度计使用的内插式,在-196℃到+196℃的温度范围,一般需要四个分度点。把每个温度试验点的电阻值与温度计平均电阻值之差折算成温度。
    这种试验方法在实际工作中有些问题。如果使用液体槽作为分度设备,那么,每一种液体都有其有限的温度范围,这个范围可能狭窄到100℃。这就是说,为了保持温度计的热过程不变,可能要把被试温度计非常迅速地从一个槽转移到另一个槽.这个转移过程也会产生微小的、但能测量出来的电阻变化,这种变化是操作时机械冲击引起的。
    用上述方法在许多不同的沮度跨度温度计元件类型进行了广泛的试验。从这种试验以及对其他不同类型的铂电阻温度计元件所做的试验看来,回差的大小是与温度跨度成正比的,大的差值出现在温度跨度的中点。还发现热回差具有很好的再现性,温度循环方式相同,产生的滞环也相同。

Estimating the effect of thermal resistance thermometer and thermal stress on platinum requires very careful testing. If a thermometer is suspected to have a return of heat, the heating process of the thermometer must be controlled during the test. The meaningful return test is the calibration of the thermometer over the entire temperature range by comparing it with the standard platinum resistance thermometer at many temperature points in the direction of warming and cooling, respectively. The use of the same standard platinum resistance thermometer and the same resistance measuring instrument throughout the test is important to avoid the effects of instrumentation errors. Whether it is heating up or cooling down, it is necessary to ensure that the temperature of the test is smoothly transferred from one test temperature to another, so that the thermal process can be controlled and the values of the heating and cooling resistances at the same temperature point can be averaged The average R T curve is obtained. The interpolation used in this experiment is the same as that used in the standard resistance thermometer. In the temperature range from-196 °C to + 196 °C, four dividing points are generally required. Convert the difference between the resistance value of each temperature test point and the average resistance value of the thermometer into temperature. There are some problems in the practical work of this test method. If a liquid tank is used as a dividing device, each liquid has a limited temperature range, which may be as narrow as 100 °C. This means that the thermometer may be moved very quickly from one slot to another in order to maintain the thermal process of the thermometer. This transfer process also produces small but measurable changes in resistance due to mechanical shock during operation. Extensive experiments have been carried out with the above methods on many different types of thermometer elements with different span. According to this and other tests on different types of resistance thermometer, the magnitude of the backlash is proportional to the temperature span, with the large difference occurring at the midpoint of the temperature span. It is also found that the thermal recovery error has good reproducibility, the same temperature cycle mode and the same hysteresis loop.
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