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众所周知 ,环境温、湿度的变化 ,可对精密仪器性能的稳定性产生影响 ,通常这种影响不会太大 ;但是当某些元器件损坏时 ,温度和湿度的变化就有可能导致仪器发生故障。我院有 1台LBY -N6型旋转式血液粘度计 ,在工作室中配备了空调 ,测试结果一直很稳定。但是最近发现该机在不使用空调时 ,每份标本的检测结果均明显高于正常值。而使用空调一段时间后 ,再对同一批标本重新测试 ,结果却归于正常。遇到这种现象 ,通常怀疑是电器元件的热稳定性不好 ,当环境温度发生变化时致使仪器发生故障。为了找到故障源 ,遂开空调 ,待测试结果正常后 ,用电吹风对电源板和每块控制板进行逐个加热 ,却未能诱发该故障 ,测试结果一直非常稳定。由此断定此故障不是因温度的变化引起的 ,而很可能是由空调暂停工作致使湿度变大造成的。经分析该仪器的工作原理可知 ,电源的输出稳定与否 ,对测试结果有很大的影响。于是打开电源单元的外壳 ,经仔细观察发现R3电阻的外层漆膜已部分脱落。从线路板上焊下该电阻 ,测得其阻值为 110kΩ ,当向其呵气后 ,阻值很快由110kΩ降至 70kΩ左右 ,显然正是该电阻在湿度变化时发生的阻值变化 ,导致了测试结果的偏差。更换新品 ,故障消失。由此可见 ,仅仅是由于电阻漆膜的脱落 ,而使其阻值在湿度增大?
As we all know, changes in ambient temperature and humidity can affect the stability of the performance of precision instruments. Usually, this effect will not be too great; however, when some components are damaged, changes in temperature and humidity may cause the instrument to malfunction. . Our hospital has a LBY-N6 rotary blood viscometer, equipped with air conditioning in the studio, and the test results have been very stable. However, it was recently discovered that the test results of each specimen were significantly higher than normal values when air conditioners were not used. After using the air conditioner for a period of time, the same batch of specimens was retested, but the result was normal. When this type of phenomenon is encountered, it is generally suspected that the thermal stability of the electrical components is not good, causing the instrument to malfunction when the ambient temperature changes. In order to find the source of the fault, the air conditioner was turned off. After the test result was normal, the power board and each control board were heated one by one by the hair dryer, but the failure could not be induced and the test result was very stable. It was concluded that this failure was not caused by a change in temperature, but it was probably caused by a temporary increase in humidity caused by the suspension of the air conditioning. The analysis of the working principle of the instrument shows that the output of the power supply is stable or not, which has a great influence on the test results. Then the casing of the power supply unit was turned on. After careful observation, it was found that the outer paint film of the R3 resistor had partially fallen off. The resistance was soldered from the circuit board and its resistance was measured to be 110kΩ. When it was swelled, the resistance quickly dropped from 110kΩ to about 70kΩ. Obviously, it was the change in resistance that occurred when the humidity changed. Caused the deviation of the test results. Replacement of new products, the fault disappears. It can be seen that, due to the falling off of the resistance paint film, its resistance value increases in humidity.