一是直接用双金属片控温，简单的说就是在螺栓加热棒内部放置一个双金属片，应为双金属片的两面用的是不同的材料，受热膨胀系数不同，利用这点就可以在达到你所设定的温度自动断开了，优点是构造简单，价格低廉，工作可靠性比较高。一般正规厂家生产的和假冒伪劣商品的区别很大一部分就是在这个地方了，假货采用的是劣质的东西，使用一段时间后容易发生疲劳了，造成在设定的温度不跳开，造成不可挽回的结果。缺点就是，不管哪种材质的双金属片，都有一个老化期，所以我在上面建议大家在用2年就可以换一个了。

One is the direct use of the bimetal temperature control, simply put a double sheet metal bolt in the heating rod inside, should be on both sides of the double metal sheet with different materials, thermal expansion coefficient is different, the use of which can be reached in your set temperature automatically disconnected, has the advantages of simple structure work, low price, high reliability. General formal manufacturers and fake and shoddy goods difference is a large part in this place, the poor thing is fake, after a period of time prone to fatigue, caused by the jump in the set temperature, causing irreversible results. The drawback is that no matter what kind of bimetallic, there is an aging period, so I suggest that you can change it in 2 years.

二是采用热敏电阻探测温度，用可控硅等来控制加热棒的通断。

The two is to use the thermistor to detect the temperature, and to control the opening and breaking of the heating rod by using SCR and so on.

1）热敏电阻和加热棒在一体的，这种的优点就是安装比较方便，没有太多的线，看起来比较好看。缺点也正是由于热敏电阻和加热棒距离比较近，往往造成加热棒内部温度实际上已经达到设定温度了，而鱼缸内水温确没有达到所设定的稳度，大家从平时的使用中就可以看到，加热棒一般是加个一会就停了，然后过一会有开始加温了。

1) the thermistor and the heating rod in one, this advantage is that the installation is more convenient, there are not too many lines, it looks better. The shortcomings is due to thermal resistance and heating rod distance, often caused by the internal temperature of the heating rod has actually reached the set temperature, water temperature and fish do not achieve the desired stability, we can see from the usual use, the heating rod is generally a stopped for a moment, and then after a while there is a heated.

2）热敏电阻和螺栓加热棒不是在一体的，这种的优点是，加温比较快，可以把热敏电阻和加热棒分别放到距离比较远的地方，这样正好克服了上面1）中的缺点。但是他的缺点也很明显，首先是多出一根热敏电阻的线，看起来不舒服，在就是万一热敏电阻不小心被你从鱼缸里弄出来了，呵呵，这样任你在怎么样的加温，他也检测不出来了。

2) the thermistor and the bolt heating rod are not integrated. This advantage is that the heating is faster, and the thermistors and the heating rods can be placed at a distance away from each other, which overcomes the shortcoming in the above 1. But his shortcoming is also very obvious. First of all, there is a thermistor wire. It looks uncomfortable. It's just that if the thermistor is carelessly caught by you from the fish tank, you can't detect it when you are warming up.