Introduction to Thermocouple Box

Thermocouple box is a box type resistor. It is formed by several fixed-value resistors with different resistances connected in a certain way. The fixed value resistance in the thermocouple box is generally wound with constantan and manganese copper wire, so that the resistance value does not change with temperature. There are two types of thermocouple boxes for laboratory use: plug type and switch type (also called barrel type).

The thermocouple box is a variable resistance appliance that uses a conversion device to change its resistance. This kind of conversion device usually adopts a decimal disc type (knob type) structure, and can also adopt a plug type and a button type structure as required. The circuit of the thermocouple box can be divided into series circuit and series-parallel circuit.

When in use, connect the two terminals to the circuit (the two terminals are not divided into positive and negative poles), and adjust the dial to get any resistance between 0~×××××× ohms (usually 9999.9 ohms). (Usually turn the dial clockwise) The indication of each indicator point corresponding to each dial is multiplied by the multiple marked on the dial, and then added together to obtain the resistance of the connected circuit.

The indication of the indicator point corresponding to each dial is multiplied by the multiple marked on the panel, and then added together to obtain the resistance value of the access circuit. . Indicates that the resistance value of the access circuit is 1 ohm + 2 ohms = 3 ohms. There are two binding posts on its front panel and several knobs. Next to the knobs are marked with magnification ×1, ×10, ×100, ×1000, and the knobs are marked with ten numbers 0-9. When in use, the value pointed to by the mark (white dot) on the panel is multiplied by the magnification marked next to the knob, which is the resistance value of the circuit connected to the knob. The thermocouple box shown in the figure can form various integer resistance values ??in the range of 0-9999 ohms for use in experiments. As shown in the figure, the resistance value at this time is 2408 ohms.

The sliding rheostat can change the resistance of the connected circuit and play the role of continuously changing the current, but it cannot accurately know the resistance of the connected circuit. If you need to know the resistance of the resistor connected to the circuit, you need to use a thermocouple box.

The thermocouple box is a rheostat that can adjust the resistance and display the resistance value.

Compared with the sliding rheostat, the sliding rheostat cannot indicate the resistance value of the connected circuit, but it can continuously change the resistance in the connected circuit. The thermocouple box can indicate the resistance of the connected circuit, but the resistance change is discontinuous and there is no accurate change in the value of the sliding rheostat.