What is a DIY soldering iron thermometer?
The soldering iron thermometer is composed of temperature sensing wire and instrument.
It would be very convenient if you have a digital multimeter on hand that can measure temperature and the probe is a thermocouple. Because the thermocouple is generally K-type, just connect the output of the temperature sensing wire directly to the temperature input of the multimeter! The temperature is displayed directly.
If the digital multimeter in hand cannot measure the temperature, then you can only use its 200mV range to measure the voltage, then look up the meter and convert it into a temperature value.
You can use a white light 191 thermometer as the temperature sensing wire. You only need to use one. The temperature sensing wire is a consumable material and needs to be replaced after about 50 uses to ensure accuracy, so it is easy to buy.
The temperature sensing wire is in the shape of Mercedes-Benz's trademark. There is a temperature sensing block in the middle, leading to three wires, and a loop is made at the end to connect to the binding post. It is actually made of two wires. The one with the red cover is the positive wire, and the blue cover is the negative wire. There is also an edge where these two wires are entangled together. It is not used as a signal line, but is mainly used as a support, because there are three wires. The edge can be supported firmly.
The main job is to make the frame for the temperature sensing wire.
Buy 3 binding posts. If the thread of the terminal is larger than the loop of the lead wire of the temperature sensing wire, remove the small loop of the lead and then make a larger circle according to the thread size of the terminal.
Take another scrap circuit board, use an electric drill to drill three holes of a good size, exactly in the shape of a triangle, and install the binding posts on the circuit board. Then connect the three legs of the temperature sensing wire to the threads of each terminal and tighten the nuts. Then solder the wire to the multimeter and you're good to go. As shown in the picture:
When measuring the temperature, first put some tin on the soldering iron tip, and then place it on the temperature sensing block in the middle of the temperature sensing line. The tin surface should be in horizontal contact with the temperature sensing block and have a certain degree of strength. The temperature sensing block can be tinned, so it can fully contact the soldering iron tip, and the measured temperature is relatively accurate. At this time, the temperature measurement setting of the multimeter directly displays the temperature.
If the voltage mV value is measured, use the following conversion table to convert the voltage into temperature. Add the room temperature to the temperature of the soldering iron tip. For example, 12.6mV is 310℃, plus room temperature, such as 30℃, the temperature of the soldering iron tip is 340℃.
In addition, it is possible to directly use the thermocouple of a multimeter to contact the soldering iron tip without using a temperature sensing wire. However, the thermocouple of the multimeter is not tinned, so it cannot fully contact the soldering iron tip, and the temperature value measured by the temperature sensing wire will be slightly lower. , but generally only about 2-5℃ smaller.
