An electric soldering iron thermometer is composed of a temperature sensing wire and an instrument.
If you have a digital multimeter in your hand that can measure temperature, and the probe is a thermocouple, it would be very convenient. Because this thermocouple is usually K-type, simply connect the output of the temperature sensing wire to the temperature input of the multimeter! The temperature will be displayed directly.
If the digital multimeter in hand cannot measure temperature, then it can only use its 200mV range to measure voltage, then check the meter and convert it into a temperature value.
The temperature sensing line can be measured using a white light 191 thermometer, and only one line is needed. The temperature sensing wire is a consumable material that needs to be replaced after about 50 uses to ensure accuracy, so it is easy to buy.
The temperature sensing wire is the trademark of Mercedes Benz, with a temperature sensing block in the middle leading out three wires, and a circle at the end used to connect to the terminal block. In fact, it is made of two wires, with the positive wire covered in red and the negative wire covered in blue. There is also an edge where these two wires are intertwined and not used as a signal wire. It is mainly used as a support because only three edges can support it firmly.
My main job is to make a frame for the temperature sensing wire.
Buy 3 terminal blocks. When the thread of the terminal is larger than the circle of the temperature sensing wire lead, remove the small circle of the lead, and then re wrap a large circle according to the thread size of the terminal.
Take another waste circuit board and compare the dimensions. Use an electric drill to drill three holes, which are exactly a triangle, and install the wiring terminals on the circuit board. Connect the three pins of the temperature sensing wire to the threads of each terminal and tighten the nut. Just solder it online and connect it to the multimeter. As shown in the figure:
When measuring temperature, the soldering iron head should first be tinned and then placed on the temperature sensing block in the middle of the temperature sensing line. The tinned surface should be in horizontal contact with the temperature sensing block and have a certain amount of force. The temperature sensing block can be tinned, so it can fully contact the soldering iron head and measure the temperature accurately. At this point, the temperature measurement range of the multimeter directly displays the temperature.
If the measured voltage is mV, use the following conversion table to convert the voltage to temperature, plus room temperature, to obtain the temperature of the soldering iron tip. For example, 12.6mV is 310 ℃, and with room temperature such as 30 ℃, the temperature of the soldering iron head is 340 ℃.
In addition, it is possible to directly contact the soldering iron head with the thermocouple of a multimeter without using a temperature sensing wire. However, the thermocouple of the multimeter is not soldered, so it cannot fully contact the soldering iron head and may be slightly lower than the temperature value measured by the temperature sensing wire, but generally only about 2-5 ℃.
PS: When I first made this temperature sensing wire, I was mainly worried that the thermocouple of the multimeter would directly measure the soldering iron head, which would be very inaccurate, and there would be a difference of several degrees. However, now I have finished and found that it is still quite accurate, only a few degrees difference.
