DIY electric soldering iron thermometer
The electric soldering iron thermometer is composed of a temperature sensing wire and an instrument.
If you have a digital multimeter that can measure temperature and the probe is a thermocouple, it would be very convenient. Because usually this thermocouple is also K-type, simply connect the output of the temperature sensing line to the temperature input of the multimeter! It directly displays the temperature.
If the digital multimeter in hand cannot measure temperature, then it can only use its 200mV range to measure voltage, and then check the meter to convert it into temperature value.
The temperature sensing line can be used with a white light 191 thermometer, as long as one is used. 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 purchase.
The temperature sensing wire is the trademark of Mercedes Benz, with a temperature sensing block in the middle that leads out three wires, and a circle at the end for connecting to the terminal. In fact, it is made of two wires, with the red wire being the positive wire and the blue wire being the negative wire. There is also an edge where these two wires are wrapped together and not used as a signal wire. It is mainly used as a support because only three edges can support it firmly.
The main job is to make a frame for the temperature sensing line.
Buy 3 terminal posts. When the thread of the terminal post is larger than the circle of the temperature sensing wire lead out, remove the small circle of the lead out wire and then wrap a large circle according to the thread size of the terminal post again.
Take another waste circuit board, compare the size, drill three holes with an electric drill, which are exactly a triangle, and install the terminal posts 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 again and connect it to the multimeter. As shown in the picture:
When measuring temperature, the soldering iron tip 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 with a certain amount of force. The temperature sensing block can be tinned, so it can fully contact the soldering iron tip and measure the temperature accurately. At this point, the temperature range of the multimeter directly displays the temperature.
If the measured value is in mV voltage, use the following conversion table to convert the voltage to temperature, and then add the room temperature to obtain the temperature of the soldering iron tip. For example, 12.6mV is 310 ℃, and with room temperature of 30 ℃, the temperature of the soldering iron tip is 340 ℃.
In addition, it is possible to directly contact the soldering iron tip with the thermocouple of the multimeter without using a temperature sensing wire. However, the thermocouple of the multimeter is not soldered, so it cannot fully contact the soldering iron tip and may be slightly lower than the temperature value measured by the temperature sensing wire, but generally only about 2-5 ℃ lower.
pS： When I first made this temperature sensing wire, I was mainly worried that the thermocouple of the multimeter would be inaccurate when directly measuring the soldering iron tip, with a difference of several tens of degrees. However, now that I have finished it, I have found that it is still quite accurate, with only a few degrees of difference.
