Chapter 135: [Metal Detector]

Convenience of circulation is indeed one of the reasons. Compared with gold coins, silver coins and copper coins are undoubtedly more suitable for use in daily life.

But this is not the main reason. The reason why Ma Shao needed more silver coins was mainly to realize an invention.

With a thousand brand new Browning revolvers and the guerrilla warfare tactics taught by Ma Shao, Chavez left Sleeping Bear City...

Ma Shao took the silver coins and first found a few bottles of nitric acid to purify the silver in the coins.

The silver content of these Spanish silver coins is not high, only about 90%. Silver coins are generally not pure silver, and often need to be mixed with some other metals, mainly to increase the hardness and make it more durable.

Then he gave the purified silver to a blacksmith and asked him to make it into silver wire and some small parts.

With these silver wires and parts, Ma Shao can officially start his invention - the metal detector.

Strictly speaking, he has invented a metal detector. After all, the principle behind this thing is not complicated. It is mainly an eddy current effect, which is content from high school physics. Of course he can make it.

But the problem was that the metal detector he had invented before was so poor in performance that at first it would only respond if you put metal on it.

It may be that the design is not good enough, or it may be that his craftsmanship is not good enough.

Of course, it is more likely that the front-end technology is a bit insufficient. The battery is an improved voltaic pile, the voltage is not stable enough, and the indicator device is a small fan, which is not very intuitive.

All in all, no matter how he improved it, the performance of the metal detector was still not satisfactory. So he finally decided to replace the wires with silver wires to see if he could improve it further.

After all, silver is the metal with the best conductivity. Although it is not much stronger than copper, it is always worth a try.

Soon he would go to California to look for gold. With a metal detector as an aid, even the most crude one would be much more efficient than using the naked eye.

Ma Shao replaced all the conductive parts in the metal detector with silver and then conducted the experiment again.

This detector is so simple and somewhat bulky. First of all, it is a square wooden box containing a voltaic pile.

There is an opening in the wooden box, and a silver wire wrapped in cowhide extends out of it and is connected to the handle. Below the handle are the indicator fan and coil.

The coil and handle are of course also mostly protected by the wooden shell, and a glass cup is placed on the indicator fan to prevent it from being affected by the flow of external air.

For ordinary people, the wooden box containing batteries may need to be carried on the back, but with Ma Shao's body size, it is enough to carry it in the hand.

In the chief's hall, there were some gold coins on the ground.

Ma Shao held the battery box in one hand and the handle in the other, slowly approaching the gold coins from a distance while observing the changes in the fan.

With his careful tuning, the fan speed is relatively stable, at least by the naked eye.

As the metal detector and the gold coins approached, the induced magnetic field generated by the gold coins changed the current in it, and the rotation of the fan also changed accordingly, first slowing down, and when Ma Shao retracted the detector slightly, the speed of the fan became faster again.

The fan would jump back and forth between fast and slow depending on the distance from the metal. Under the existing technical conditions, this was the best indicator device that Ma Shao could think of.

The accuracy is good, but the detection distance is still not far, and it can only detect metal in front of you.

It seems that this is the limit.

At this time, Rainy Day came in from outside, and immediately saw what Ma Shao was holding, and asked, "What is this?"

"Metal detector." Ma Shao said, putting the wooden box on the table and then handed the handle over. "Do you want to try it?"

Rainy Day took the handle curiously: "How do I use it?"

"Put this close to where you want to detect. If there is metal there, the speed of the fan will tell you." Ma Shao pointed to the coil of the detector.

"Is it true?" Xia Yutian asked in amazement. He picked up the detector impatiently and moved closer to the gold coins next to him.

Just as Ma Shao said, as soon as the detector approached the gold coin, the fan on it immediately began to slow down.

Around the gold coin, every change in distance will bring about a change in the fan speed, and once away from the gold coin, the fan returns to stability.

"This... this is incredible!" Rainy Day couldn't help but open his eyes wide, and then tried it with copper and iron, and found that copper and iron could also be detected by the detector.

"How did you do that?" He turned the detector over and looked at the silver wire coil that was not wrapped in the wooden shell.

"You should be able to guess that I have explained a little about its principles in the mathematics and physics advanced training class." Ma Shao said with a smile.

It was a bit of a headache on a rainy day, and it was clear that he wasn't very good at math and physics: "Is it Faraday's…law of electromagnetic induction?"

"Almost." Ma Shao nodded. "To be specific, this detector uses an effect I call 'eddy current'. Of course, others may not fully understand this effect yet."

"Including Michael Faraday," he added.

Faraday was still alive at this time and was a scientist of great reputation.

"It sounds amazing." Rainy Day stroked his chin, "But this thing doesn't seem to have much practical significance. What do you plan to use it to detect, iron ore?"

Ma Shao: "It can't detect iron ore. In fact, it can't detect almost any ore. After all, it is a metal detector, not a metal mineral detector - except for gold mines."

"Why?"

Ma Shao continued to explain: "Because gold does not easily participate in chemical reactions, it often exists in the form of a single substance in nature."

Rainy Day thought for a moment and said, "So you're going to use it to look for gold?"

"Well... not really." Ma Shao thought for a moment, "After all, gold mines are always rare. North America is such a large place, how long will it take for this small detector to find gold mines?"

He was actually detecting gold mines.

Although the performance of this detector is not very good, it is definitely better than the naked eye.

The area being explored is not too large, just near Sacramento, so it should be relatively easy to find results.

But it is obviously inappropriate to say it directly now, after all, it is so early now... If he said there is a gold mine near Sacramento, it would inevitably give people a feeling of being appointed.

It would be stupid to use this thing to search for gold mines across the entire continent without specifying a smaller area.

"In that case, what's the use of this thing?" Rainy Day asked again.

"..." Ma Shao didn't know how to answer for a moment, and finally had to quote Faraday's famous saying, "What can a newborn baby do?"