I started with a ship full of max-level veterans, and I'm just a complete noob.

"First, get the furnace temperature accurate, then we can discuss how to heat it."

Jiang Ming pressed his finger on the recording paper, moving it to the right along the undulating curve, and placed it on the highest peak.

Wu Hanzhang stood beside the germanium ingot sample box, scanning it with his probe: "The temperature measurement is inaccurate, how do we modify the furnace?"

"Therefore, temperature measurement, comparison, and voltage regulation should be integrated into the same closed-loop circuit."

Huang Kun's chalk was still covered in white dust. Upon hearing this, he quickly turned back to the edge of the table and placed another sheet of record paper on top of it.

The curves on the paper generally undulate along the same baseline. When the melting zone passes through the middle section of the germanium rod, the peaks rise one after another, and the fall process is very long. Several fluctuations cross three degrees Celsius.

"This batch uses carbon rod furnaces. The previous batch used silicon carbide rods, and we also tried molybdenum wire, but the results were about the same."

Huang Kun held the chalk between his fingers and pointed to the three lines of numbers on the blackboard.

"The width of the melting zone is eight to twelve millimeters, the germanium rod is advanced at a speed of one to three millimeters per minute, and the temperature must be kept at around 937 degrees Celsius, with an allowable error of plus or minus one degree Celsius."

He drew two lines under the last number.

"The first two issues can be resolved with mechanisms and coils, but the third is a fatal flaw."

From the other side of the workbench came the sound of metal clamps clattering. Lin Lanying was taking a quartz boat out of the fume hood. The bottom of the boat was covered with a layer of grayish-white crystals, and the edges still had fine lines left from the last melting.

"We tried three different heating elements: carbon rods were slow to heat up, silicon carbide rods heated up too quickly, and molybdenum wires had a narrow and unstable heating zone."

She placed the quartz boat back on the tray, wiped the powder off her gloves, and then looked at Jiang Ming.

"Comrade Jiang, your Third Electronics Factory makes magnetrons. The temperature control of vacuum exhaust and cathode firing is separated from regional purification by a process layer."

This statement is polite, but it clearly establishes a distance between them.

"What we need here is a temperature gradient of plus or minus 0.1 degrees Celsius, not to maintain the furnace temperature within a general range."

"you're right."

Jiang Ming folded the record sheet back to its original position.

"You're currently using constant current heating, and we manually monitor the pyrometer and adjust the transformer."

Lin Lanying paused the tweezers in her hand above the quartz boat, then put them back next to the vessel.

"The pyrometer readings can be seen, and manual adjustments can keep up; for now, this is the only open-loop solution."

"It can keep up with temperature changes, but not with changes in the melting zone."

Jiang Ming pointed to the peak of the curve.

"The front edge of the melting zone is affected by heating, while the rear edge is affected by crystallization and heat dissipation. The temperature changes on both sides are in different directions. Single-point temperature measurement can only show one side. When the operator makes adjustments, the other side has already gone through the compensation time."

Huang Kun glanced at him, turned around, picked up the chalk, and wrote two words in the lower right corner of the blackboard.

"closed loop."

"right."

Jiang Ming stopped talking and simply placed a pencil horizontally between the curve and the blackboard.

"A temperature sensor is placed at the front and the rear edge, and the difference between the two is sent to the amplifier. The power regulator only processes the difference, and the common changes caused by the overall heating or cooling of the furnace body will be partially canceled out."

Upon hearing this, Lin Lanying casually picked up an old record and flipped it over.

"If both thermocouples are placed outside the quartz tube, can the readings represent the melting zone?"

"It can't be directly represented; calibration is needed."

"Thermocouples in the high-temperature range can drift."

"Therefore, we cannot only look at the absolute value of the thermocouple."

Jiang Ming took a steel ruler from the table and pressed it down on the corner of the recording paper.

"First, calibrate the two sensors using known temperature points, then send the differential signal between the two into the DC amplification stage. The control loop tracks the temperature difference before and after the melting zone, while the absolute temperature is corrected by the calibration curve."

Huang Kun put down the chalk and pressed his palm against the edge of the blackboard.

"You're talking about a compensation structure. The problem is that the signal changes little at high temperatures, and the amplifier's zero drift will swallow up the differential components."

"A vacuum tube amplifier can solve part of the problem."

Wu Hanzhang took over the conversation, his tone already showing a protective attitude.

"502 has been tested for high-temperature exhaust and weak current measurement. We can arrange for someone to test zero drift, shielding, and power supply stability."

Huang Kun pondered for a moment, then took out a yellowed photocopy of a paper from the table. The cover bore the name of Pufaen and the title of the regional purification.

"The principle is public, but the engineering implementation is all in each company's furnace."

He turned to the middle page and tapped a formula with his pencil.

"In theory, as the narrow melting zone moves along the material, impurities concentrate at one end according to the solid-liquid segregation difference, and repeating this several times can improve the purity."

Lin Lanying continued, "But when the temperature fluctuates, the segregation coefficient also changes, and the purity curve on the record loses its reference."

Huang Kun put the papers together.

"Old Wu, temperature control is only one part of the whole furnace. Quartz tube sealing, atmosphere protection, and precision of the propulsion mechanism all need to be matched."

He looked at Jiang Ming, his tone still gentle.

"If 502 is willing to make a temperature control component first, we welcome it. If you want to take on the whole system design, you must first prove your understanding of semiconductor materials and be able to cross the level of positive and negative three degrees."

Wu Hanzhang reached into his canvas briefcase, pulled out a crumpled empty cigarette box, and pressed his thumb back and forth along the edge of the box.

"Old Huang, since he dared to ask, let him try."

Why should I stop him?

Huang Kun smiled.

"The germanium material in the laboratory is precious, and the experimental procedures must be followed according to regulations. First, we use the temperature control unit for verification. Once the data passes the test, we then connect the quartz tube and the propulsion mechanism."

Jiang Ming pushed the photocopy of the paper back onto the table.

"Give me a proposal for a temperature control system in three days."

Lin Lanying looked at him with caution.

"Will the precision mentioned in the proposal be reflected in the actual product?"

"Look at the loop first, then look at the actual object."

Jiang Ming carefully put away the record sheet.

"As long as it is done in a closed loop, the issue of zero point plus or minus one degree is not the heating element's desire, but rather a matter of measurement and adjustment methods."

On the way back to the Third Electronics Factory, the jeep drove east along the western road of the city. The wheels rolled over a section of puddle, and Wu Hanzhang placed the empty cigarette box on his lap.

"You just made a promise."

"The temperature control solution can achieve this."

What guarantees do you have?

Jiang Ming looked out the car window and saw water accumulating on the roadside utility poles, flowing down the wooden posts.

"Use the proposal from three days later as a guarantee, and let it go through internally in 502 first. If it doesn't pass, just leave it in the drawer."

Wu Hanzhang squeezed the cigarette box, and the cardboard box made a soft sound.

"Three days. 502 internal testing is required first. If it doesn't pass, don't send it out."

By the time the car entered the Third Electronics Factory, it was already dark. The gatekeeper checked their credentials and let them into the technical area.

Jiang Ming handed the canvas bag to Comrade Song for registration, then went into room 502 alone. He first checked the door lock and window latches, then placed Qian Xuesen's black lecture notes, the temperature curves brought back from the Institute of Physics, and the catalog of Lei Zhenbang's posthumous manuscripts on the worktable.

The flame of the kerosene lamp flickered against the glass cover. Jiang Ming opened the lecture notes; the chapter on automatic control contained only half a page of content. Transfer functions, feedback, and stability were compressed into a few lines of text by Qian Xuesen in extremely simple handwriting.

He placed the pen on the paper and closed his eyes.

As his consciousness sank into the bronze pages of the book, the icon of the third fellow disciple lit up. Just as the page was about to turn to the section on precision instruments, a thin line suddenly extended from the side of the icon, passed through several layers of dark book veins, and stopped in front of a human-shaped silhouette.

Before the outline of the face could be fully revealed, several lines of dark text had already appeared beside it.

Director of the Precision Calorimeter Laboratory at the Technical University of Berlin, died in 1937.

Jiang Ming opened his eyes just as the flame of the kerosene lamp retracted into the wick.

He opened the manila notepad, left a blank space next to the name of his third classmate, and wrote down the name of the Technical University of Berlin and the Precision Calorimeter Laboratory.

This new path leads to the answer he desperately needs.