Chapter 167: Grounding and Thresholds

At nine o’clock on Monday morning, the electronics market had just opened. Lin Chen dragged his suitcase along, his stride shortened by a full third from usual. Two layers of cardboard were stuffed around his left ankle, and his shoelaces were pulled as tight as they would go, but every step still felt like stepping onto waterlogged cotton. He walked into a shop specializing in industrial cables and asked for ten meters of four-square-millimeter yellow-and-green grounding wire, plus two packs of heat-shrink tubing and a set of insulated crimp terminals. The shop owner measured the cable diameter with a vernier caliper and quoted the unit price. Lin Chen scanned to pay and shoved the coil into the side pocket of his backpack. The shop smelled of rubber and oxidized copper. Standing at the counter while waiting for change, he lowered his head and rubbed his right calf. The muscle had already gone stiff; the soreness from compensating with it was creeping upward along his Achilles tendon.

When he got back to the dorm, he opened the shockproof case again. Last night’s test data had already been exported. In the log file, one line was highlighted in yellow:

[WARN] Weak signal at Node B. Retry 3 times. OK.

The handshake retry mechanism had worked under weak-network conditions, but the latency was still high. He opened the terminal, changed the heartbeat packet interval from five seconds to three, and added a rule to the local cache strategy: if two packets were dropped in a row, the system would automatically switch to offline mode, store the data temporarily on the TF card, and upload it in batches once the network recovered. After making the changes, he compiled and packaged everything. The progress bar reached one hundred percent. He pulled out the USB drive and stuck on a label:

Deployment_Package_v3.1_Offline

He checked the spare sealing strips, conformal coating, hex key set, and electrical tape once more, then stuffed them into the inner compartment of the toolbox. When he zipped it shut, it made a dull rasping sound.

At two in the afternoon, he turned in the dorm key. The counselor signed off in the duty office and did not ask questions. Lin Chen packed his laptop, USB drive, toolbox, and shockproof case into a somewhat worn hiking backpack and pulled the zipper all the way up. The weight pressed down on his shoulders with the center of gravity tilted to the right. He adjusted the straps and pushed open the door to go downstairs. In the stairwell, the motion-sensor lights flicked on floor by floor with the sound of his footsteps, then went out behind him floor by floor.

The long-distance bus left at four in the afternoon. The cabin was thick with the mingled smell of instant noodles, leather, and sweat. Lin Chen chose the window seat in the last row and held his backpack in his arms. As the wheels rolled over the national highway, every bump traveled through the seat into his spine. He closed his eyes and silently recited the workshop wiring diagram from memory: Phase A incoming line to terminal strip 1–3, Phase B to 4–6, grounding wire crimped with a copper lug and fastened to the bottom plate of the cabinet. Beneath the seat, his left foot gradually went numb. Now and then, he pressed his right thumb into his calf to ease the muscle stiffness. Outside the window stretched endless factory buildings and cooling towers, their gray-white outer walls fading into dark blue in the dusk. The outline of the industrial zone grew clearer and clearer, and the air began to carry the smell of metalworking fluid and engine oil. The bus turned onto a side road, and a speed bump sent a stabbing pain through his left ankle. He clenched his teeth and made no sound.

At 7:20 that evening, the bus stopped at a temporary drop-off point outside the factory grounds. Lin Chen got off and staggered when his left foot hit the ground. He caught himself against a lamppost, steadied himself, and drew in a deep breath of cold air laced with dust. Dragging his case, he headed for the south gate. The incandescent bulb in the guard booth was on, and an old man in uniform leaned his head out.

“Who are you looking for?”

“Phase Two line debugging. Professor Zhou referred me. I’m here for Director Wu.” Lin Chen handed over his ID card and letter of introduction.

The old man checked the register, then picked up the walkie-talkie and called out twice. Five minutes later, a man in dark blue coveralls with graying temples came over at a brisk pace. He was not tall, but his shoulders were broad, and he had a ring of keys and an access card in one hand.

“Lin Chen?”

“Yes.”

“Come with me. Hand over your phone. No electronic devices are allowed in the workshop. Put your hard hat on and change into safety shoes.” Director Wu spoke quickly, with no small talk. He pointed to the sheet-metal locker beside them. “You can bring your case, but once you’re inside, it can only stay at the designated station. You’ve got a four-hour window. Miss it and that’s it. The night shift doesn’t stop the line. If you connect even one wire wrong, the whole line has to shut down.”

Lin Chen did as instructed. He locked his phone in the cabinet and changed into heavy steel-toe safety shoes. The uppers were stiff, and his left foot hurt badly from the pressure, but he said nothing. Director Wu swiped the card and opened the door. The heavy iron door swung inward, and a wave of heat mixed with metallic dust hit him in the face. The exhaust fans overhead in the workshop droned loudly, but they could not overpower the thunder of dozens of punch presses and CNC machines below. The light was the ghastly white of fluorescent tubes, shining down on oil-stained concrete. The air felt dense; when he breathed, he could feel fine particles scraping at his throat.

“Node A is beside Machine No. 7. Node B is behind the power distribution cabinet.” Director Wu pointed deeper inside. “The cable trough has already been reserved, and the ground bar is over there. Do the wiring yourself. Once you’re done, power it on and run the script. If there’s a problem, call me. If there isn’t, keep quiet.”

“Understood.”

Lin Chen dragged his case over to Machine No. 7. The cabinet was empty, and the internal cable troughs were coated in dust. He put on a dust mask and protective goggles and knelt on the floor. His right knee touched down; his left leg, unable to bend, could only stay stretched out and suspended. He opened the toolbox and laid out the wire stripper, crimping pliers, and screwdrivers in a neat row.

First came the grounding wire. He stripped off the insulation, exposing the copper core, slipped on the copper lug, and compressed it tight with the hydraulic crimper. The feel was solid; the crisp bite of metal into metal was almost inaudible in the noise. He fastened one end of the grounding wire to the cabinet’s ground bar on the bottom plate and routed the other to the wall’s main grounding grid. After tightening the screw, he tugged it by hand. It did not budge.

Then came the signal wires. Four shielded cables ran through the trough and into the terminal strip. Following the drawing, he crimped them one by one into the corresponding positions. The edge of the metal sliced a cut into one of his fingers, and a bead of blood welled out. He pressed it with a tissue and kept tightening screws. Sweat ran down from his forehead into his eyes, stinging sharply. He blinked once and did not stop. His left foot had already lost all sensation, hanging from him like a dead piece of wood. He could only maintain the posture by relying on his core and his right leg, and every screw he tightened made the muscles in that leg twitch once. Dust settled over the antistatic mat, quickly building into a thin layer. He wiped the sweat off his forehead with the back of his hand and kept stripping, crimping, and fastening. The motions were mechanical, but the rhythm never faltered.

By 8:40, the wiring was finished. He took out the terminal device and plugged in the USB drive. The screen lit up. He entered the command and began the offline deployment. The progress bar crawled upward:

Installing dependencies... 45%... 78%...

The workshop was too loud for him to hear the cooling fan, so he could only stare at the screen. At 9:10, deployment was complete. He removed the USB drive, closed the terminal device, and pressed the power switch on the side of the cabinet.

Click.

The relay engaged. Indicator lights on the board lit one after another: green, green, yellow, green. The cooling fan began to turn, though its sound was swallowed whole by the workshop’s roar. He opened the log monitoring window, and data began scrolling:

[INFO] System boot. CPU: 41°C. Memory: 12%. [INFO] Sensor A connected. Vibration: 0.8mm/s. [INFO] Sensor B connected. Temp: 38°C. [INFO] Heartbeat: 3s. Local cache: active.

He leaned against the cabinet and let out a long breath. The cramping in his right leg had already spread into his thigh, and he reached down to knead it hard. By 9:45, the data had stabilized. He walked to Node B behind the power distribution cabinet and repeated the inspection. The sealing strip fit well, there was no dust adhering to the surface of the conformal coating, and the temperature was sixty-two degrees—within threshold.

At 10:30, Director Wu came over and glanced at the logs on the screen.

“It runs?”

“It runs. The vibration threshold is set to 2.5, temperature alarm at 70. Offline cache is already enabled,” Lin Chen replied.

Director Wu nodded without speaking. He reached out to touch the cabinet housing, then looked at the grounding wire. “Grounding job’s decent enough. Tomorrow, when the day shift starts the line, keep an eye on it. If the script crashes, that’s on you. The factory pays by piecework. One minute of downtime costs two hundred.”

“Understood.”

Director Wu turned and left. Lin Chen packed up the toolbox and moved the shockproof case into the corridor outside the workshop. Leaning against the wall, he took off the safety shoe. His left ankle had already swollen all the way around, the skin flushed red. He dug out a spray can of Yunnan Baiyao from his bag and sprayed it twice. The cold bit into him to the bone. He closed his eyes and listened to the roar of the workshop machines starting up again. The night shift had begun.

At 11:20, he opened the terminal device again. The log window was still scrolling. Then suddenly, a yellow line popped up:

[WARN] Node A vibration spike: 2.1mm/s. Duration: 4s. Threshold not reached.

Lin Chen opened his eyes. The vibration peak was close to the threshold, but it lasted only a short time. He pulled up the historical curve and found that the peak had occurred at the instant the punch press changed dies. It was not an equipment fault, but a transient impact caused by a process switch. His fingers tapped a few times on the keyboard, and he added a filtering rule to the script: only trigger a warning if three consecutive samples exceeded 2.0; ignore a single isolated spike. Save. Hot update. The logs returned to steady calm.

He leaned against the wall, the screen’s cold glow reflected on his face. A window at the far end of the corridor stood open, and the night wind poured in, blowing away the smell of engine oil. His phone was in the locker, out of reach. But he knew that when the day shift started the line tomorrow morning, the real test would begin. Could the script withstand eight straight hours of heavy load? Under Director Wu’s rules, even one minute of downtime would cost performance pay. He closed the terminal device and tucked the spray back into his bag. His left foot was still numb, but his breathing was steady.

The motion-sensor light in the corridor went out. In the darkness, only the breathing light on the terminal device screen blinked faintly. He took out his notebook, turned to a fresh page, and wrote:

23:45 Punch press die change transient impact triggered false alarm. Sliding-window filter added. Must record actual load curve during tomorrow’s day shift. Recheck grounding resistance.

The pen paused for a moment. He remembered what Old Zhao had said last time:

“What matters to the factory isn’t whether they approve it. It’s whether you can keep the line from stopping.”

He closed the notebook. When the sun rose tomorrow, the board would have to start breathing for real. And in the workshop, the night shift was only halfway through.