This oxygen detector is produced by RKI of Japan, model number 0X-01. Judging from the date in the manual, it should be a product before 2004. It can be found on Taobao now, and the price is around 3K.
This type of detector is generally expensive. A single sensor costs 800 yuan. I also have a RAE five-in-one gas detector, which costs more than 10,000 yuan and is said to be only at the entry level. I will post a disassembly of it later.
This detector is designed to be very compact, with rubber covers on the top and bottom.
At the bottom is its battery compartment, which uses 2 AAA batteries for power.
There is a buzzer, LED light and replaceable oxygen sensor on the top. To replace the sensor, just remove the middle screw.
Open the top cover and you can see the oxygen sensor on the right and the buzzer on the left.
The sensor model is OS-BM2, which looks like a button battery.
By removing the top rubber strip, you can take off the entire circuit. There are three PCBs inside: a sub-board for connecting the sensor with no components on it, a bottom board for connecting the battery electrodes with a small number of components on it, and a main control board with a display screen. The main components are concentrated on the top.
There are not many devices on the large PCB. There is a chip with silkscreen LTFF near the board-to-board connector. It is the LT1494 from Linear Technology (acquired by ADI), a single/dual/quad channel Over-The-Top precision rail-to-rail input and output operational amplifier with a maximum of 1.5A.
LT1494.pdf
(258.95 KB, downloads: 3)
After unscrewing the screws, you can remove the small board with the display screen. There is also a vibration motor placed in the interlayer.
When you take a picture of the display, you can see a main control chip with a sticker on it.
After removing the sticker, I saw that it was a TI MSP430 microcontroller, model msp430p325,
msp430p325.pdf
(582.36 KB, downloads: 1)
.
The battery electrodes, internal circuits and sensors are all severely corroded.
There is a ferroelectric memory on the main control board, model FM24CL16B,
FM24CL16B.pdf
(484.55 KB, downloads: 1)
, a 16-Kbit (2K × 8) Serial (I2C) F-RAM from Cypress (now acquired by Infineon).
There is a SOT32-5 chip with JQMT silkscreen on the board, but the specific model is not found.
There is a chip in a SOT32-3 package with the silkscreen FZGI, which may be the MAX6006 from MAXIM-IC (acquired by ADI),
MAX6006–.pdf
(1.17 MB, downloads: 2)
, a voltage reference.
The oxygen sensor is difficult to remove and requires cutting off the metal wrapping around it.
The disassembly process can be seen in the video below:
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