Disk On Chip; Flash Chip; Sensor Module, Reaction Cell & Pmt; Reaction Cell Heating Circuit - Teledyne 200E Instruction Manual

Model 200E Instruction Manual Theory of Operation
the chassis on its own mounting bracket) to control the function of heaters and valves. The
CPU includes two types of non-volatile data storage, one disk-on-chip and one or two flash
chips.

10.3.1.1. Disk On Chip

Technically, the disk-on-chip is an EEPROM, but appears to the CPU as, behaves as, and
performs the same functions in the system as an 8 mb disk drive, internally labeled as DOS
drive C:\. It is used to store the computer's operating system files, the T-API firmware and
peripheral files, and the operational data generated by the analyzer's internal data
acquisition system (iDAS - Sections 10.4.5 and 6.11).

10.3.1.2. Flash Chip

The flash chip is another, smaller EEPROM with about 64 kb of space, internally labeled as
DOS drive B:\. The M200E CPU board can accommodate up to two EEPROM flash chips. The
M200E standard configuration is one chip with 64 kb of storage capacity, which is used to
store the analyzer configuration as created during final checkout at the factory. Separating
these data onto a less frequently accessed chip significantly decreases the chance of data
corruption through drive failure.
In the unlikely event that the flash chip should fail, the analyzer will continue to operate
with just the DOC. However, all configuration information will be lost, requiring the unit to
be recalibrated.
10.3.2. Sensor Module, Reaction Cell & PMT
Electronically, the M200E sensor assembly (Figure 10-13) consists of several subassemblies
with different tasks: to detect the intensity of the light from the chemiluminescence reaction
between NO and O in the reaction cell, to produce a current signal proportional to the
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intensity of the chemiluminescence, to control the temperature of the PMT to ensure the
accuracy and stability of the measurements and to drive the high voltage power supply that
is needed for the PMT. The individual functions are described individually below, Section
11.6.6 shows the sensor assembly and its components.

10.3.2.1. Reaction Cell Heating Circuit

The stability of the chemiluminescence reaction between NO and O can be affected by
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changes in the temperature and pressure of the O and sample gases in the reaction cell. In
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order to reduce temperature effects, the reaction cell is maintained at a constant 50° C, just
above the high end of the instrument's operation temperature range.
Two AC heaters, one embedded into the bottom of the reaction cell, the other embedded
directly above the chamber's exhaust fitting, provide the heat source. These heaters
operate off of the instrument's main AC power and are controlled by the CPU through a
power relay on the relay board (Section 10.3.4). A thermistor, also embedded in the bottom
of the reaction cell, reports the cell's temperature to the CPU through the thermistor
interface circuitry of the motherboard (Section 10.3.5).
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