Teledyne T200, Руководство по эксплуатации, Страница: 318 / 425

Principles of Operation Teledyne API
– T200 NO/NO2/NOx Analyzer Operation Manual
316
Inp
ut
G
a
in Se
lec
to
r
1
–
11
Type
K
C
ompe
ns
a
tion
4
–
14
O
utpu
t S
ca
le Se
lec
tor
2
–
12
Te
rm
ina
tion
S
elec
tor
5
–
15
TC2
Not Used
TC1
Ty
pe
J Co
mpen
sa
tion
3
–
13
Purple Jumpers
Figure 13-17: Thermocouple Configuration Jumper (JP5) Pin-Outs
13.4. SENSOR MODULE
The T200 sensor assembly (Figure 12-9) consists of several subassemblies, each with
different tasks:

The Photo Multiplier Tube (PMT) detects the intensity of the light from the
chemiluminescence reaction between NO and O
3
in the reaction cell. It outputs a
current signal that varies in relationship with the amount of light in the reaction cell.

The PMT Preamplifier PCA converts the current output by the PMT into a voltage
and amplifies it to a signal strong enough to be usable by the motherboard’s A  D
converter. It also supplies the drive voltage and gain adjustment for the PMT’s High
Voltage Power Supply (HVPS)

The Thermo-Electric Cooler (TEC) controls the temperature of the PMT to ensure
the accuracy and stability of the measurements.
13.5. PHOTO MULTIPLIER TUBE (PMT)
The T200 uses a photo multiplier tube (Figure 12-9) to detect the amount of
chemiluminescence created in the Reaction Cell.
A typical PMT is a vacuum tube containing a variety of specially designed electrodes.
Photons from the reaction are filtered by an optical high-pass filter, enter the PMT and
strike a negatively charged photo cathode causing it to emit electrons. A high voltage
potential across these focusing electrodes directs the electrons toward an array of high
voltage dynodes.
The dynodes in this electron multiplier array are designed so that each stage multiplies
the number of emitted electrons by emitting multiple, new electrons. The greatly
increased number of electrons emitted from one end of electron multiplier are collected
by a positively charged anode at the other end, which creates a useable current signal.
This current signal is amplified by the preamplifier board and then reported to the
motherboard.
06858E DCN7057