Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 16)

Chapter 2 Model 402 R-EU
Teledyne Analytical Instruments 2-4
the side panel next to but outside of the isothermal chamber. See Figure
2-1. and consists of an electrometer amplifier and an operational amplifier.
This circuit is a very high-gain, current-to-voltage converter circuit, having
an input impedance measuring in the billions of ohms. It is static sensitive
and highly susceptible to contamination. Special care must be taken in
handling this PC board.
Refer to Section 5-4: Electrometer-Amplifier PC Board for more
information concerning the electrometer-amplifier and the other printed
circuits that follow.
2.1.3 Differential Power Supply
The positive and negative operating voltage required by the electrom-
eter-amplifier is furnished by a regulated, differential power supply circuit.
The output of the power supply as referenced to chassis ground is positive
15 (±1) VDC, and negative 15 (±1) VDC. Regulation is better than 1% of
the rated voltage.
2.1.4 Anode Power Supply
The high voltage anode power supply components are mounted on the
anode power supply printed circuit board. High voltage regulation is
achieved through the use of series-connected zener diodes. The simplicity
of this circuit’s design can be attributed to the extremely low current
demand of the anode circuit. The positive output voltage is nominally 250
volts. Output tolerance is ±22 volts from the specified 250 volts.
2.1.5 Flame Guard Circuit
A thermistor-controlled, transistorized switching circuit is employed
to operate a relay in the event of a flameout condition. A panel indicator
light and fuel shut-off solenoid valve are operated by the relay to alarm
personnel that a flameout condition has occurred. The fuel shut-off sole-
noid valve stops the hydrogen flow.
2.1.6 Flame Ignition Circuit
The flame ignition circuit includes the anode-igniter electrode (in the
detector cell), a transformer, and the momentary IGNITE position of the
selector switch.
2.1.7 Proportional Temperature Control Circuit
The temperature of the isothermal chamber containing the sampling
components is regulated by a thermistor-directed electronic circuit. The
thermistor and heating element are located in the chamber, and the balance
of the circuit components are mounted on the temperature controller
printed circuit board. A temperature limit switch protects the isothermal