Instruction Manual

748213-S April 2002

Model 755R

±15 V Power Supply Section

This section provides DC voltage required for various amplifiers and other circuits.

Fullwave rectifier bridge CR5 provides both positive and negative outputs. Each is routed through an associated series type integrated circuit, voltage regulator, providing regulated outputs of +15 V and -15 V.

Detector Temperature Control Section

This section maintains the detector at a controlled temperature of 150°F (66°C). Temperature is sensed by RT1, a resistance element permanently attached to the detector assembly. The signal from the sensor is applied to amplifier AR6, which drives transistors Q2 and Q3, thus controlling application of DC power from full wave rectifier bridge CR6 to two heaters within the detector/magnet assembly: HR1, mounted on the top of the magnet and HR2, permanently mounted on the rear of the detector assembly.

Detector Compartment Temperature Control Section

This section maintains the interior of the detector compartment at a controlled temperature of 140°F (60°C). Temperature is sensed by a thermistor located in the detector compartment and plugged into the Control Board assembly.

The circuit provides an on-off control of heater element HR3 via TRIAC element Q7. Heater HR3 is a part of the heater/fan assembly.

a.Isolated Current Output Board (Op- tional)

An isolated current output is obtainable by insertion of an optional plug-in circuit board into receptacle J1 on the Control Board (see Figure 3-1, page 3-3). The current outputs available by this board are 0 to 20 mA or 4 to 20 mA.

4-6 Theory

Rosemount Analytical Inc. A Division of Emerson Process Management