THEORY OF OPERATION
6 - 2
The PID sensor for this UltraRAE monitor is constructed as a
small cavity in front of the UV lamp. A diaphragm pump is
installed inside the monitor enclosure to draw air sample into
the sensor through the gas separation tube and then exits
through the gas outlet port on the side of the enclosure.
A single chip microcomputer is used to control the operation of
the alarm buzzer, LED, pump and light sensor. It measures the
sensor readings and calculates the gas concentrations based on
calibration to known standard gases. The data is stored in non-
volatile memory so that it can be sent to a PC for record
keeping. RS-232 transceivers provide a serial interface between
the monitor and the serial port of a PC. An LCD display
consisting of a single row of eight alpha/numeric characters is
used to display the readings. The user interacts with the
monitor through three keys on the front panel keypad.
The monitor is powered by a rechargeable NiMH, NiCd battery,
or an alkaline pack.
NOTE: The printed circuit board of the monitor is
connected to the battery pack even if the power is
turned off. Therefore, it is very important to
disconnect the battery pack before servicing or
replacing any components inside the monitor.
Severe damage to the printed circuit board may
occur if the battery pack is not disconnected before
servicing the unit.
