RKI Instruments GX-94 - Manual (Page 13)

GX-94 Operator’s Manual Page 12
labels. The toxic sensor is housed in a cylindrical plastic shell with four
connection pins at the base for easy replacement. The membrane cov-
ered diffusion opening at the top of the shell allows atmosphere to dif-
fuse into the sensor.
The toxic sensors are electrochemical cells, which react to gas in the
atmosphere, producing a current proportional to the concentration of
gas. The current is converted by the GX-94’s circuitry into a measure-
ment of gas concentration.
Circuit Boards
The GX-94 circuit boards analyze, record, control, store, and display the
information collected. These circuit boards contain no user-serviceable
components.
A 3 volt coin type lithium data backup battery is located on one of these
circuit boards, the main CPU board, in a coin type battery holder. This
battery assures that any stored data and unit setup are not lost when
the main batteries are dead or are removed for replacement. The data
backup battery typically lasts for five years. See the Maintenance sec-
tion for instructions on replacing the data backup battery.