Detcon DM-200 - Manual (Page 5)

Model DM-200
DM-200 Instruction Manual Rev. 2.0 Page 1 of 40
1. Introduction
1.1 Description
Detcon UniTox™ Model 200 Series universal toxic sensors are non-intrusive “Smart” sensors designed to
detect and monitor for toxic gases in the ppm range. The UniTox™ sensor family also includes ambient O
2
detection in the 0-25% range. UniTox™ sensors are designed to operate as standard two-wire 4-20 mA loop-
powered devices. Their intrinsically safe electronics design, when used with specified intrinsically safe field
wire barriers, conforms to a Class 1, Division 1, Group A, B, C, D area classification. The Sensor Assembly
includes a metal Nema 7 junction box and electropolished 316SS ISM assembly
The UniTox™ gas sensor consists of two major components: 1) the Universal Transmitter Module (UTM) and
2) the gas/range specific Intelligent Sensor Module (ISM). The universality of the design allows any ISM type
to be plugged into any UTM with seamless operation. The ISM consists of an electrochemical toxic gas
sensor and associated PCB providing pre-amplifier, microprocessor, and memory storage functions.
A 2-line 16-character alpha/numeric LCD is used to display sensor readings and provides the user interface
with the sensor’s menu driven features via a hand-held programming magnet.
Typical ranges of detection are 0-1ppm, 0-10ppm, 0-25ppm, 0-50 ppm, and 0-100ppm. Other ranges are
available and all ranges are covered by this manual. To determine model number, gas type, and range of
detection, reference the labeling on the ISM or refer to the instructions found in Section 10 (View Program
Status).
Figure 1 UniTox Sensor assembly
1.2 Sensor Technology
The sensors are electrolytic chemical cells. Each cell consists of three electrodes embedded in an electrolyte
solution, housed beneath a diffusion membrane. Sensitivity to specific target gases is achieved by varying
composition of any combination of the sensor components. Good specificity is achieved in each sensor type.
The cells are diffusion limited via small capillary barriers resulting in long service life of up to 3 or more
years. The oxygen cell is of the two-electrode, galvanic metal air battery type that functions as a direct current
generator proportional to the amount of oxygen adsorption.