Detcon DM-634 - Manual (Page 5)

3.1 P RINCIPLE OF O PERATION
Method of detection is by a controlled rate of diffusion. Air and gas diffuse through a sintered stainless steel f ilter
and a diffusion barrier. As oxygen is adsorbed into the electrolyte solution a current is generated between the cath-
ode and anode electrodes. This current output rises with increases in oxygen concentration and reverses with lower
concentrations. The quick response of the cell results in continuous monitoring of ambient air conditions.
3.2 A PPLICATION
Model DM-634 MicroSafe™ sensors are designed to detect and monitor oxygen deficiency in ambient air in the range
of 0-25%. Minimum sensitivity and scale resolution is 0.1%. Operating temperature range is -4° F. to +122° F. While
the sensor is capable of operating outside these temperatures, performance specifications are verified within the limit.
3.2.1 Sensor Placement/Mounting
Sensor location should be reviewed by facility engineering and safety personnel. Area leak sources and perimeter
mounting are typically used to determine number and location of sensors. The sensors are generally located 2 - 4
feet above grade.
3.2.2 Interference Data
Methane 100% = 0
Hydrocarbons 100% = 0
Hydrogen 100% = < -2%
Carbon Monoxide 20% = < -0.5%
3.3 S PECIFICATIONS
Method of Detection
Air battery diffusion/adsorption
Electrical Classification
Class I; Groups B, C, D; Div. 1.
Response Time (T90)
T90 < 20 seconds
Clearing Time
90% < 20 seconds
Repeatability
± 2% FS
Range
0-25% O2
Operating Temperature
-4° to +122° F
Accuracy
± 2% FS
Sensor Warranty
2 year conditional
Detcon Model DM-634 Oxygen Sensor PG.5
Functional
Block
Diagram
Functional
Block
Diagram
Analog 4-20 mA Out
Power In
Relays Out
Pre-Amp Display
Temperature
Compensation
Alarm & Fault
Relays
RS-485 & 4-20mA
Micro-
processor
Transmitter
Power Supply
Sensor
Element
I/O Circuit
Protection
Serial RS-485 Out