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While catalytic LEL sensors often operate with little trouble in many application, the presence of silicon vapors, hydrogen sulfide and halogenated hydrocarbons can quickly degrade sensor operation. Measurement using an infrared sensor does not result in the combustion of the target gas, so the formation of acid gases or catalytic poisons does not occur on the sensor. This often means better zero stability and much longer sensor life with the IR system. In addition, calibration stability of IR sensors tends to be greatly improved, as the sensor is automatically compensated for changes in the IR source and detector that might cause calibration drift.
The D12-IR is also available with an infrared sensor designed for CO2 measurements in ambient air or in pumped gas samples. Two carbon dioxide sensors may be specified, one for low range use and another for higher levels of CO2. The low range sensor may be scaled from 0-1% minimum to 0-5% maximum, while the high range sensor covers ranges from 0-5% minimum to 0-50% maximum.
Features
- Explosion proof sensor design - Infrared sensing element is protected inside a stainless steel assembly with a sintered stainless steel flame arrestor.
- Fail safe sensor operation - Because the IR sensor is always in an active state, the transmitter continuously monitors critical sensor functions and indicates any sensor problems both on the display and through the analog output. Trouble can also be indicated by use of optional relays.
- High range methane measurement - D12-IR transmitters can be supplied calibrated for volumetric methane measurements for special applications. Ranges from 0-10% to 0-100% by volume are available.
- Three internal alarm relays - D12 transmitters contain relays that can be used for local alarm functions. All relays are programmable for setpoint, hysteresis, on-delay, off-delay and other variables.
- Serial communication interface - The transmitter is available with either HART or MODBUS protocol. The HART protocol supports the HART Universal and Common Practice
Commands at 1200 baud using the Bell 202 FSK modem standard. The MODBUS protocol supports 9600 baud access to concentration and status information and supports alarm setup and many other functions on either RS485 or RS232 (software selectable). Comes with a register/tag database on a 3 1/2" diskette.
- LCD graphics display - Gas concentrations are displayed in large, easy to read numbers. The display also provides alarm indication and complete menus for setting up operating parameters. A back light is available when operating in 3 wire mode.
- Internal data logger - Measured gas values are stored at user definable intervals and can be recalled when needed on the LCD display. Data can be downloaded using an ASCII interface to terminal or printer only.
- Sensor calibration history - Each time a sensor is zeroed or calibrated, the data is stored in memory. Calibration history can be recalled and sensor condition reviewed by operating personnel whenever necessary.
- Non-intrusive operation - Operating functions such as calibration, alarm setup, alarm rest, data view and setup options are all available using a magnetic tool. It is never necessary to open the enclosure when making adjustments.
- Password protection - Program setting stored in the transmitter may be protected by a user selectable password. Operators may still review all function, but changes may only be made by authorized personnel.
- Output simulation - Transmitter analog output can be set to user definable values and relay outputs can be set to specific states for complete simulation of detection system operation. Output and alarms may also be inhibited for maintenance and calibration.
- Modular transmitter electronics - The D12 electronic assembly plus easily into a terminal board in the base of the enclosure. Transmitters can be easily removed for wiring and quickly replaced in the event of a fault condition.
- Explosion proof enclosure - Transmitters are designed for operation in hazardous areas. The case aluminum housing for the D12 transmitter is rated for Class 1, Division 1, Groups B, C, D locations is UL, FM and CSA certified.
Specifications
| Sensor Type |
Single path infrared |
| Sensor Separation |
Maximum 25' cable from sensor to transmitter |
| Range |
Combustible Gas: 0-50% LEL min, 0-100% max
Volumetric Methane: 0-10% min, 0-100% max
Carbon Dioxide: 0-1% min, 0-50% max |
| Accuracy |
+/-5% of value, but limited by available calibration gas accuracy |
| Gases Available |
Combustible gas, carbon dioxide or volumetric methane. Combustible gas selectable for methane, propane or butane Consult factory for other gases and vapors. |
| Response Time |
T90 < 10 seconds |
| Electronic Repeatability |
+/- 1% |
| Electronic Linearity |
+/- 0.5% |
| Zero Drift |
Less than 1% of full scale per month, non cumulative |
| Span Drift |
Dependent on operating environment but generally less than 1% per month |
| Serial Interface |
Hart (1200 baud modem interface)
Modbus (1200-9600 - RS232 or RS485 s/w selectable) |
| Optional Alarm Relays |
Three SPST, 5 A @ 230 VAC resistive |
| Relay Coil |
programmable either normally energized or normally de energized |
| Analog Output |
Powered at 4-20mA, 675 ohms maximum at 24 VDC |
| Power |
12-30 VDC, 350 mA maximum (3W average) |
| Temperature Limits |
-40 to 75°C |
| Controls |
4 magnetic switches on front of transmitter |
| Enclosure |
Class 1 Div 1, Groups B, C & D |
| Weight |
4 pounds |
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