Oxigraf, Inc.238 East Caribbean Drive
Sunnyvale, CA 94089
Phone:650.237.0155 • Fax:650.237.0159
E-Mail: sales@oxigraf.com • Web site: www.oxigraf.com
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07-0194 O2iL Oxygen Process Analyzer |
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07-0272 O2iC Oxygen Process Analyzer |
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Fast Response
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Modern process control requires fast response without overshoot. The Oxigraf Process Controller responds in less than a second. The transit time of the gas sample through the sampling tube may be 1 second per meter of sampling tube. To respond within 5 seconds, a monitor with a 1 second response time would need to be placed within 4 meters of the potential hazard. Electrochemical sensors may incorporate long averaging times, 20 or more seconds, for large, abrupt changes in oxygen concentration. Laser diode technology offers short response times to meet your control requirements. |
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Sample Flow Monitor
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The Oxigraf O2iL includes a sampling pump, hydrophobic filter, and flow sensor. The microprocessor controller maintains the flow at a constant value. Any flow blockage or pump failure is reported as a low flow fault. Filter impedance can also be measured to indicate a need for filter maintenance. Thus remote monitoring of the flow system is enabled. Pumps are available to provide sampling at atmospheres down to 200 Torr. |
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Temperature, Pressure and Humidity
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An error budget must be established for oxygen process control. Humidity changes can cause a large variation in the oxygen measurement. A hot, wet day relative humidity of 50% at 37ºC (99ºF) corresponds to an absolute humidity of 3.2%. Such a water vapor dilution would cause a variation from the cold, dry air oxygen concentration of 20.9 to 20.2%, a change of 0.7%. If 19.5% is to be the alarm value, then variations from all other sources must be substantially less than 0.7% (the difference between 19.5 and 20.2%). Therefore, temperature and pressure corrections are important. An oxygen sensor which measures oxygen partial pressure instead of concentration would report an oxygen variation of 2% with a 10% variation in barometric pressure. The Oxigraf sensor is corrected to within ±0.2% over pressure changes of 50% and temperature changes from 0 to 50ºC. |
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Remote Display
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The Oxigraf Process Controller includes various communication outputs of oxygen concentration, alarms, flow, and system status. It is essential for cost effective process control to have both local and remote indication of process control operation. Another advantage of a remote display we call “remote maintenance”. A major cost of oxygen process controllers is the requirement for periodic maintenance and recalibration. With remote maintenance, site service and recalibration are no longer required to be periodic. Any system, power, flow or measurement faults will be flagged on a remote display, and service and calibration can be performed on an as-needed basis. For example, choosing an average oxygen concentration in humid air of 20.7%, the central monitor might flag measurements outside a range from 20.2 to 21.2% as requiring a calibration visit; with such a remote maintenance protocol, a periodic calibration frequency might be annual or less frequent. |
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Tunable Diode Laser Spectroscopy
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The Oxigraf O2iL is the next generation oxygen process controller. Laser diode absorption spectroscopy assures stable, long-life oxygen measurement: there are no electrochemical cells to replace or paramagnetic sensors to recalibrate. The laser diode, derived from high reliability telecommunications VCSEL (vertical cavity surface emitting laser) diode technology, is rated for more than 100,000 hours mean time to failure. The laser diode is thermally and electronically tuned to measure the absorption of oxygen at 763 nm, and also periodically measures the background to provide an automated zero. Pressure and temperature corrections are made to yield the correct oxygen concentration as the weather changes. |
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Insensitivity to Movement
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The Oxigraf technology has no moving parts, in contrast to paramagnetic technology. Laser diode technology will have no false alarms due to equipment vibration, mechanical accidents, or even earthquakes. |
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Code Access
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Control of the unit via the 12-key capacitive-touch panel can be restricted by use of a password. This permits access control for maintenance and unit calibration. |
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Measurement Range
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2-100% (O-100% optional) |
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Accuracy
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±0.2% |
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Cross Sensitivity
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0.2% oxygen/nitrogen mixtures |
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Response Time
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500 ms at 200 ml/min flow rate, additional low pass filtering programmable. |
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Gas Inlet Temperature
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-20 to 60 ºC |
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Gas Pressure
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200 to 1150 Mb |
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Humidity
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0 to 95%, non-condensing |
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Warm-up Time
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5 minutes |
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Display Resolution
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0.01% O2 |
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Analog Output
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4 to 20 mA (max 750 ohm load), range programmable |
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Serial Outputs
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RS232 (TXD, RXD, Ground), RS485 Modbus compatible |
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Relays
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SPDT, 5 Amps, 115 VAC or 24 VDC Terminal strip |
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Limit Relay 1
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Programmable low limit or high limit, failsafe on/off |
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Limit Relay 2
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Programmable low limit or high limit, failsafe on/off |
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Low Flow Relay
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Active if sample flow problem |
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System OK Relay
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Programmable failsafe on/off |
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Power
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15 to 32 VDC, 1.5 A max, 0.6 A typical Terminal strip |
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Display
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16 x 2 character VFD, 8 mm character size |
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Optional Strobe
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Red lens flashing strobe |
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Optional Horn
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100 dB |
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Outside Dimensions
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300 x 250 x 165 mm |
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Conduit connection
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3/4 EMT x2 (supplied by the customer) |
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4-20 mA Connection
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Terminal strip |
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RS232 Serial
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Terminal strip and connector (Switchcraft EN3P3F) |
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RS485 Modbus Connection
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Terminal strip |
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Pneumatic Interface
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Diaphragm pump to 250 ml/min at 1010 mbar. Optional vane pump for use down to 100 mbar. PTFE inlet filter blocks condensate: any condensate must gravity drain down to the source. |
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Altitude Change
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If the altitude of operation of the sensor changes by more than 2000', two-point recalibration is required. |
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Enclosure
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Field Replaceable, unbolts with four screws. Electrical connections to a terminal board. Pneumatic connections slipfit or o-ring quick connects. NEMA 4X rated non-metallic box with Lexan window, wall mounted. Class 1, Division II purged optional |
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Auto-Calibration
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Auto Calibration is now standard for the absolute highest accuracy and the ultimate in ease of maintenance of your Oxigraf oxygen deficiency monitor. Connect to a cylinder of calibration gas or run tubing to a space where ambient air is known. Set the calibration interval to your specifications, and you will never need to worry about routine calibration maintenance. One point calibration is standard and two (2) point auto calibration is available as an option. |
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