GPR-1200 Portable ppm Oxygen Analyzer - Advanced Instruments Inc.

More documents

Recommendations

Info

ElectronicsThe signal generated by the sensor is processed by state of the art low power micro-processor based digital circuitry. The firststage amplifies the signal. The second stage eliminates the low frequency noise. The third stage employs a high frequency filterand compensates for signal output variations caused by ambient temperature changes. The result is a very stable signal.Sample oxygen is analyzed very accurately. Response time of 90% of full scale is less than 10 seconds (actual experience mayvary due to the integrity of sample line connections, dead volume and flow rate selected) on all ranges under ambientmonitoring conditions. Sensitivity is typically 0.5% of full scale low range. Oxygen readings may be recorded by an externaldevice via the 0-1V signal output jack.Power is supplied by an integral rechargeable lead acid battery which provides enough power to operate the analyzercontinuously for approximately 60 days. An LED located on the front panel provides a blinking 72 hour warning to recharge thebattery. A 9VAC adapter (positive pole located on the inside of the female connector) can be used to recharge the battery froma 110V or 220V convenience outlet. The analyzer is designed to be fully operational during the 8-10 hour charging cycle whichis indicated by a second continuously lit LED.Sample SystemThe GPR-1200 is supplied with a unique bypass sample system which enables the user to isolate the sensor from exposure tohigh oxygen concentration which results in a substantial increase is user productivity. However the sample must be properlypresented to the sensor to ensure an accurate measurement.For ppm trace oxygen measurements, the sensor is exposed to sample gas that must flow or be drawn through the analyzer’sinternal sample system. This unique sample system, when operated accordingly to the instructions in this Owner’s Manual, cansignificantly increase user productivity by minimizing the sensor’s exposure to ambient air or high oxygen concentrations whichcontribute to the significant amount of downtime associated with competitive analyzers.As illustrated above, the GPR-1200’s internal sample system includes:‣ 1/8” tube fittings for the inlet and outlet‣ flow control metering valve‣ 4-way sample/bypass valve to purge lines and isolate the sensor‣ Stainless steel sensor housing with an o-ring seal to prevent the leakage of air‣ Flow indicator common to bypass and sample linesUsers interested in adding their own sample conditioning system should consult the factory. Advanced Instruments Inc. offers afull line of sample handling, conditioning and expertise to meet your application requirements. Contact us at 909-392-6900 or e-mail us at info@aii1.com10
Accuracy & CalibrationSingle Point Calibration: As previously described thegalvanic oxygen sensor generates an electrical currentproportional to the oxygen concentration in the sample gas.Absolute Zero: In the absence of oxygen the sensor exhibitsan absolute zero, e.g. the sensor does not generate a currentoutput in the absence of oxygen. Given these linearity andabsolute zero properties, single point calibration is possible.Pressure: Because sensors are sensitive to the partialpressure of oxygen in the sample gas their output is afunction of the number of molecules of oxygen 'per unitvolume'. Readouts in percent are permissible only when thetotal pressure of the sample gas being analyzed remainsconstant. The pressure of the sample gas and that of thecalibration gas(es) must be the same (reality < 1-2 psi).Temperature: The rate oxygen molecules diffuse into the sensor is controlled by a Teflon membrane otherwise known as an'oxygen diffusion limiting barrier' and all diffusion processes are temperature sensitive, the fact the sensor's electrical outputwill vary with temperature is normal. This variation is relatively constant 2.5% per ºC.A temperature compensation circuit employing a thermistor offsets this effect with an accuracy of better than +5% (over theentire Operating Range of the analyzer) and generates an output function that is independent of temperature. There is no errorif the calibration and sampling are performed at the same temperature or if the measurement is made immediately aftercalibration. Lastly, small temperature variations of 10-15º produce < 1% error.Accuracy: In light of the above parameters, the overall accuracy of an analyzer is affected by two types of errors: 1) thoseproducing 'percent of reading errors', illustrated by Graph A below, such as +5% temperature compensation circuit, tolerancesof range resistors and the 'play' in the potentiometer used to make span adjustments and 2) those producing 'percent of fullscale errors', illustrated by Graph B, such as +1-2% linearity errors in readout devices, which are really minimal due to today'stechnology and the fact that other errors are 'spanned out' during calibration. Graph C illustrates these 'worse case'specifications that are typically used to develop an transmitter's overall accuracy statement of < 1% of full scale at constanttemperature or < 5% over the operating temperature range. QC testing is typically < 0.5% prior to shipment.Example: As illustrated by Graph A any error, play in the multi-turn span pot or the temperature compensation circuit, duringa span adjustment at 20.9% (air) of full scale range would be multiplied by a factor of 4.78 (100/20.9) if used formeasurements of 95-100% oxygen concentrations. Conversely, an error during a span adjustment at 100% of full scale range isreduced proportionately for measurements of lower oxygen concentrations.11
Page 2 and 3: Table of ContentsIntroduction 1Qual
Page 4 and 5: 3 General Safety & InstallationSafe
Page 6 and 7: drawn through metal tubing inside t
Page 8 and 9: 4 Specifications *Accuracy:Analysis
Page 12 and 13: Mounting the AnalyzerNormally mount
Page 14 and 15: Establishing Power to the Electroni
Page 16 and 17: For example, if the analyzer is rea
Page 18 and 19: MAIN MENUAUTO SAMPLEMANUAL SAMPLECA
Page 20 and 21: ‣ Always calibrate at the same te
Page 22 and 23: MAIN MENUAUTO SAMPLEMANUAL SAMPLECA
Page 24 and 25: 8. Remember steps #29-30 and #32-33
Page 26 and 27: and, the NPT end is taped and secur
Page 28 and 29: 7 Spare PartsRecommended spare part
Page 30 and 31: Symptom Possible Cause Recommended
Page 32 and 33: 10 MSDS - Material Safety Data Shee

GPR-1200 Portable ppm Oxygen Analyzer - Advanced Instruments Inc.

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?