Analytical Industries GPR-2500 A Oxygen Analyzer - Manual (Page 26)

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Span Calibration
Maximum drift from calibration temperature is approximately 0.11% of reading per °C. The transmitter has been
calibrated at the factory. However, in order to obtain reliable data, the transmitter must be calibrated at the initial
start-up and periodically thereafter. The maximum calibration interval recommended is approximately 3 months, or
as determined by the user’s application.
Calibration involves adjusting the transmitter electronics to the sensor’s signal output at a given oxygen standard,
e.g. a certified span gas with an oxygen content (balance nitrogen) approximating 80% of the next higher full scale
range above the intended measuring range is recommended for optimum accuracy, see Calibration and Accuracy.
Calibration with ambient or instrument air (20.9% or 209,000 ) is recommended when installing a new sensor or
when a certified gas is not available.
Factory Default Span
The software will set the SPAN adjustment based on the average oxygen reading (actually the sensor’s signal
output) at a specified oxygen concentration. For example, when a span gas is introduced, the micro-processor will
display an oxygen reading within +50% of the span gas value. This feature allows the user to test the sensor’s
signal output without removing it from the sensor housing.
1. Access the MAIN MENU by pressing the MENU key.
2. Advance the reverse shade cursor using the ARROW keys to highlight MANUAL SAMPLE.
3. Press the ENTER key to select the highlighted menu option.
4. The following displays appears:
MAIN MENU
AUTO SAMPLE
MANUAL SAMPLE
CALIBRATE
24.5 C 100 KPA
>>>
CALIBRATION
SPAN CALIBRATE
ZERO CALIBRATE
DEFAULT SPAN
DEFAULT ZERO
24.5 C 100 KPA
Manual Span
The user must ascertain that the oxygen reading (actually the sensor’s signal output) has reached a stable value
within the limits entered below before entering the span adjustment. Failure to do so will result in an error.
Entering the span value – follow the menu layout in Appendix A.
Preparation - Required components: Refer to Installing Span Gas section above.
1. Certified span gas cylinder with an oxygen concentration, balance nitrogen, approximating 80% of the full scale
range above the intended measuring range.
2. Regulator to reduce pressure to between 5 and 30 psig.
3. Flow meter to set the flow between 1-5 SCFH,
4. 2 lengths of 1/8” dia. metal tubing measuring 4-6 ft. in length.
5. Suitable fittings and 1/8” dia. metal tubing to connect the regulator to the flow meter inlet
6. Suitable fitting and 1/8” dia. metal tubing to connect to the flow meter vent