Frequently Asked Questions
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- Can we use nitrogen (in other words, 0% O2) to calibrate our Oxigraf X2004 sensor at the low calibration point?
- What is the span calibration cycle? Could you give me some explanations about span calibration?
- Would it be possible to have the X2004 loaded with a right-angled interface connector along the lines of Molex 70247 which is rated at 3A?
- What is the noise requirement of the power supply?
- What about communication with the X2004, do you have any sample code to get us started?
- Do you have any suggestions as to correct grounding for the X2004?
- What about connecting to the analog outputs for the X2004?
Q) Can we use nitrogen (in other words, 0% O2) to calibrate our Oxigraf X2004 sensor at the low calibration point?
A) You must calibrate the X2000 series with a gas mixture that contains at least 2% O2. Some absorption is necessary in order for the sensor line lock servo to maintain lock. The X2008 in high resolution, low range mode (0-10%) can utilize pure N2 for its low calibration reference gas.
Q) What is the span calibration cycle? Could you give me some explanations about span calibration?
A) The span cal cycle consists of a high point calibration preceded by adjustment of the analog absorption gain for full scale input to the A/D converter. Span cal is useful if you intend to restrict the O2 measurement range to some value less than 100%. For example, if you will never measure more than 50% O2, then a span cal at 50% O2 will increase the gain of the absorption channel for additional resolution. The gain increase is limited to about double the nominal gain at 100%. There is not much improvement in the O2 noise because the noise amplitude is much larger that the converter LSB, even at low gain.
Q) Would it be possible to have the X2004 loaded with a right-angled interface connector along the lines of Molex 70247 which is rated at 3A?
A) Our PCB layout would accept a right angle connector in place of the straight connector now installed. One side effect of this change is that the pin numbering for the interface is reversed because of the way the right angle pins are bent. If you are using a keyed connector then it would have to be rewired to properly mate with the right angle header. If the connector is unkeyed then you can just plug it in reversed. Note that installation of the right angle header is a rework task that will result in a charge by Oxigraf.
Q) What is the noise requirement of the power supply?
A) The X2000 sensors will operate with power supply ripple up to the following limits,
which are typical for switching power supplies:
- +12 Volt Supply: 11.4 to 15.8 volts, <200 mV ripple
- +5 Volt Supply: +4.5 to +5.25 volts, <150 mV ripple
Q) What about communication with the X2004, do you have any sample code to get us started?
A) Oxigraf would be more than happy to provide sample C software for X2000 customers. Feel free to contact us at:
238 East Caribbean Drive
Sunnyvale, CA 94089
Q) Do you have any suggestions as to correct grounding for the X2004?
A) The user interface connector is a standard 0.100 in centers, 16 pin header (3M 2516-6002UB or equivalent). The recommended mating connector is the Molex 22-55-3161 housing loaded with 16-02-0104 crimp terminals for #22 wire. It is recommended that all ground pins (2, 4, and 5) be used for power supply grounding.
Q) What about connecting to the analog outputs for the X2004?
A) Note that the analog output voltage is referenced to the system ground at the interface connector. High ground currents in the interface wiring due to the cell heater and thermoelectric cooler will cause an error in the analog voltage if it is not measured relative to the analog ground (interface pin 9). A differential amplifier connected to the analog output (pin 10) and analog ground (pin 9) should be used to reject the common mode offset due to ground current.