Epson XDT Single Point Self Calibration, manual or scheduled

XDT User’s Manual

The instrument will retain the calibration even if the power is turned off.

Under certain conditions, an over (super) saturated sensor may need to be completely dried out before a calibration is performed. Symptoms of these conditions are a sensor that will not go through the SpanCheck™ function to the END display, or a sensor that will not dry down after cal- ibration. To dry, install sensor in either a known dry gas stream i.e. instrument quality air or dry nitrogen, or place sensor in a dry can or bottle of desiccant and seal the container from outside air (the shipping container is designed for this purpose). After a minimum dry out period of 24 hours, proceed with the calibration procedure of your choice.

SpanCheck™ calibrates sensors by using micro climates. Please contact your representative if you have any questions about how to create such micro climates.

A perfectly acceptable and accurate for calibration micro-climate may be created for the XTR100 and XTR65 sensors by cupping the sensor in the palm of one’s hand during the SpanCheck™ pro- cedure. Remember that the micro-climate does not have to be accurate, it just has to be higher than the designed saturation level. The dewpoint of the micro-climate within the fingers is usually higher than the dewpoint of the room air and probably well above the +20°C upper range of the sensor. On a dry day, one may need to exhale in the hand before cupping the sensor to guarantee a high dewpoint. The sensor should be warmed up close to body temperature before performing this procedure. Care must be taken that the sensor temperature is not below the temperature of the hand, as in such case condensation could occur and super saturate the sensor. For the same reason, avoid exhaling directly onto the sensor.

3.4.4.3.2 Single Point Self Calibration, manual or scheduled

The instrument is calibrated at the factory with the sensor it is shipped with and does not need to be re-calibrated prior to installation.

Single point calibrations should be performed whenever the measurement is in question, or on a scheduled basis depending on the application. Consult with your representative to establish crite- ria for specific applications.

The single point calibration is performed on the premise that the sensor is exposed to a gas with a known dewpoint for a time sufficient to equilibrate. Then the sensor output is measured, and the calibration curve is adjusted to provide measurement computations which correspond to the known dewpoint. Measurements over the full sensor range are linearly adjusted to this known point.

The single point calibration provided by this instrument may be performed manually, or (when a sample system is ordered equipped with an electrically actuated switchover valve) unattended on a repetitive timer scheduled basis. The user interface for both is the same, with additional steps for interval setting and automatic stabilization time outs for the instrument with the electrically actu- ated valve.

Manual Single Point Self Calibration procedure for instruments without electrically actu- ated switchover valve:

•Refer to the unshaded area of the flow diagram on the second page of Appendix A.

•Expose the sensor to a known dewpoint

•Wait at least 15 minutes for the sample system to be stable, if the known gas is of a low dew-

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