Super Systems 1500 VRSD - Manual (Page 10)

Model 1500 VRSD Operations Manual
Super Systems Inc. Page 10 of 28
13.0 Verify the 11.3% (Zero) calibration
13.1 Leave the sensor in the 11.3%RH calibration salt.
13.2 Record the temperature and the dew point of the sensor. Since there is
no display on the instrument, you will need to measure the voltage from the
microprocessor board and translate that into the appropriate measurement.
13.2.1 To determine the sensor temperature, measure the DC voltage
between pins 5(+) and 9(-) on the microprocessor board. The
voltage will be between 0 and 1VDC. Use the chart in Appendix C to
determine the temperature in °F, or use Appendix D to determine
the temperature in °C.
13.2.2 Temporarily record the sensor temperature.
13.3 Look up this temperature in Appendix “A” (Determining the Dew Point
in °F) or Appendix “B” (Determining the Dew Point in °C). Appendix A will
show the temperature values in Fahrenheit, and Appendix B will show the
temperature values in Celsius.
13.4 Next to the appropriate sensor temperature, note the number in the
corresponding column titled “11.3%”. This will match the measured dew
point, which can be verified wherever the dew point is displayed.
14.0 Determine the acceptability of the reading.
14.1 The value printed on the chart in Appendix A is a theoretical value, and
some variation can be expected. When a calibration is performed at SSi, we
certify (in writing) that the unit displays within +/- 1 degree of the theoretical
value after it has been calibrated. We would not consider a calibration to be
successful unless it is within +/- 1 degree, however in the case of a field
calibration, this degree of accuracy may or may not be required. The degree
of accuracy that is acceptable is determined by the policy of the person
performing the calibration.
NOTE: Keep in mind that the VRSD only displays whole numbers, and not
tenths of a degree. Therefore, a reading of 18°F could be as low as 17.50 or
as high as 18.49.
15.0 Allow the sensor to achieve equilibrium at ambient atmosphere.
15.1 After the 11.3% (Zero) calibration has been completed, remove the sensor
from the calibration salt and replace the cap.