Page 7
3.
PRINCIPLES of OPERATION
The Computrac
®
VAPOR PRO
®
Rx
utilizes a cylinder shaped bottle heater, a dry air-carrier
gas flow system and a moisture sensor. The instrument heats a sample of test material contained
in a 20 ml septum bottle or sealed freeze dried container. Volatiles, driven off from the sample,
are carried by the air system through the sensor block containing the Relative Humidity (RH)
sensor. The RH sensor used to detect water in the gas stream is a polymer capacitor relative
humidity sensor. The reading from this sensor is combined with sensor block temperature and
carrier gas flow data in a microprocessor to generate an accurate measurement of the moisture
content in the sample. The instrument then displays the result in terms of:
•
Parts per million (ppm) H
2
O,
•
Micrograms (
µ
g) H
2
O, or
•
Percentage (%) H
2
O.
Test parameters such as temperature, ending criteria, and purge time can be changed to optimize
test speed and accuracy. See Appendix A, beginning on page 47, for detailed specifications and
operating limits.
Computrac
®
VAPOR PRO
®
Rx Basic Flow System
