Teledyne Temperature Control Check, Thermal Conductivity Analyzer, Model 212R

Thermal Conductivity Analyzer Model 212R

Checkaspreviouslystated,theanalyzersentiresamplingsystemhasbeen checked under pressure with a leak detector. However, if the external system checksoutandtheinstrumentisdisplayingalargediurnaloruni-directionaldrift, the interior sampling system should be checked for leaks. Do not open the analyzerinnerdoor. Usethefollowingprocedure:

1)Acquire a source of cylinder helium and through a dual stage regulator connect it to a length of 1/8" tubing.

2)Open the outer door of the analyzer and insert the tubing be- tween the edge of the sample control panel and the outer case.

CAUTION: Do not insert the tubing along the edges of the larger swing-down control panel as there is danger of obstructing the fan or short circuiting the electronics. The end of the tubing should be shaped into a curve so that the foam lining is not overly disturbed and the tubing should only be inserted a couple of inches into the interior.

3)Start the helium flowing. Keep the flowrate low so as not to disturb the temperature equilibrium of the analyzer interior.

4)Observe the recorder. If any leaks are present in the interior sampling system, the recorder will be driven off scale in one direction or the other. NOTE: The analyzer should be on Range #1 and the zero control adjusted so that the recorder is reading mid-scale. The direction the recorder indication moves is a function of the type of zero and reference gas being used (which varies per application) and which path of the sampling system (sample or reference) the leak is located in. If the recorder responds to an atmosphere of helium within the analyzer, all connections inside the analyzer must be checked.

6.4.2 Temperature Control Check.

The interior temperature of the analyzer is regulated to a constant value to within .002 degrees centigrade. The actual temperature control pointvaries slightly per application and is a function of the components used in the propor- tionaltemperaturecontrolcircuit.

If the recorder is displaying a large diurnal recording that is related to the time of day in termsof the differential between dayand night ambient tempera- ture,troubleinthetemperaturecontrolcircuitryisindicated. Again,thissymp-

22 Teledyne Analytical Instruments