Troubleshooting

 

WARNING!   When troubleshooting, follow all proper safety precautions. Use proper eye protection and hand protection at all times.

 

If problems are encountered in operation, it is necessary to verify the integrity of the probe and its supporting equipment, the control instrument, signal transmission lines, or the process, including the controlling elements, such as solenoid or motor driven valves.  If there is disagreement between the probe’s indicated value and dew point analysis, the following simple tests can be conducted to eliminate the probe as a source of problems.  The probe must be at temperature and under stable control.

 

• Reference air flow 0.5 to 1.0 CFH

 

• Sample flow 2.0 to 3.0 CFH

 

• Check the probe resistance.  It should be less than 10 kilohms.  If not, burn off the probe and retest.

 

• Test the speed of response after switching the control instrument to manual control.  First, record the mV output.  Then short the probe for 5 seconds, remove the short and measure the time required to return to within 1% of the original reading.  If it exceeds 30 seconds, conduct a burnoff and repeat the test after the reading has stabilized.

 

• Turn off the reference air supply for three minutes.  Read the probe millivolts, and then turn the air back on.  If the reading changes (immediately) by more than 25 mV, replace the probe.  The substrate is cracked or broken.

 

If these fundamental tests show that the probe is functional, check the following possible reasons for disagreement:

 

• Contamination of the reference air supply with combustibles

 

• Air leak into the sample line.  Check with a dew pointer at the probe entry

 

• Faulty insulation in the signal lines

 

• Instrument out of calibration.  Check with a DVM or calibrator that the instrument reading matches the open loop probe or temperature reading.

 

If you experience problems and cannot find the solution after troubleshooting, please call SSi Technical Support at (513) 772-0060.