ROTRONIC Hygrogen2 - Manual (Page 61)

E-M-HG2-S-V2.1
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroGen2 Humidity and Temperature Generator:
Instruction Manual
Appendix
Instruction Manual for Software
Version 2.1
Document Type
Page 57 of 75
Document title
Disadvantages:
• Regular mirror cleaning is required to maintain best possible performance.
• Mirror measuring heads generate heat when cooling the mirror. Certain older chilled mirror
probes fitted through the HygroGen2 door can introduce temperature gradients.
• For dew points above ambient conditions, sample lines must be heated to avoid condensation
which can introduce instability.
• Chilled mirrors may be more expensive to calibrate than RH probes.
• Longer stabilisation time.
Without doubt, a chilled mirror reference can obtain the best possible calibration uncertainty, but
they do require a good level of user expertise to ensure the best possible results. Always follow the
chilled mirror manufacturer’s best practice recommendations and check the instrument’s
compatibility with the HygroGen2 operating specifications.
Practical Guidance - Chilled Mirror Reference
Depending on the conditions being measured, some chilled mirrors do require a longer time to
stabilise, sometimes up to 90 minutes.
Attention should be paid to the following:
• Some types of chilled mirror sensors have the tendency to over- or under-shoot, to “hunt”
and can be off-the-mark for quite a long period of time.
• At values below freezing, the indications of chilled mirror instruments without a force frost
feature can be ambiguous; readings may correspond to either the dew point or the frost point.
• Whenever measuring conditions result in a dew point that is higher than the laboratory
conditions, heat the entire external sample loop, including the sensor head. Heating is
required to avoid condensation.
For advice on choosing the most appropriate chilled mirror instrument, please consult your ROTRONIC
dealer.
Chilled mirror probes
Chilled mirror probes of diameters up to 50mm can be directly fitted through the HygroGen2 door.
Depending on the diameter of the probe, a special adaptor or custom HygroGen2 door may be
required, please contact your ROTRONIC dealer for guidance.
© 2014; Rotronic AG E-M-HG2-S-V2.1