RHapid-Cal Humidity Generator
Calibrate UUTs
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External Reference Probe Use
Use an external reference probe inserted into one of the chamber door ports to
perform calibrations tied to the uncertainty of the external probe. This is
necessary when the mixing insert is removed to accommodate larger UUTs, or to
obtain lower uncertainties in the calibration. A membrane-type sensor or chilled
mirror can be used for an external reference. The air flow within the chamber
should be sufficient for most remote chilled mirror probes such that an external
pump is not necessary. Match the depth of the external reference to the UUT
probe depth whenever possible.
Sample In/Out Ports
The humidity within the working chamber can be measured with a chilled mirror
that does not have a remote probe by drawing gas samples out of the chamber
using the Sample In/Out ports at the front of the Product. Use an external pump
capable of generating a flow of 0.5 liters per minute. The gas sample dew point
must be below the ambient temperature to avoid condensation on the Sample
In/Out port lines, otherwise the lines must be heated to 5
°
C above the chamber
temperature. Fluke Calibration recommends that the gas sample is returned back
to the Product through the Sample In port.
Measure the temperature within the chamber and the dew point measurement
from the chilled mirror to determine the relative humidity inside the Product
chamber. For the best performance, use stainless steel or PTFE tubing for all
connections to the Sample In/Out ports.
Temperature Extremes
The Product has guaranteed specifications using its internal reference for
chamber temperatures from 18
°
C to 28
°
C, 7 % to 95 % RH (see
Specifications
for exact points). Chamber temperatures outside of this range can be generated,
but an external reference probe should be used.
When a UUT or reference probe is inserted through the door, stem conduction
should be considered at the extremes of the Product generating range (for
example, chamber conditions below 18
°
C or above 28
°
C). At these extremes,
condensation may form at cold spots in the system. To avoid condensation,
place the entire UUT measurement head inside the chamber with an extension
cable. Place insulation around the door to help prevent condensation.
