Vaisala HMM213 - Manual (Page 31)

Chapter 6 _______________________________________________________________ Calibration
CHAPTER 6
CALIBRATION
This chapter contains information that is needed to calibrate this product.
Vaisala recommends a recalibration of the HMM213 module after six
months of use. After the first recalibration, the recommended calibration
interval is approximately 12 months. However, please note that these
intervals depend on the operating conditions and the required accuracy.
When calibrating humidity instruments, it is important that the probe, the
reference instrument, and the calibrator are in thermal equilibrium.
Therefore, always allow enough time for stabilization before starting the
actual calibration.
- Calibration in the chamber: leave the calibrator (for example, the
HMK15) in the chamber overnight with the chamber door open.
- Calibration of a humidity and temperature module: allow at least one
hour for the stabilization of the calibrator (for example, HM70 hand-
held humidity and temperature meter with a reference probe).
- Calibration of a dewpoint module or of a humidity and temperature
module with two sensor heads: allow at least 3 hours for stabilization
if the sensor head is in such an environment that the warming function
has been active.
- Calibration of a module with chemical purge option: chemical purge is
activated when the power is connected. When calibrating a probe, turn
the power on with the sintered stainless steel filter on the probe, wait
for 10 minutes, and remove the filter. Let stabilize and perform a
calibration. NOTE: do not turn the power off during calibration.
NOTE When calibrating a module with the warmed sensor head,
deactivate first the heating by using command
HEAT 0 . If the
sensor head is in such an environment that the warming function has
been active, allow at least 3 hours for stabilization. After calibration,
the heating is reactivated with command
HEAT 1 .
VAISALA _______________________________________________________________________ 31