Manual

Chapter 5 _______________________________________________________________ Calibration
CHAPTER 5
CALIBRATION
This chapter provides you with information that is intended to help you
calibrate this product.
Vaisala recommends a recalibration of the HMM211 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 three hours for
stabilization if the sensor head is in such an environment that the
warming function has been active. The warming function can be
deactivated by connecting the jumper to any calibration connector (see
Figure 5 on page 25). Note also that when humidity calibrating a Td
transmitter, the Td signal on Channel 2 is replaced by the RH signal 0
... 100 %RH with the chosen output range. For example, if the Td
output range is 0 ... 5 V, the output during RH calibration is 0 ... 100
%RH < > 0 ... 5 V.
- Calibration of a module with chemical purge option 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 3 minutes, and remove the filter. Allow to stabilize and
perform the calibration.
NOTE
Do not turn the power off during calibration.
VAISALA _______________________________________________________________________ 21