Vaisala HMM211 - Manual (Page 23)

Chapter 5 _______________________________________________________________ Calibration
The following numbers refer to Figure 4 above:
1 = For calibration with the HM70 or HMI41, insert the jumper as
indicated here.
2 = Calibration connector for the HM70 or HMI41
NOTE The serial communication parameters are:
1200 bauds, no parity, 8 data bits, 1 stop bit
NOTE When the connection is being established, the message 'CON ERROR'
blinks on the HMI41 display for a couple of times after which
measurement readings appear. This is quite normal and requires no
action; however, if the message is not replaced by measurement readings,
it is an indication of an operation error.
With Pushbuttons and a Jumper
You can also perform the calibration with pushbuttons and a jumper on
the component board (see Figure 5 on page 25). In addition, you need a
digital multimeter (DMM). There are two pushbuttons (UP and DOWN)
and six pairs of pins (RH offset, RH gain, T offset, T gain, Ta offset, and
Ta gain) that are connected with the calibration jumper. Vaisala
recommends using the RH offset pins if the RH is less than 65 %RH and
the gain pins if the RH is greater than 65 %RH.
For example, to perform a one-point humidity calibration using saturated
NaCl salt solution at 75.5 %RH as a reference, do as follows:
1. Insert the probe into a NaCl salt chamber and let stabilize.
2. Connect a DMM to the RH output and wait until the reading
stabilizes.
3. Connect a jumper to the RH gain pins and adjust the DMM reading
with buttons UP and DOWN until the output corresponds to
75.5 %RH.
4. Disconnect the jumper.
Two-Point Humidity Calibration
You can also perform a two-point calibration with saturated salt
calibrators (for example HMK15), or you can send the instrument to
Vaisala or a Vaisala representative for recalibration. See contact
VAISALA _______________________________________________________________________ 23