Vaisala hmt120 - Push-Button Calibration

6.2 Push-Button Calibration
C
A
L
RH
T
ADJ
+
SERVICE PORT
485-
GND
REL
C
A
L
RH
T
ADJ
+
ON 1 2
485 TERM
485+
SGND CH1 CH2
SHEILD
VIN-
VIN+
Figure 16 Adjustment Buttons
You can calibrate and adjust the transmitter with the adjustment buttons on the transmitter
motherboard. The two-point humidity adjustment is carried out by using two relative humidity
references: for example saturated salt points 11 % RH (LiCl) and 75 % RH (NaCl). The
dierence
between the two humidity reference points must be at least 30 %RH. The dierence between
the two temperature reference points must be at least 30 °C.
In push-button calibration, the transmitter outputs are by default relative
humidity in the range 0…100% RH in CH1 and temperature in the range -40…
+80°C in CH2 regardless what the actual transmitter settings are. Outputs mean
in this case both the display and analog current outputs.
6.2.1 Adjusting Humidity and Temperature with Push Buttons
The instructions here apply to both 1-point and 2-point calibration.
To make a humidity or temperature adjustment:
1. Open the transmitter cover. There are 3 buttons marked ADJ, + and - on the motherboard.
There are also two indicator LEDs, one green and one red.
2. Press the ADJ button and hold it down until the green indicator LED begins to blink slowly
(800ms cycle time).
Chapter 6 – Calibration and Adjustment
53