HMW70U/Y
Operating Manual
HMW70U/Y-U191en-1.2
2
1996-08-16
CONNECTION TO AN AC SUPPLY
HMW70U/Y transmitter
Controller
VAC
VAC
Us
GND
signal
RH/T
GND
Us
RH/T
signal
HMW70U/Y transmitter
Figure 3: The recommended AC connection
HMW70U/Y transmitter
HMW70U/Y transmitter
Controller
shared
common line
VAC
GND
GND
Us
Us
RH/T
RH/T
signal
signal
Figure 4: A common loop formed in an AC
connection
The HMW70U/Y transmitters can also be
connected to an AC supply without an
external rectifier. However, when more
than one transmitter is connected to one
AC transformer, a common loop is
formed and there is an increased risk of a
short-circuit. To avoid this, use a
separate floating supply for each
transmitter (see Figure 3). However, if
several transmitters have to share one
transformer, the phase (~) must always
be connected to U
s
connector in each
transmitter (see Figure 4).
ONE-POINT RH CALIBRATION
The accuracy is recommended to be
checked at least once a year; the interval
depends on the operating conditions and
the required accuracy of the
measurement. When checking the
transmitter calibration, use the HMI41
indicator provided with an appropriate
probe and optional calibration cable. If
adjustment is necessary, use the humidity
offset potentiometer.
REPLACEMENT OF THE HUMICAP
SENSOR
Remove the damaged sensor and insert a
new one. Handle the sensor by the plastic
socket. Recalibrate the transmitter.
