Vaisala DMT242 - Manual

Vaisala DRYCAP ® Dewpoint Transmitter DMT242
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June 2008 | M010036EN-D
INTRODUCTION
DMT242 is a dewpoint transmitter for wide range of OEM applications. DMT242 measures dewpoint
with excellent long term stability which is maintained automatically with the patented auto-calibration
procedure. The Vaisala DRYCAP
® polymer sensor technology used in DMT242 is also durable against
dew in case condenced water exists in the process during system malfunction. The product mechanics
have been designed for harsh environments requiring protection against dust, dirt and splashed water.
The disconnection and reconnection of the transmitter is easy with the connector where the output signal
and supply voltage wires are connected. The unit also has a serial line for rescaling the analog output.
PRESSURE SETTING PROCEDURE FOR PRESSURIZED PROCESSES
For achieving the most accurate measurements
in pressurized processes, set the process
pressure to DMT242 according to Figure 1 by
using the pressure switches (see Figure 3, item
8). As shipped from factory, the pressure
switch setting is 1 bar, as in switch number 4 in
the ON position.
MOUNTING
1. Insert the sealing washer (see Figure 1) on
the probe and set the probe through the
fitting of the process pipe. The probe has
G½" ISO 228/1 parallel thread.
2. Fasten the transmitter to the fitting of the
process pipe by tightening from the nut of
the probe (24 mm).
WIRING
1. Remove the cover.
2. Take out the connector.
3. Take out the screw terminal from the
connector by pushing it out, for example,
with the fixing screw.
4. Use a three-wire cable. Suitable 2 m or
10 m optional cable is available from
Vaisala (items: 221475 for 2 m cable and
221476 for 10 m cable). Connect the wires
to the connector terminals as follows:
2 3 4 1
Switches Pressure (absolute)
2 … 4
0 … 2
12 … 14
4 … 6
8 … 10
10 … 12
14 … 16
6 … 8
18 … 20
16 … 18
(bar)
Figure 1 Pressure Setting Table
Figure 2 DMT242
Terminal nr 1 = V supply + (VAC line)
Terminal nr 2 = V supply - (VAC neutral)/signal -
Terminal nr 3 = Signal +
Leave the ground terminal free
+
-
THE SWITCH MARKED WITH
A BLACK SQUARE IS IN
THE
ON POSITION
1 = Cover
2 = Connector
3 = Flat gasket
4 = Counter connector
5 = Transmitter body
6 = Nut
7 = Sealing washer
8 = Probe
Wire colours in cables
221475 and 221476:
1 = brown
2 = blue
3 = black