Vaisala Drycap DMT242 Manuel utilisateur

Vaisala DRYCAP®Dewpoint Transmitter DMT242

USER'S GUIDE 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:

2341

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

Vaisala DRYCAP®Dewpoint Transmitter DMT242

USER'S GUIDE June 2008 |M010036EN-D

5. Insert the wired screw terminal back into the connector excatly in the position indicated in Figure 3.

Push the fixing screw through the connector. Fasten the cable clamp. Insert the wired connector into

the counter connector.

NOTE The connection is incompatible if the positioning of the screw terminal is NOT as

indicated in Figure 3. Fasten the fixing screw.

6. Install the back cover allowing the cable to run through the hole in the cover. The transmitter is ready

for use.

NOTE When the power is switched on, wait about 7 minutes before taking measurements.

Start-up self-diagnostics freeze the output during the first operation minutes.

Figure 3 Wiring and Installation of Connector

CALIBRATION AND MAINTENANCE

Replacing the sintered filter

If the sintered filter is dirty it can prolong the response time of the measurement. If the filter needs to be

changed unscrew the filter and replace the old filter with a new one.

Calibration

It is recommended to perform a calibration check every other year. A field check can be carried out by

using a calibrated reference probe and comparing the readings measured with the transmitter and the

reference probe. The Vaisala DRYCAP®Hand-Held Dewpoint Meter DM70 is ideal for confirming the

performance of the transmitter in the field. By using a connection cable the readings of DMT242 and

DM70 can be viewed simultaneously on the display of DM70. If there is need for adjustement contact

Vaisala Instruments Service Centers or local Vaisala representative.

SCREW TERMINAL MUST BE INSTALLED TO THE

CONNECTOR IN THE POSITION OF THE FIGURE

(TERMINALS 2AND 3AS UPPER EDGE)

1= Connector

2= Screw terminal of the connector

3= Connector

4= Cable clamp

5= RS-232 serial port

6= Terminals 2 and 3

7= Three-wire cable

8= Pressure setting switches

9= Fixing screw

Vaisala DRYCAP®Dewpoint Transmitter DMT242

USER'S GUIDE June 2008 |M010036EN-D

SCALING THE ANALOG OUTPUT VIA THE SERIAL BUS

Serial communication settings

The analog output scaling can be done using the serial bus and computer with suitable terminal software.

Connect the DMT242 to a serial bus via the RS-232 interface by using the following settings: Baud rate:

2400, Parity: none, Data bits: 8, Stop bits: 1. The serial cable (DMT242RS) can be ordered from Vaisala.

Scaling of the dewpoint output

Scale the dewpoint parameter by giving the command ascl xx yy<ENTER> where xx = the low limit

(°C or ºF) and yy = the high limit (°C or ºF). The factory setting for serial measurement unit is

Centigrade (°C). To change the unit for Fahrenheit (ºF) use command unit xx <ENTER> where xx = n

for non-metric (ºF) and xx = mfor metric (°C) units.

ACCESSORIES

Order Code Description

HM47280 Stainless steel sintered filter

DMT242RS RS-232 serial line cable for PC (with female D connector)

210662 1/2" NPT adapter

GUARANTEE

Vaisala issues a guarantee for the material and workmanship of this product under normal operating

conditions for one (1) year from the date of delivery. Exceptional operating conditions, damage due to

careless handling and misapplication will void the guarantee.

Vaisala DRYCAP®Dewpoint Transmitter DMT242

USER'S GUIDE June 2008 |M010036EN-D

TECHNICAL SPECIFICATIONS

Dewpoint Temperature

Measurement range -80 ... +60 °C (-112 ... +140 °F)

DMT242A -80 ... +20 °C (-112 ... +68 °F)

DMT242B -60 ... +60 °C (-76 ... +140 °F)

DMT242X free scaling

When the dewpoint is below 0 C, the transmitter outputs

frost point.

Dewpoint accuracy with

DRYCAP®180M ±2 ºC (±3.6 ºF)

(See figure below)

Response time 63 % [90 %] at 20 °C gas temperature at

flow rate > 1 l/min and 1 bar pressure:

-60 →-20 °C Td(-76 →-4 °F Td) 5 s [10 s]

-20 →-60 °C Td(-4 →-76 °F Td) 45 s [10 min]

DRYCAP®180S ±2 ºC (±3.6 ºF)

(See figure below)

Operating Environment

Temperature 0 ... +60 ºC (32 ... +140 ºF)

Higher temperature peaks Short term OK

Relative humidity 0 ... 100 %RH

Pressure 0 ... 20 bara(0 ... 290 psia)

Sample flow rate no effect

Output

Analog output 4 ... 20 mA

Resolution for analog output ±0.002 mA

Typical temperature dependence 0.0008 mA/ºC

Serial line for service use RS-232

General

Sensor DRYCAP®180M

Operation voltage 17 ... 35 VDC

20 ... 28 VAC

Power consumption 24 VDC max 220 mA

External load for current

output

max 500 Ω

Optional connection cable

with DMT242 connector

2 m or 10 m

Connector for supply voltage

and signal output

Max wire size 0.75 mm2

Max wire diameter 6.5 mm/PG7

Service cable for serial line DMT242RS

Probe material stainless steel

(AISI 316L)

Sensor protection stainless steel sintered

filter (HM47280)

Mechanical connection G1/2" ISO228-1 thread

with bonded seal ring

(U-seal)

Electronics housing plastic (ABS/PC)

Housing classification IP 65 (NEMA 4)

Storage temperature range -40 ... +70 ºC

(-40 ... +158 ºF)

Complies with EMC standard EN61326-1:1997 +

Am1:1998 + Am2:2001; Industrial Environment.

Figure 4 Dimensions in mm [inches]

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