Vaisala DMP248 OPERATING MANUAL

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DMP248 Dewpoint

Transmitter

OPERATING

MANUAL

M210492EN-A

JULY 2003

PUBLISHED BY Vaisala Oyj Phone (int.): (+358 9) 894 91

P.O. Box 26 Fax: (+358 9) 8949 2227 FIN-00421 Helsinki Finland

Visit our Internet pages at http://www.vaisala.com/

means, electronic or mechanical (including photocopying), nor may its contents be communicated to a third party without prior written permission of the copyright holder.

The contents are subject to change without prior notice.

_________________________________________________________________________CONTENTS

Table of contents

CHAPTER 1 GENERAL INFORMATION.......................................................................................................1

SAFETY................................................................................................................................................................1

WARRANTY .........................................................................................................................................................1

CHAPTER 2 PRODUCT DESCRIPTION.........................................................................................................3

GENERAL CHARACTERISTICS...............................................................................................................................3

THE OPERATING PRINCIPLE OF THE DMP248.......................................................................................................4

Use in high pressure.......................................................................................................................................6

CHAPTER 3 INSTALLATION...........................................................................................................................7

SELECTING THE PLACE OF INSTALLATION............................................................................................................7

MOUNTING THE TRANSMITTER ............................................................................................................................7

Mounting; overview.......................................................................................................................................9

Mounting the probe directly to the process..................................................................................................10

Installing the probe through the ball valve assembly...................................................................................11

Mounting the probe with a quick connect....................................................................................................17

Sample cell...................................................................................................................................................18

Grounding....................................................................................................................................................20

Connections..................................................................................................................................................22

Connection to an AC supply........................................................................................................................23

CHAPTER 4 COMMISSIONING.....................................................................................................................25

SECURITY LOCK JUMPER....................................................................................................................................25

SELECTING THE ANALOGUE OUTPUTS................................................................................................................26

CONNECTING THE RS 232C SERIAL BUS............................................................................................................28

CHAPTER 5 COMMANDS...............................................................................................................................33

COMMANDS AND SECURITY LOCK JUMPERS.......................................................................................................33

LED COMMANDS...............................................................................................................................................34

DISPLAY/KEYPAD COMMANDS...........................................................................................................................35

CHAPTER 6 CALIBRATION AND ADJUSTMENT.....................................................................................55

HUMIDITY CALIBRATION AND ADJUSTMENT......................................................................................................55

Two-point calibration and adjustment adjustment procedure ......................................................................56

Using serial commands.............................................................................................................................................56

Using display/keypad commands..............................................................................................................................57

Using LED commands..............................................................................................................................................58

Humidity calibration table............................................................................................................................59

TEMPERATURE CALIBRATION ............................................................................................................................59

One point offset correction...........................................................................................................................59

Using serial commands.............................................................................................................................................59

Using display/keypad commands..............................................................................................................................60

Using LED commands..............................................................................................................................................60

Two-point temperature calibration and adjustement....................................................................................61

Using serial commands.............................................................................................................................................61

Using display/keypad commands..............................................................................................................................62

Using LED commands..............................................................................................................................................62

CALIBRATION OF THE ANALOGUE OUTPUTS.......................................................................................................63

Using serial commands................................................................................................................................63

Using display/keypad commands.................................................................................................................63

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Using LED commands .................................................................................................................................64

CHAPTER 7 MAINTENANCE.........................................................................................................................67

REFERENCE MEASUREMENTS.............................................................................................................................67

SELF-DIAGNOSTICS............................................................................................................................................67

TEMPERATURE CHANNEL ADJUSTMENT WITH PT 100 SIMULATORS ...................................................................68

MEASUREMENT OF OUTPUT CURRENTS USING TEST POINTS ...............................................................................70

ADJUSTING THE CONTRAST OF THE DISPLAY......................................................................................................71

VAISALA SERVICE CENTERS ..............................................................................................................................71

CHAPTER 8 TECHNICAL DATA ...................................................................................................................72

MEASURED VARIABLES......................................................................................................................................72

OUTPUTS............................................................................................................................................................73

GENERAL...........................................................................................................................................................74

ELECTRONICS ....................................................................................................................................................75

SERIAL INTERFACE MODULES.............................................................................................................................75

ELECTROMAGNETIC COMPATIBILITY .................................................................................................................76

CHAPTER 9 OPTIONS......................................................................................................................................76

CHAPTER 10 SPARE PARTS AND ACCESSORIES ....................................................................................77

APPENDIX 1 SERIAL COMMANDS...............................................................................................................79

APPENDIX 2 POWER SUPPLY MODULE ..................................................................................................101

APPENDIX 3 INSTALLING AND USING THE RS 485/422 SERIAL PORT MODULE.........................105

APPENDIX 4 INSTALLING AND USING THE CURRENT LOOP MODULE........................................115

APPENDIX 5 ERROR MESSAGES................................................................................................................125

APPENDIX 6 WIRING DIAGRAM................................................................................................................129

APPENDIX 7 ALARM OUTPUT UNIT .........................................................................................................131

APPENDIX 8 PRESSURE CONVERSION CHART.....................................................................................137

PRESSURE CONVERSION CHART........................................................................................................................137

Multiplication factors .............................................................................................................................................137

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CHAPTER 1_______________________________________________________ GENERAL INFORMATION

CHAPTER 1 GENERAL INFORMATION

Safety

Throughout the manual important instructions regarding the safety considerations are focused as follows.

WARNING

CAUTION

NOTE

Warranty

Warning denotes a hazard. It calls attention to a procedure, practice, condition or the like, which, if not correctly performed or adhered to, could result in injury to or death of personnel.

Caution denotes a hazard. It calls attention to a procedure, practice, condition or the like, which, if not correctly performed or adhered to, could result in damage to or destruction of part or all of the product.

Note highlights important information. It calls attention to an essential procedure, practice, condition or the like.

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 __________________________________________________________________________1

CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION

CHAPTER 2 PRODUCT DESCRIPTION

General characteristics

The DMP248 transmitter is a microprocessor-based instrument for the measurement of dewpoint temperature in low humidities. The transmitter measures other quantities as well: relative humidity, temperature and ppm concentration (dry). When the dewpoint temperature is below 0 °C, the transmitter calculates the frostpoint instead of the dewpoint. The dewpoint output can be scaled freely, for example, dewpoint -40...+20 °C can be set to correspond to 0...1 V. The DMP248 transmitter has two analogue outputs and can be connected to a serial bus via the RS 232C interface or optionally through an RS 485/422 serial module or a current loop module.

The transmitter can be configured in many ways. It can have either a blank cover or a cover with a local display and keypad with which the user can operate the transmitter. The power supply voltage can be selected from three alternatives (24 VDC/VAC, 115 VAC, 230 VAC). Two analogue output signals are selected from the measured quantities; the signals can be scaled. The transmitter can be supplied with two, five or ten metre sensor head cable. The alarm output option enables two separate alarms that can be freely set by user.

Options Alarm output 2 relays 8A/230V SPCO relays Power supply 24 VDC (VAC) (standard), 115/230 VAC Serial interface RS 232C (standard), RS 485/422, current loop Display cover cover with or without local display & keypad Cable length 0.56, 2, 5 or 10 metres

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The operating principle of the DMP248

The DMP248 transmitter incorporates the DRYCAP® sensor which is optimized to be used in low humidities but has also an excellent tolerance against condensation. The DRYCAP® sensor uses an operating principle based on changes in capacitance as its thin polymer film absorbs water molecules together with a combined temperature measurement with a Pt 100 resistive temperature sensor. The capacitance of the thin polymer film has a direct response proportional to RH, but combined with the temperature signal the response of the DRYCAP® sensor is rather proportional to Pw (water

vapour pressure) or to the dewpoint. While frostpoints (dewpoints below 0 °C) in principle can be

determined by using traditional RH transmitters, it is very difficult considering the required accuracy at the dry end calibration. As relative humidity levels approach zero the accuracy rapidly decreases and the offset soon becomes the largest source of errors when monitoring frostpoints. Therefore, the focus is to minimize the offset (error at 0% RH) when monitoring the process gas.

For example to monitor a process with a frostpoint of -40 C and a temperature of +20 C translates to a relative humidity of 0.55%. An offset error of -0.2 %RH, which is well within specifications for a normal RH-transmitter, brings the measured RH down to 0.35%. This would bring the calculated frostpoint down to -44 C. Thus seemingly minor offset errors caused by drift or bad calibration translate into unacceptable frostpoint errors when the RH is low.

To solve the accuracy problem the DMP248 transmitter utilizes a patented method that automatically adjusts the dry end measurement in frostpoints. The offset calibration algorithm incorporated into the DMP248 transmitter uses the fact that the capacitance of a thin film polymer sensor is proportional to RH as seen in formula 1.

RH RH Gain

= +

out

Pws T

( )

(2-1)

where: RH0=output in completely dry state

Pw=water vapor pressure Pws(T)=temperature dependent water vapor saturation pressure

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CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION

0.4

The function Pws(T) is well known from literature. Thus, it is possible to determine the offset (RH0) if measurements are made at

two or (preferably) more temperatures assuming a constant Pw during the process.

0.3

20°C

0.2

0.1

RHout(%)

-0.1

-0.2

-0.3 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

FIGURE 2-1 Device output during hypothetical offset calibration

30°C

1/Pws(T)

cycle.

For example, for a transmitter with a -0.2%RH offset error is made 11 measurements at temperatures 20...30 °C. The frostpoint is assumed to stay constant at -40 °C and that the 'Gain' is nominal 100%.

As the temperature increases the RH drops. Since the response is linear, a straight line is fitted through the data points. The line

intercepts the y-axis at RH0 as shown in FIGURE 2-1. Now the RH0 is known and it can be subtracted from the indicated value 0.35% RH to get the correct value of 0.55% RH.

FIGURE 2-2 shows the DRYCAP



sensor as mounted on a DMP248 probehead. Through a combination of the polymer sensor and Pt 100 sensor, the DRYCAP will accurately measure the water vapor pressure used in determining low dewpoints. During auto-calibration the Pt 100 element is used to first heat and then measure the temperature of the sensor while cooling back to ambient temperature. A complete cycle of auto-calibration takes 60...70 seconds. When the auto-calibration cycle is active, the transmitter locks the output values to those measured prior to auto-calibration.

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OPERATING MANUAL_______________________________________________________________

FIGURE 2-2 The DRYCAP

Note that the auto-calibration takes place only if the DMP248 is used in ambient humidities below 10 %RH (dewpoint below -12 °C at 20 ° C) and at ambient temperature 0...+80 °C.

Use in high pressure

If the process pressure differs from the normal ambient pressure, the value has to be entered in the transmitter memory to ensure the best possible measurement accuracy. The pressure setting is used for pressure compensation of the DMP248 transmitter. Note that although dewpoint is a pressure dependent parameter, this setting cannot be used for calculating dewpoints in different pressures. The probe should be installed to a place with pressure equal to that of the process in order to ensure the most reliable measurement. For converting pressure units, see Appendix 8.

NOTE

The probe can be installed in the process through the ball valve assembly provided that the process pressure is less than 10 bars. This way, the process does not have to be shut down when installing or removing the probe. However, if the probe is not removed from the process as such (e.g. the process is shut down first), the process pressure can be max. 20 bars.



sensor mounted on a DMP248 probe.

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CHAPTER 3_______________________________________________________________INSTALLATION

CHAPTER 3 INSTALLATION

Selecting the place of installation

Select a place which gives a true picture of the environment or process; also select a place that is as clean as possible. Air should circulate freely around the sensor.

It is recommended that the sensor head is installed directly in the process through the ball valve assembly. When the ball valve assembly is used, the chamber or the duct does not have to be emptied or shut down for installation or removal of the probe. Install the sensor head transversely against the direction of the process flow.

If the probe head has to be installed aside of the process gas flow or the process is very hot or particularly dirty, the probe can be installed in a “leak-through” position. In this installation, the probe is mounted behind the ball valve assembly and if necessary, a cooling coil and/or a filter can be mounted in between. The flow passes through the sensor head and leaks out through a vent hole in the fitting body enabling a reasonable response time. In hot and dirty processes, a sample system can also be used.

Mounting the transmitter

In FIGURE 3-1 and FIGURE 3-2, you can see the dimensions of the DMP248 transmitter:

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OPERATING MANUAL _______________________________________________________________

PROBE UP

PROBE PUSHED DOWN

cable length 2, 5 or 10 m

ø5.5

178

ø13.5

adjustment

range120 mm

R1/2 ISO 7/1

non leaking screw (A) (factory setting) or leak screw (B) (included in the package)

149

clasp nut

fitting body

NOTE

104

ENT

120

ø6.5

133

145

FIGURE 3-1 Dimensions of the DMP248 electronics housing (in

mm).

1. Always mount the transmitter housing with the cable bushings

pointing downwards to ensure IP65 (NEMA4) rating

2. Make sure that the connection cable has the right thickness

(∅7...10 mm) and that the cable bushing is carefully tightened.

3. Pay always special attention to closing the transmitter cover

carefully and remember to tighten all four screws.

FIGURE 3-2 Probe dimensions (in mm).

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CHAPTER 3_______________________________________________________________INSTALLATION

NOTE

Take care not to damage the pipe of the probe. If the pipe is damaged, the probe head is less tight and it will not go through the clasp nut.

Mounting; overview

sealing with:

1. LOCTITE® No 542 + activ. No 7649 (t=-55...+150 °C)

2. MEGA-PIPE EXTRA No 7188 (t=-55...+170 °C)

3. PTFE tape (t=-60...+210 °C) NOTE: the tape does not lock the parts together. Therefore, use two fork spanners (hex 24 and 27 mm) for tightening and opening the clasp nut of the probe

FIGURE 3-3 Sealing and thread cutting for the fitting body.

The fitting body can be installed e.g. on standard pipe fittings (G 1/2 ISO 228/1) or on a thread in the process wall. If the wall thickness is less than 10.5 mm, it is recommended to use a welded sleeve (see

FIGURE 3-3). Note that the minimum recommended distance of the

fitting body and probe head is 40 mm (see FIGURE 3-3).

fitting body hex = 24mm tapered thread R1/2 ISO 7/1

parallel thread G1/2 ISO 228/1 (BS 2779, JIS B0202)

ø19mm drilling

>10.5mm

>40mm

Process or pipe wall

Adjust the probe to a suitable distance according to the type of installation, and tighten the clasp nut first manually. Then, mark the fitting body and the clasp nut and tighten the nut a further 50...60° with a fork spanner (see FIGURE 3-4).

probe

a pen

fitting body

FIGURE 3-4 Tightening the clasp nut.

clasp nut

60°

max.

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OPERATING MANUAL_______________________________________________________________

NOTE

Be careful not to tighten the clasp nut more than 60° as this may result in difficulties when trying to open it.

The probe is delivered with non-leaking screw A mounted. For bypass measurements, this screw is removed and replaced with leaking screw B (included) and an O-ring is placed on the groove of the sintered filter prior to installation. Make sure to tighten the screw carefully.

Screw B has a small (0.08 mm) laser-made hole in the middle; the gas or air to be measured passes through the sintered filter and by the sensor, and leaks out through the screw.

Mounting the probe directly to the process

Select a point, which gives a true picture of the process. The transmitter can be installed directly in the process wall, especially if the pressure of the process is 1 bar (atmospheric processes).

process wall

recommended adjustment range

25 mm

FIGURE 3-5 Installing the probe in an atmospheric process.

25...135 mm

Leave at least 25 mm (1 ") of probe head free to enable a faster response time in unpressurized processes

welded sleeve (G1/2, Ø 40 mm)

non leaking screw (screw A, factory setting)

If the probe is installed in process pipes where the water is likely to collect at the measurement point, take care to install the sensor head so that it will not be immersed in water.

When the probe is installed directly on the process wall or pipe, note that a closing valve may be needed on both sides of the installed probe so that the sensor head can be removed from the process for calibration and maintenance.

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CHAPTER 3_______________________________________________________________INSTALLATION

If the sensor head is installed in a pressurized chamber, always make sure that the pressure of the chamber is equalized with the ambient pressure prior to removing the probe.

capped nut DIN 917-M22x1.5

when the probe is pulled out for maintenance, cap the hole with a capped nut; this way, the process can be open although the probe is not in place

sealing

welded sleeve

(G1/2)

process pipe

FIGURE 3-6 Installing the sensor head directly on the process pipe.

Non leaking screw (screw A)

closing valve (ball valve)

Installing the probe through the ball valve assembly

The best way to install the sensor head is through the ball valve assembly. Use a 1/2” ball valve assembly with a ball hole of ∅14 mm or more. In this kind of installation, it is not necessary to empty or shut down the process for installing or removing the sensor head. If the sensor head is installed in a process pipe, please note that the nominal size of the pipe must be at least 1 inch. See FIGURE 3-7 -

FIGURE 3-8 for detailed instructions.

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probe

non-leaking screw A

handle

>30 mm

ball of the ball valve (hole diameter at least 14 mm)

NOTE

process pipe / chamber

FIGURE 3-7 Installing the sensor head through the DMP248BVS

ball valve assembly.

The probe can be installed in the process through the ball valve assembly provided that the process pressure is less than 10 bars. This way, the process does not have to be shut down when installing or removing the probe. However, if the process is shut down before removing the probe, the process pressure can be max. 20 bars.

See FIGURE 3-8- FIGURE 3-11 for detailed description of installation through the ball valve assembly. This installation is possible provided that the process pressure is less than 10 bars. Note also that if the sensor head is installed in a process pipe, the nominal size of the pipe must be at least 1 inch.

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CHAPTER 3_______________________________________________________________INSTALLATION

• STEP 1: mount the probe with the ball valve assembly closed;

tighten the clasp nut manually.

bushing R1/2 cone/G1/2(40 bar) e.g. Camozzi 2520-1/2-1/2

(the bushing serves for moving the probe (sinter) to such a distance from the ball valve that the valve can be closed)

clasp nut

fitting body R1/2 cone, sealed

ball valve 1/2" (40 bar) e.g. Atlas Copco:BAL-1A 15 (G1/2)

FIGURE 3-8 Installing the probe through the ball valve assembly;

>30 mm

bushing R1/2 cone sealed

nipple R1/2 cone sealed

step 1.

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• STEP 2: open the ball valve assembly.

manual press tool

120mm

probe pipe

148 mm

ø5.5

handle

ball of the ball valve

adjustment range

> 14

ø14

marking groove

leak screw (B) (hex. 1.5 mm)

(40)

R1/2 ISO 7/1

ø13.5

fitting ferrule

clasp nut (hex 27 mm)

fitting body (hex. 24 mm)

O-ring

DRYCAP® sensor

filter

FIGURE 3-9 Installing the probe through the ball valve assembly;

step 2 (measures in mm).

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CHAPTER 3_______________________________________________________________INSTALLATION

STEP 3: push the probe head through the ball valve assembly into the process. If the pressure is high, use a manual press tool. Note that the sensor head must be pushed so deep that the filter is completely inside the process flow.

MANUAL PRESS TOOL

VALVE OPEN

VALVE CLOSED

FILTER

FIGURE 3-10 Installing the probe through the ball valve assembly;

step 3.

For by-pass measurements, the probe is mounted behind the ball valve assembly and non-leaking screw A on the fitting body is replaced with leaking screw B and O-ring is placed on the groove of the sintered filter. Screw B has a small (0.08 mm) laser-made hole in the middle; the gas or air to be measured passes through the sintered filter and by the sensor, and leaks out through the screw. The process pressure reduces in the hole of the screw B. This installation is recommended if the process flow rate is >20 m/s and there is over-pressure in the process.

VAISALA _________________________________________________________________________15

OPERATING MANUAL _______________________________________________________________

gas escape channel: use this position for by-pass measurements

leak screw (B)

sintered filter

O-ring

DRYCAP® sensor

process pipe or chamber

NOTE keep the marking groove in sight when using leak screw (B)

FIGURE 3-11 Installing the sensor head for by-pass measurements.

When pushing the probe head through the ball valve assembly, be careful not to break the sintered filter. Open and close the ball valve assembly with the marking groove always in sight. In by-pass measurements, the clasp nut is tightened manually prior to pressing the probe through the valve. When the probe has been pressed through and the valve is open, the nut is tightened 50...60° with a fork spanner (hexagon 27 mm).

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CHAPTER 3_______________________________________________________________INSTALLATION

Mounting the probe with a quick connect

The probe can also be installed with a quick-connect, which acts as a closing valve between the process and the probe. The installation can be easily done even in small ducts with standard parts, and the probe is easily removed when necessary. It is necessary for the probe to be installed in the leak-through position for a reasonable response time.

FIGURE 3-12 illustrates an example of using a quick connect with the

DMP248 probe. The chamber can be made of stainless steel AISI 316.

keep the marking groove in sight when using leak screw

leak screw

15 mm

30 mm

chamber made of hexagonal bar (hex=27 mm)

sealing

G1/2

50 mm

G1/8 or G1/4

bayonet socket

fitting part

of the quick-

connect

process pipe

FIGURE 3-12 Installing the probe with a quick-connect.

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Sample cell

It may be necessary to use the sample cell if the process (e.g. a pipe) is too small for the DMP248 sensor head. Furthermore, if the process is very hot (>80 °C) or particularly dirty, the probe is installed in a sample cell behind a cooling coil and/or filter. In this case, the ambient temperature must be at least 10 °C warmer than the process dewpoint in order to avoid condensation in the sample tubing.

G1/4

ISO

228/1

PUSH PROBE

INTER AGAINST

THIS EDGE,

TIGHTEN THE

G1/4

Sample gas inlet

use connector

R1/4 ISO 7/1

SAMPLE CELL

CLASP NUT.

DMP248SC

G1/2

ISO228/1

OUT

view

A - A

Sample gas outlet

use connector R1/4 ISO 7/1

FIGURE 3-13 Dimensions (in mm) of the DMP248SC sample cell.

for DMP248 probe

fixing screws

(e.g. M6x60 or 1/4" x 11/4")

TOP VIEW SIDE VIEW

FIGURE 3-14 Fastening to a metal plate (top view) and on a concrete

frame (side view)

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CHAPTER 3_______________________________________________________________INSTALLATION

process pipe

G1/4

ISO

228/1

SAMPLE CELL

DMP248SC

CLASP NUT.

THIS EDGE,

PUSH PROBE

TIGHTEN THE

INTER AGAINST

G1/4

screw

FRONT VIEW TOP VIEW

metal hose clamp

thread M6 or 1/4"-20 UNC

metal

plate

thickness e.g.

3mm (1/8")

AISI 316

Dimensions of the metal plate

FIGURE 3-15 Fastening to a process pipe with the help of a metal

plate

An overpressure in the process is necessary to create a flow through the sample cell. Note that the pressure of the sample cell must not differ from that of the process because dewpoint temperature changes with pressure. In dirty processes, it may be necessary to use a filter between the cooling coil and the sample cell. One more simple way of using the sample cell with user provided accessories is shown in

FIGURE 3-16. The flow through the sample cell is controlled with the

needle valve and the pressure is kept equal to that of the process.

FIGURE 3-16 Installing the probe in high temperatures (an example).

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Grounding

A single electrical cable with a screen and three to ten wires is recommended for power and analogue output/serial bus connections. The cable diameter should be 7...10 mm.

The screen of the electrical cable must be grounded properly to achieve best possible EMC performance. Recommended cable shield is done in the cable gland as shown.

• remove the brass disks, rubber ring and nut from the transmitter

housing

• strip 165 mm of the cable insulation, but leave 25 mm of the braid

visible

• slip the nut and rubber ring over the cable insulation

• slip the brass disk that has the bigger hole in it over the braid so

that it rests against the cable insulation

• slip the other brass disk over the wires to the middle of the braid

flexible wires 0.5 mm²

(AWG 20), stranded wires

recommended

140

165

braid

brass disks

rubber ring

nut

cable

D = Ø 7...10 mm

(If the cable diameter is less

than 7mm, use a shrinking

tube or an adhesive tape)

shielding tube

braid

brass disks

• push back the braid and press it between the two brass disks to

achieve a full 360° grounding; the fold between the disks should have the same diameter as the brass disks

• secure the braid with a shielding tube

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CHAPTER 3_______________________________________________________________INSTALLATION

• insert the wires into the transmitter housing through the gland

• tighten the nut

• connect the wires into the screw terminals and fasten a cable tie

around the wires

cable tie

transmitter housing

gland

brass disks

rubber ring

nut

NOTE

When the cable is grounded as explained, the metallic parts of the sensor head, the screen of its cable, the transmitter housing and the screen of the signal cable to external system are all connected to each other. After this, the whole system can be grounded from one point only. If the grounding is made via several points (sensor head, transmitter housing, signal cable), make sure that the different groundings are made to the same grounding potential. Otherwise, harmful grounding currents may be generated. If you do the grounding via the transmitter housing, use one serrated lock washer between a mounting screw and the housing; the lock washer breaks the paint on the housing.

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Connections

CH1- and CH2- are connected

CH2

CH1+

CH1 -

CH2 -

together internally

OPENED COVER OF THE DMP248

CURRENT/VOLTAGE

OUTPUTS

POWER SUPPLY (INTERNAL OR EXTERNAL)

Do not use power supply ground (-) as output signal ground

24 V +

FIGURE 3-17 Electrical connections

Power supply 24 VDC

24 VAC (see Chapter Connection to an AC supply)

Output signals 0...20 mA

4...20 mA

0...1 V

0...5 V

0...10 V

Power supply ground (-) is connected to the housing with parallel connection of 15 nF capacitor and 300 kΩ resistor.

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CHAPTER 3_______________________________________________________________INSTALLATION

Connection to an AC supply

The DMP248 transmitter can also be connected to an AC supply without an external rectifier. However, when more than one transmitter is connected for example to one 24 VAC transformer, a common loop is formed and there is an increased risk of a shortcircuit. To avoid this, always use separate floating supply for each transmitter (see FIGURE 3-18A). However, if several transmitters have to share one transformer, the phase (∼) must always be connected to + connector in each transmitter (see FIGURE 3-18 B).

A) NO COMMON LOOP FORMED - RECOMMENDED

DMP248 transmitter Controller

24 VAC

DMP248 transmitter

B) COMMON LOOP FORMED -

DMP248 transmitter

24 VAC

supply

voltage

supply

voltage

DMP248 transmitter

signal

supply

output

voltage

signal

output

voltage

NOT RECOMMENDED!

Controller

signal

output

signal

output

shared common

line

FIGURE 3-18 Connecting the transmitter to an AC supply.

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CHAPTER 4_____________________________________________________________COMMISSIONING

CHAPTER 4 COMMISSIONING

When the DMP248 transmitter leaves the factory, its measurement ranges and output signals have already been selected. The user can subsequently change the measurement units between metric and nonmetric and select and scale the output signals with software functions, see Chapter Selecting and scaling the analogue output quantities and Appendix 1.

Security lock jumper

Before the settings can be changed, the user must first remove the security lock jumper in connector X15 (see FIGURE 4-1). The security lock jumper makes it impossible to change the transmitter settings by mistake. The jumper should be removed only for changing the settings and for calibration; the auto-calibration is active only with the jumper connected. When the security lock jumper is connected, some commands cannot be used (see Chapter Commands and security lock jumpers).

CHANGE OF SETTINGS DISABLED

X15

OPENED COVER OF THE DMP248

FIGURE 4-1 Location of the security lock jumper.

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OPENED COVER OF THE DMP248

Selecting the analogue outputs

The DMP248 transmitter can be ordered ready with the current or voltage outputs required. If the outputs need to be changed, move the jumpers in connector X15 into positions as shown in FIGURE 4-2.

CH1

CH2

C H 2

C H 1

CURRENT OUTPUTS 0 ... 20 / 4 ... 20 mA

CH2

CH1

C H 1

C H 2

VOLTAGE OUTPUTS 0 ... 5 V / 0 ... 10 V

CH2

CH1

C H 2

C H 1

VOLTAGE OUTPUTS 0 ... 1 V

CH2

CH1

C H 1

C H 2

CH1 0 ... 1 VOLTAGE OUTPUT CH2 CURRENT OUTPUT

X15

FIGURE 4-2 Selecting the analogue outputs with jumpers.

The software also has to be informed which outputs are in use. This is done either through the serial interface or the menus on local display when in use. The serial command is AMODE and the display/keypad command "Mode ð Analog outputs ð Mode" (see Chapter 5

commands). If the outputs need to be scaled, see serial

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command ASCL and the display command "Mode ð Analog outputs ð Scale".

All jumpers are used only with the 0...1 V outputs. When other outputs are in use, the spare jumpers are kept in connector X55.

X55 spare jumpers

OPENED COVER OF THE DMP248

FIGURE 4-3 Spare jumpers

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Connecting the RS 232C serial bus

RX GND

TX NC

OPENED COVER OF THE DMP248

FIGURE 4-4 Serial bus connections.

To connect a PC to the DMP248 transmitters via the RS 232C serial bus, one of the following cables is required. The type of cable depends on the terminal and the connector type.

RXD

TXD

TX GND RX

DMP248

TERMINAL

D9S

D25S

D25P

2 5 3

4 6 7 8

3 7 2

5 6 8

3 7 2

FIGURE 4-5 Three connection examples.

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When the serial bus has been connected between the PC and the transmitter, the PC is switched on. When using a PC, a terminal emulation programme (e.g. HyperTerminal, Procomm Plus, Datastorm or Windows terminal) is started.

The factory settings for data transfer are:

• 4800 baud

• even parity

• 7 data bits

• 1 stop bit

• full duplex

NOTE

When the serial bus settings are changed, the transmitter has to be reset before the new settings become effective.

The processor does not allow the following combinations:

• no parity, 7 data bits, 1 stop bit: if this combination is given the

DMP248 programme will change the number of stop bits to 2.

• even or odd parity, 8 data bits, 2 stop bits: if this combination is

given the programme changes the number of stop bits to 1.

Refer to the manuals of the PC and the terminal emulation programme when giving serial settings.

The RS 232C screw terminal cannot be used if an RS 485/422 serial module or a current loop module is used. See Appendices 3 and 4 on how to install and operate these modules.

In calibrating or changing the settings of the transmitter, it can be more convenient to use the connector X17, if connector X6 is already in use. This connector, however, transfers only RS 232C signals. If a RS 485/422 serial port module or a current loop module has been installed, it has to be removed before communicating through the X17 connector.

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RX GND TX

X17

FIGURE 4-6 Location and connections of connector X17.

NOTE

Some PC computers can generate interferences to the measured humidity and temperature values if the transmitter and the PC are connected to different mains outlets. To minimize the possibility of these interferences, always use the same main outlet (same phase of the main electricity) for the PC and the power supply of DMP248. It is always preferable to use the connector X6 instead of the connector X17 because it is more immune to interferences.

Reverting to factory settings of the serial port

If the serial port settings are not known, no commands can be given via the serial interface. The settings can be reverted to the factory settings by inserting a jumper in connector X16. The jumper must be inserted when the power is on!

X16

OPENED COVER OF THE DMP248

FIGURE 4-7 Forcing the serial port settings back to factory settings.

When the jumper is inserted the serial line factory settings become valid, but only temporarily. The transmitter must be given new

settings; otherwise, the transmitter uses the old, unknown settings after power-up. When the new settings have been given, the

transmitter must be reset. The jumper must be removed before the

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transmitter is reset; if the jumper is in place when power is turned on, the transmitter does not work.

After jumper insertion the transmitter is in STOP mode, ready to receive commands.

The same method is used when the transmitter is in POLL mode and the user has forgotten its address.

CAUTION

Inserting a jumper in any other place in connector X16 voids the guarantee of the transmitter.

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CHAPTER 5 COMMANDS

The DMP248 transmitter uses a microprocessor; therefore, its configuration can be set according to the user's needs. This is done through commands, either utilizing the menus on the local display or giving commands through the serial interface (see Appendix 1). Most often, the commands are used to change the settings of the two analogue channels.

A limited range of commands can be given with the three press switches - up, down and enter - inside the transmitter housing. Four LEDs indicate the command given with the up and down switches. LED commands can be used to calibrate the transmitter (both humidity and temperature) or to calibrate the analogue outputs.

A full range of commands can be given through the display/keypad or through the RS 232C serial bus. The commands can be used e.g. to select and scale the outputs, to calibrate the humidity and temperature channels as well as the analogue outputs and to set the serial interface.

Commands and security lock jumpers

In order to prevent any tampering with the transmitter settings, the transmitter cannot be calibrated, the analogue outputs set or the analogue output quantities selected or scaled unless the security lock jumper has been disconnected. The commands involved are:

• all LED commands (except DCAL)

• display/keypad commands:

Cali ð RH T

Analog outputs

Mode ð Analog outputs ð Mode

Scale

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• serial commands:

CRH, CT, FCRH, ACAL; AMODE, ASEL, ASCL

In the following, the description of these functions is preceded with a reminder of the security lock jumper:

Disconnect the security lock jumper!

LED commands

NOTE

If the transmitter has a display/keypad cover, the LED commands cannot be used.

DOWN

ENT

OPENED COVER OF THE DMP248

FIGURE 5-1 Location of press switches and LEDs

press switches

LEDs

Use the up and down switches (marked with arrows on the printed board) to find the desired command code and acknowledge it with the ENT switch. The command codes are (l = lit, ¡ = dark):

¡¡¡¡ (0) return to normal state ¡¡¡l (1) relative humidity calibration ¡¡l¡ (2) temperature calibration ¡¡ll (3) calibration of analogue outputs l¡¡l (9) forced auto-calibration (one auto-calibration; the

security lock jumper must be connected)

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Display/keypad commands

Display mode

In the display mode, the transmitters output measurements on the display; different quantities can be scrolled with the arrow keys. The first line is scrolled with button σ and the second line with button τ; all selections are stored with ENTER. The selected quantities appear on the display also after power failure. After the reset, the transmitters are always in the display mode.

The display also shows error messages and alarms if they occur.

Command mode

Press the CL key to enter the command mode. The first display is the main menu:

The commands can be scrolled with the arrow keys. The currently active command flashes; a command is selected with the ENT key. When a menu is displayed, either the first command or the currently valid setting flashes. The CL key takes the transmitter back to the display mode.

Entering numbers

When the transmitter needs numbers to be entered into the programme (e.g. when scaling or setting the analogue outputs, in calibration or when giving the transmitter an address), the field is either empty or the currently valid figure is displayed. Any previously given value is deleted with the CL key.

When the field is empty, a cursor blinks at the right side of the display. Pressing the arrow keys brings either a blank (), a comma (,), a dash (-), a full stop (.) or a number from 0 to 9 on the display. The right character is selected with ENT; after that, the number or numbers move left one step. Entering numbers is ended with selecting a blank () and pressing ENT. The last character entered can be deleted with CL. If CL or ENT key is pressed when the field is empty, the program returns to the previous display.

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With some commands (e.g. calibration) the figures are changed using the arrow keys. When an arrow key is pressed continuously for a while, the numbers start changing at an increasing rate.

Auto-calibration

NOTE

Normally auto-calibration parameters do not have to be changed.

• Select More in the main menu and then again More in the second More menu. Select Dry cal and then Settings.

• The interval parameter defines the frequency of auto-calibration cycles. When the transmitter is turned on, the first auto-calibration takes place after an hour unless the frequency has been set to less than an hour. After the first auto-calibration, the set frequency is activated and the auto-calibration takes place e.g. every six hours. If the setting is correct, press ENT.

• If the setting needs to be changed, press CL and change the setting with arrow keys; acknowledge the setting with ENT. If the setting is changed, it becomes valid only after the next auto-calibration has been completed. If you wish to activate it immediately reset the transmitter or turn it off.

• This parameter defines the maximum allowed change of the dewpoint value during the pre-defined dTdp time. If the change in dewpoint value exceeds the limit, the calibration is not started. The auto-calibration is done only after process is stabilized. The transmitter retries untill the calibration is succesfully complited.

• If the setting is correct, press ENT.

• If the setting needs to be changed, press CL and change the value

with arrow keys; acknowledge the setting with ENT.

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• This parameter defines the measuring time of the change in dewpoint prior to the auto-calibration (see the parameter Max dTdp).

• If the setting is correct, press ENT.

• If the setting needs to be changed, press CL and change the value

with arrow keys. Acknowledge the setting with ENT.

• This parameter defines the maximum correction (%RH) the transmitter does during each auto-calibration cycle. If the correction exeeds the limit, the calibration is ignored. If the setting is correct, press ENT.

NOTE

• If the setting needs to be changed, press CL and change the value with arrow keys; acknowledge the setting with ENT.

• This parameter defines the time the output values prior to the auto- calibration are frozen after the calibration. The time is for sensor temperature stabilization.

• If the setting is correct, press ENT.

• If the setting needs to be changed, press CL and change the value

with arrow keys; acknowledge the setting with ENT.

Auto-calibration takes place only when the security lock jumper is connected. During auto-calibration, the reading on the display is frozen.

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NOTE

Forced auto-calibration

• Select More in the main menu and then again More in the second More menu. Select Dry cal and then Calibration

• Select More in the main menu and then again More in the second More menu. Select Dry cal and then Calibration. The following is displayed:

• If you press any key, the calibration is interrupted. If no key is pressed, the calibration takes place immediately. The text above is displayed during the calibration. If the process is unstable (see Chapter Auto-calibration) or relative humidity is over 10%, the calibration is not performed. The text above is only shortly displayed and the display returns to the measuring mode. The calibration is not performed again even if the maximum correction is exceeded.

Calibration... press any key to abort

Analogue output commands

Selecting the output (mA/V)

Disconnect the security lock jumper!

• Select Mode in the main menu and Analog outputs in the Mode menu:

• Select Mode ( mA / V ). The current settings for channel 1 are displayed:

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• If the settings are correct, press ENT.

• If the settings need to be changed, press CL:

− the quantity (mA/V) starts flashing; it can be changed with the

arrow keys and acknowledged with the ENT key

− the lower limit starts flashing

− acknowledge the lower limit with ENT or start changing it by

pressing CL; a new lower limit is given one character at a time with the arrow keys

− the upper limit starts flashing

NOTE

− acknowledge the upper limit with ENT or start changing it by

pressing CL; a new upper limit is given one character at a time with the arrow keys

When channel 1 has been set, the programme goes on to channel 2; the procedure is the same as with channel 1.

Also the analogue output jumpers must be set to correct places (see

FIGURE 4-2)

Selecting and scaling the analogue output quantities

Disconnect the security lock jumper!

• Select Mode in the main menu and Analog outputs in the Mode

menu:

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• Select Scale. The quantity and scaling for channel 1 are displayed:

• If the settings are correct, press ENT.

• If the settings need to be changed, press CL:

− the quantity starts flashing; it can be changed with the arrow

keys and acknowledged with the ENT key

− the lower limit starts flashing

− acknowledge the lower limit with ENT or start changing it by

pressing CL; a new lower limit is given with the arrow keys

− the upper limit starts flashing

− acknowledge the upper limit with ENT or start changing it by

pressing CL; a new upper limit is given with the arrow keys

− When channel 1 has been set, the programme goes on to

channel 2; the procedure is the same as with channel 1.

Output via serial bus

Turning the serial interface echo ON/OFF

Select More in the main menu, select More in the More menu, then again More and then Echo.

• Use the arrow keys to select the right alternative and press ENT.

Serial bus settings

• Select Seri in the main menu; the currently valid serial interface settings are displayed:

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• If the settings are correct, press ENT; the programme returns to the

display mode.

• If the settings need to be changed, press CL:

• Select the parameter to be changed with the arrow keys and ENT

key.

Selecting baud rate:

Selecting parity:

Selecting data bits:

Selecting stop bits:

Full duplex/half duplex:

The processor does not allow the following combinations:

• no parity, 7 data bits, 1 stop bit: if this combination is given the

DMP248 programme will change the number of stop bits to 2

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• even or odd parity, 8 data bits, 2 stop bits: if this combination is

given the programme changes the number of stop bits to 1

NOTE

The serial bus settings become effective only after reset.

Setting the transmitter address

Address is used when more than one transmitter is connected to one serial bus; it makes it possible to communicate with one transmitter at a time.

• Select More in the main menu and Addr in the More menu; the following is displayed:

• Pressing ENT returns the programme to the main menu.

• Pressing CL deletes the old address; enter the new address with

the arrow keys.

Selecting the output units

• Select Unit in the main menu:

• Use the arrow keys to select the right alternative and press ENT.

metric non-

metric RH %RH %RH T °C °F Td °C °F ppm

ppm ppm

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Output modes

The output modes only affect output through the serial interface: the transmitter accepts all display and LED commands irrespective of which serial output mode it is in. The DMP248 transmitter has three serial output modes: RUN, STOP and POLL.

In the RUN state the transmitter outputs measurements automatically through the serial interface to a PC or a peripheral. The only command that can be given through the serial interface is S (stop) which ends the RUN state.

In the STOP state serial commands are given to the transmitters. Measurements are then output only by entering command SEND.

The POLL state is used when more than one transmitter is connected to the same serial bus; a single transmitter can be addressed and communicated with. When the connection to the one transmitter is opened in the POLL state, the transmitter goes into STOP state and can then receive commands normally. Closing the connection returns the transmitter to POLL state. In POLL state the transmitter outputs measurement only when requested (with command SEND, see page

51). If the user has forgotten the address of the transmitter and the transmitter does not have a display, the transmitter has to be reverted to the factory settings. If the transmitter has a display, the settings can be checked through it.

Setting the serial interface operation mode

• Select Mode in the main menu; the following is displayed:

• Select Serial output:

• The currently valid setting flashes. Select the desired mode with

the arrow keys and press ENT. After this the programme returns to the Mode Menu.

• When Run mode is selected, the currently valid output interval is

displayed:

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The output interval setting can be changed as follows:

• press CL

• the number starts flashing

• if the interval needs to be changed, press CL again and enter the

new interval; otherwise press ENT

• the unit (s, min, h) starts flashing

• the unit can be changed with the arrow keys and acknowledged

with ENT

Others

• after this the programme returns to Mode menu

Pressure compensation

The pressure is used for pressure compensation of the DRYCAP sensor in order to ensure the best possible measurement accuracy. If the process pressure differs from normal ambient pressure, the value has to be entered in the transmitter memory. The pressure also has a considerable effect on the ppmv value. The pressure to be entered is the absolute pressure in hPa (for converting pressure units, see Appendix 8).

• Select Pres in the main menu and the following appears:



• Pressing ENT returns the programme to the main menu without

changing the pressure reading.

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jumper connected. If the security lock jumper is not connected, the

• If the pressure needs to be changed, press CL; enter the new

pressure with the arrow keys

NOTE

The pressure compensation takes place only with the security lock

pressure compensation is performed with the value 1013.25 hPa.

Setting the date

• Select More in the main menu; select Date in the More menu:

• If the date is correct, acknowledge it by pressing ENT; this takes

the programme back to the More menu.

• If the date needs to be changed, press CL.

− first the centuries (19) start flashing; use the arrow keys to

change them and press ENT

− the years (92) start flashing; use the arrow keys to change them

and press ENT

− the months (06) start flashing; use the arrow keys to change

them and press ENT

− the days (17) start flashing; use the arrow keys to change them

and press ENT

Setting the time

• Select More in the main menu; select Time in the More menu:

• If the time is correct, acknowledge it by pressing ENT; this takes

the programme back to the More menu.

• If the time needs to be changed, press CL.

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− first the hours (14) start flashing; use the arrow keys to change

them and press ENT

− the minutes (25) start flashing; use the arrow keys to change

them and press ENT

− the seconds (32) start flashing; use the arrow keys to change

them and press ENT

NOTE

The transmitter does not have a real-time clock with backup battery. This means that the date and time settings are not permanent.

Serial commands

More detailed descriptions of the serial commands can be found in Appendix 1. Here only the most commonly used command sequences are described. The instructions on how to connect the DMP248 transmitters to serial bus are given in Chapter Connecting the RS 232C serial bus.

Pressing ESC always interrupts any serial command being given. In the commands <cr> means carriage return.

Auto-calibration

NOTE

Normally auto-calibration parameters do not have to be changed.

DRYCAL<cr>

>drycal DCAL ON Interval min : 60 ? Max dTdp: 2.00 ? dTdp time s : 10 ? Max corr. : 0.040 ? Settl time s : 50 >

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The interval parameter defines the frequency of auto-calibration cycles. When the transmitter is turned on, the first auto-calibration takes place after on hour unless the frequency has been set to less than an hour. After the first auto-calibration, the set frequency is activated and the auto-calibration takes place e.g. every six hours. If the setting is changed, it becomes valid only after the next auto-calibration has been completed. If you wish to activate it immediately reset the transmitter or turn it off.

The Max dTdp parameter defines the maximum allowed change of the dewpoint value during the pre-defined dTdp time. If the change in dewpoint value exceeds the limit, the calibration is not started. The auto-calibration is done only after process is stabilized. The transmitter retries untill the calibration is succesfully complited. Note that normally, this parameter does not have to be changed.

The dTdp time defines the measuring time of the change in dewpoint prior to the auto-calibration (see the parameter Max dTdp).

NOTE

The Max corr. parameter defines the maximum correction (%RH) the transmitter does during each auto-calibration cycle.

The Settl time defines the time the output values prior to the autocalibration are frozen after the calibration. The time is for sensor temperature stabilization.

Normally, the Max dTdp and the Max corr. parameters need not be changed.

Auto-calibration takes place only when the security lock jumper is connected. With command <fst on>, the serial line printing indicates the stages of the auto-calibration (n = no auto-calibration, w,h,s = different phases in auto-calibration, S = settling time auto-calibration is on).

DCAL<cr>

>dcal Calibration... any key to abort > (appears when the auto-calibration

is completed in 60 - 70 seconds)

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If you press any key, the calibration is interrupted. If no key is pressed, the calibration takes place immediately. If the process is unstable or relative humidity is over 10%, the prompt (>) appears immediately. In that case the calibration is not performed. The calibration is not performed again even if the maximum correction is exceeded. (see Chapter Display/keypad commands)

Pressure compensation

PRES pppp.pp <cr>

where pppp.pp = absolute pressure (hPa). value has to be entered in the transmitter memory in order to ensure

the best possible measurement accuracy. The pressure setting is used for pressure compensation of the DMP248 transmitter. The pressure is given in hPa/mbar; for converting pressure units, see Appendix 8.

NOTE

When the command is given, the transmitter first gives the current pressure; after this the new value can be entered or the current one acknowledged.

>PRES <cr> Pressure : 1013.25 ? 1000.00 <cr>

When the current pressure is known, a new pressure can also be entered directly:

>PRES 1010 <cr> Pressure : 1010

If the security lock jumper is not connected, the pressure compensation is made with the value 1013.25 hPa.

If the pressure setting is frequently adjusted, e.g. by using an external barometer as a pressure input source, the command XPRES is recommended (see Appendix 1).

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Analogue outputs

Setting the analogue outputs

Disconnect the security lock jumper!

AMODE a bb.bbb cc.ccc d ee.eee ff.fff <cr>

a = channel 1: U = voltage output

I = current output bb.bbb = lower limit of channel 1 cc.ccc = upper limit of channel 1 d = channel 2: U = voltage output

I = current output ee.eee = lower limit of channel 2 ff.fff = upper limit of channel 2 The bb.bbb, cc.ccc, ee.eee and ff.fff parameters are entered in volts or

milliamperes. Example:

lower limit of channel 1 is 0 V and upper limit 1 V (U 0 1) lower limit of channel 2 is 2 V and upper limit 10 V(U 2 10)

>AMODE U 0 1 U 2 10 <cr> Ch1 : 0.000 ... 1.000 V Ch2 : 2.000 ... 10.000 V

Selecting and scaling the analogue output quantities

Disconnect the security lock jumper!

ASEL xxx yyy <cr>

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xxx = channel 1's quantity yyy = channel 2's quantity (RH, T, Td, ppm)

Example: dewpoint temperature selected on channel 1 and temperature on channel 2

>ASEL Td T <cr> Ch1 ( Td ) lo -50.00 'C ? -40<cr> Ch1 ( Td ) hi 10.00 'C ? 0<cr> Ch2 ( T ) lo 10.00 'C ? 0<cr> Ch2 ( T ) hi 100.00 'C ? 60<cr> >

Scaling the analogue outputs

Disconnect the security lock jumper!

Example: dewpoint is scaled in the range of -40...0 °C and temperature in the range of 0...+60 °C

>ASCL <cr> Ch1 ( Td ) lo -50.00 'C ? -40<cr> Ch1 ( Td ) hi 10.00 'C ? 0<cr> Ch2 ( T ) lo 10.00 'C ? 0<cr> Ch2 ( T ) hi 100.00 'C ? 60<cr> >

Output via the serial bus

Starting the measurement output

Starts output of measurements to the peripheral devices (RUN mode); the only command that can be used is S (stop).

ASCL <cr>

R <cr>

The output format can be changed with command FORM (see Appendix 1).

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Stopping the measurement output

S<cr>

Ends the RUN mode; after this command all other commands can be used.

Outputting the reading once

SEND <cr> in STOP mode

SEND aa <cr> in POLL state

aa = address of the transmitter when more than one

transmitter is connected to a serial bus (0...99)

Output:

Td= -9.3 'C PPM= 2733 T= 22.1 'C RH= 10.4 %RH Td= -9.3 'C PPM= 2730 T= 22.1 'C RH= 10.4 %RH

...

The output format can be changed with command FORM (see Appendix 1).

Setting the output interval for the RUN mode

INTV xxx yyy <cr>

xxx = output interval (0...255)

0: no pause between outputs

yyy = unit (s, min or h)

Example: output interval is changed into 10 minutes

>INTV 10 min <cr> Output intrv. : 10 min

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Serial bus settings

SERI b p d s x <cr>

b = bauds (300, 600, 1200, 2400, 4800, 9600) p = parity (n = none, e = even, o = odd) d = data bits (7 or 8) s = stop bits (1 or 2) x = duplex (H = half, F = full)

The settings can be changed one parameter at a time or all parameters at once:

>SERI O <cr> changing parity only 4800 O 7 1 HDX

>SERI 600 N 8 1 F <cr> changing all parameters 600 N 8 1 FDX

The processor does not allow the following combinations:

• no parity, 7 data bits, 1 stop bit: if this combination is given the

DMP248 programme will change the number of stop bits to 2

• even or odd parity, 8 data bits, 2 stop bits: if this combination is

given the programme changes the number of stop bits to 1

NOTE

The serial bus settings become effective only after reset. When the half-duplex mode is set, it will automatically turn the echo

off. Even then, the ECHO command can indicate that echo is on.

Selecting the output units

UNIT x <cr>

x = m / n

m= metric units (°C) n= non-metric units) (°F)

Setting the transmitter address

ADDR aa <cr>

aa = address (0...99) Example: transmitter is given address 99

>ADDR <cr> Address : 2 ? 99 <cr>

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Resetting the transmitter

RESET <cr>

Operating the transmitter via the serial bus

Setting the serial interface

SMODE xxxx<cr>

xxxx = STOP, RUN or POLL

In STOP mode: measurements output only by command, all

commands can be used

In RUN mode: outputting automatically, only command S can be

used

In POLL mode: measurements output only with command SEND.

When in POLL state, the output state is changed as follows:

OPEN aa <cr>

SMODE xxxx<cr>

aa = address of the transmitter xxxx = STOP, RUN or POLL

The OPEN command sets the bus temporarily in STOP state so that the SMODE command can be given. Example:

>SMODE STOP <cr> setting STOP state Serial mode : STOP

OPEN & CLOSE

OPEN nn <cr>

nn = address of the transmitter (0...99)

CLOSE <cr>

In STOP mode: command OPEN has no effect, CLOSE sets the

transmitter in POLL mode temporarily

In POLL mode: command OPEN sets the transmitter temporarily in

STOP mode, command CLOSE returns the instrument to POLL mode

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Example: relative humidity calibration is performed at transmitter

2 which is in POLL state

>OPEN 2 <cr> opens the line to transmitter 2 >CRH <cr> calibration started ... >CLOSE <cr> line closed

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CHAPTER 6 CALIBRATION AND

ADJUSTMENT

The DMP248 transmitter is fully calibrated and adjusted as shipped from factory. The recommended humidity calibration interval is one year.

A hand-held dewpoint meter DM70 can be used in field-checking of the DMP248.

The adjustments of the temperature measurement channel and the analogue outputs are particularly stable and in normal circumstances, there is no need to recalibrate them.

NOTE

To achieve the best accuracy in low dewpoints, the DMP248 shall be sent once a year to Vaisala Service Centers for dewpoint calibration and adjustment.

Humidity calibration and adjustment

The DMP248 transmitter is calibrated against two accurate RH references. The calibration can be performed by the end-user, or the instrument can be sent to Vaisala (see page 71) or a Vaisala representative. A two-point calibration and adjustment can be performed with Vaisala’s HMK15 Calibrator.

Calibration can be performed by giving the commands using the press switches inside the housing, through the serial bus (serial commands) or through the menus on the local display (display/keypad commands).

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When LED commands are used and when the two analogue channels do not output either relative humidity and/or temperature, relative humidity is calibrated on channel 1 and temperature is calibrated on channel 2. The calibration ranges are 0...100 %RH and -20...+80 °C. When the transmitter is calibrated at two points, the points must be either 50 %RH or 50 C apart from each other.

NOTE

As relative humidity is a temperature dependent parameter, the probe and the salt bath calibrator have to stabilize to the same temperature for best accuracy.

Two-point calibration and adjustment adjustment procedure

A two-point humidity calibrationand adjustment should be performed in stable conditions using saturated salt solutions as references.

Using serial commands

• Leave the calibrator and the transmitter for at least 4 hours in the

same space so that their temperatures have time to equalize. Remove the filter cap on the transmitter.

Disconnect the security lock jumper before turning the transmitter on!

• Place the sensor head in the calibration hole of the LiCl bottle (dry

end reference) in the humidity calibrator.

• Wait for 30 minutes.

• Give command CRH <cr>, enter the first point value and press

<cr>.

>CRH <cr> RH : xx.x Ref1 ? yy.y <cr> Press any key when ready...

• If you want to see how the sensor stabilizes to the humidity in the

calibrator, enter c <cr> instead of the first reference:

RH : 11.9 Ref1 ? c <cr> RH : 11.5 Ref1 ? c <cr>

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CHAPTER 6______________________________________________ CALIBRATION AND ADJUSTMENT

RH : 11.5 Ref1 ? 11.3 <cr> Press any key when ready...

• Place the sensor head in the calibration hole of the NaCl bottle

(wet end reference) in the humidity calibrator.

• Wait for 30 minutes.

• Press any key and enter the second point value and press <cr>.

RH : xx.x Ref2 ? yy.y <cr>

• The stabilization of the sensor can be monitored here as well by

entering c <cr> instead of the reference value.

Using display/keypad commands

• Leave the calibrator and the transmitter for at least 4 hours in the

same space so that their temperatures have time to equalize. Remove the filter cap on the transmitter.

Disconnect the security lock jumper before turning the transmitter on!

• Place the sensor head in the calibration hole of the LiCl bottle (dry

end reference) in the humidity calibrator.

• Select Cali in the main menu and then RH; select Not changed

and then two-point calibration RH 2 point cal. Change the first point reading with the arrow keys to correspond the reference humidity and press ENT; pressing an arrow once changes the reading by 0.05 %RH.

• Place the sensor head in the calibration hole of the NaCl bottle

(wet end reference) in the humidity calibrator.

• Wait for 30 minutes.

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OPERATING MANUAL_______________________________________________________________

• If necessary, change the second point reading with the arrow keys

and press ENT.

Using LED commands

• Leave the calibrator and the transmitter for at least 4 hours in the

same space so that their temperatures have time to equalize. Remove the filter cap on the transmitter.

Disconnect the security lock jumper before turning the transmitter on!

• Place the sensor head in the calibration hole of the LiCl bottle (dry

end reference) in the humidity calibrator.

• Connect an ammeter/voltmeter to the analogue outputs (connector

X2). Give command ¡¡¡l. At the first calibration point the LED on the left flashes; adjust the first point (offset) with the arrow switches to the value given in the calibration table and press ENT switch.

• Place the sensor head in the calibration hole of the NaCl bottle

(wet end reference) in the humidity calibrator.

• Wait for 30 minutes.

• Check that the reading corresponds within the desired accuracy to

that given in the calibration table. If not, adjust the second point with the arrow switches to the correct value and press ENT. At the second calibration point the second LED from the left flashes.

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CHAPTER 6______________________________________________ CALIBRATION AND ADJUSTMENT

Humidity calibration table

TABLE 6-1 Greenspan's calibration table

Temperature °C 15 20 25 30 35

°F 59 68 77 86 95

LiCl %RH * 11.3 11.3 11.3 11.3

4...20 mA 5.81 5.81 5.81 5.81

0...20 mA 2.26 2.26 2.26 2.26

0...1 V 0.113 0.113 0.113 0.113

0...5 V 0.565 0.565 0.565 0.565

0...10 V 1.13 1.13 1.13 1.13

NaCl %RH 75.6 75.5 75.3 75.1 74.9

4...20 mA 16.10 16.08 16.05 16.02 15.98

0...20 mA 15.12 15.10 15.06 15.02 14.98

0...1 V 0.756 0.755 0.753 0.751 0.749

0...5 V 3.780 3.775 3.765 3.755 3.745

0...10 V 7.56 7.55 7.53 7.51 7.49

*) If the LiCl solution is used or stored in temperature below +18 °C (+64 °F), the

equilibrium humidity of the salt solution changes permanently.

Temperature calibration

The temperature channel has been calibrated at the factory and since it is very stable, adjustment should be made only when there is strong reason to believe that the adjustments have changed.

Temperature calibration should be performed against some accurate temperature reference. It can be done either using the press switches inside the housing, through the serial bus or the menus on the local display. Either a one point offset correction or a two point calibration is possible.

One point offset correction

Using serial commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

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• Check the transmitter against the reference.

• Give command CT <cr>, enter the first point value and press <cr>:

>CT <cr> T : xx.x Ref1 ? yy.y <cr> Press any key when ready

• If you want to see how the sensor stabilizes to the reference

temperature, enter c <cr> instead of the first reference:

T : 0.90 Ref1 ? c <cr> T : 0.55 Ref1 ? c <cr> T : 0.55 Ref1 ? 0.0 <cr> Press any key when ready...

• After giving the correct temperature value (Ref1) and pressing

<cr> press any key and then <cr>.

Using display/keypad commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

• Check the transmitter against the reference.

• Select Cali in the main menu and then T; select one-point

calibration T 1 point cal.

• Change the reading with the arrow keys to correspond to the

reference and press ENT.

Using LED commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

• Check the transmitter against the reference.

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CHAPTER 6______________________________________________ CALIBRATION AND ADJUSTMENT

• Connect an ammeter/voltmeter to the analogue outputs (connector

X2). Give command ¡¡l¡. At the first calibration point the LED on the left flashes; adjust the first point (offset) with the arrow switches to the same reading with the reference and press ENT switch.

• After adjusting the offset point and pressing ENT the second LED

from left flashes. Press ENT without changing the output value.

Two-point temperature calibration and adjustement

Using serial commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

• Check the transmitter against the reference.

• Give command CT <cr>, enter the first point value and press <cr>:

>CT <cr> T : xx.x Ref1 ? yy.y <cr> Press any key when ready

• If you want to see how the sensor stabilizes to the reference

temperature, enter c <cr> instead of the first reference:

T : 0.90 Ref1 ? c <cr> T : 0.55 Ref1 ? c <cr> T : 0.55 Ref1 ? 0.0 <cr> Press any key when ready...

• Change the temperature and again check the transmitter against

the reference.

• Check that the reading corresponds with the reading of the

reference instrument. If not, adjust the second point.

• Press any key, enter the second point value and press <cr>.

T : xx.x Ref2 ? yy.y <cr>

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• The stabilization of the sensor can be monitored well by entering c

<cr> instead of the reference value.

Using display/keypad commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

• Check the transmitter against the reference.

• Select Cali in the main menu and then T; select two-point

calibration T 2 point cal. Change the first point reading with the arrow keys and press ENT.

• Change the temperature and again check the transmitter against

the reference.

• Check that the reading corresponds with the reading of the

reference instrument. If not, adjust the second point.

• If necessary, change the second point reading with the arrow keys

and press ENT.

Using LED commands

• Leave the reference instrument and the transmitter for at least 4

hours in the same space so that their temperatures have time to equalize. Remove the filter cap prior to calibration.

Disconnect the security lock jumper before turning the transmitter on!

• Check the transmitter against the reference.

• Connect an ammeter/voltmeter to the analogue outputs (connector

• Change the temperature and again check the transmitter against

the reference.

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• Check that the reading corresponds with the reading of the

reference instrument. If not, adjust the second point.

• If necessary, adjust with the arrow switches to the correct value

and press ENT. At the second calibration point the second LED from the left flashes.

Calibration of the analogue outputs

The analogue outputs have been calibrated at the factory and since they are very stable, calibration of the outputs should be performed only when there is reason to believe that their adjustments have changed.

Using serial commands

Disconnect the security lock jumper!

ACAL <cr>

The outputs on channels 1 and 2 are measured and the measured values (mA or V) entered as calibration coefficients.

Example: both channels have 0...10 V outputs (set with AMODE command); enter the voltages measured at the analogue outputs:

>ACAL <cr> Ch1 U1 ( V ) ? 0.123 <cr> Ch1 U2 ( V ) ? 9.98 <cr> Ch2 U1 ( V ) ? 0.120 <cr> Ch2 U2 ( V ) ? 9.98 <cr>

Using display/keypad commands

Disconnect the security lock jumper!

• Connect an ammeter/voltmeter to the output of channel 1, select

Cali in the main menu and Analog outputs in the Cali menu. The following is displayed (the quantity can be either mA or V):

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• Enter the measured lower end current/voltage on channel 1.

• Enter the measured upper end current/voltage on channel 1.

• Connect the meter to the output of channel 2 and enter the

measured lower end current/voltage on channel 2.

• Enter the measured upper end current/voltage on channel 2.

Using LED commands

If both the analogue outputs and humidity/temperature channels are calibrated, the analogue outputs should be calibrated first. This applies only when the calibrations are done using the LED commands!

• connect an ammeter/voltmeter to the analogue outputs (connector

X2)

Disconnect the security lock jumper!

• Give command ¡¡ll.

• the LED on the left flashes; set the low end of channel 1 with the

arrow keys and press ENT

• the second LED from the left flashes; set the high end of channel 1

with the arrow keys and press ENT

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CHAPTER 6______________________________________________ CALIBRATION AND ADJUSTMENT

• the LED on the left flashes; set the low end of channel 2 with the

arrow keys and press ENT

• the second LED from the left flashes; set the high end of channel 2

with the arrow keys and press ENT

The analogue outputs are calibrated to ensure that outputs are correctly scaled: for example, when the output is scaled to 4...20 mA, the low end of the scale is 4 mA and high end 20 mA exactly. However, when 0... 20 mA output is used, the output can not be adjusted to exactly 0 mA, but to 50 µA. When 0...1 V, 0...5 V or 0...10 V output is in use, the output is adjusted to 50 mV. The following table summarizes the correct output values.

TABLE 6-2 Summary of the correct output values

Output scale:

0...20 mA 4...20 mA 0...1 V 0...5 V 0...10 V low end: 50 µA 4 mA 50 mV 50 mV 50 mV high end: 20 mA 20 mA 1 V 5 V 10 V

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CHAPTER 7____________________________________________________________MAINTENANCE

CHAPTER 7 MAINTENANCE

Reference measurements

Reference measurements are needed to verify whether the transmitter readings are within specifications. This way the user can check if the transmitter needs calibration or service.

The reference measurement should be made as close to the checked sensor as possible and the readings should be read at the same time, when possible. A re-calibrated DMP248 transmitter can be used as a reference.

Self-diagnostics

The DMP248 transmitter goes through a self-diagnostics procedure when the power is switched on. If the procedure does not reveal any errors or faults, the transmitter starts operating normally. If errors or faults are found, check first if the DRYCAP sensor is damaged. If it is intact, send the transmitter to Vaisala or a Vaisala representative for repairs. The error messages the transmitter outputs are listed in Appendix 5.

If any errors occur during operation, the error messages are output on the local display if the transmitter displays measurements; if the menus are used, error messages are not output. The LEDs indicate errors at all times. During operation, however, the error messages are not output automatically through the serial interface. If there is any reason to doubt that there is something wrong with the transmitter, use command ERRS:

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ERRS <cr>

If there are no error messages, only a prompt is displayed:

>ERRS <cr> >

When errors have occurred, the transmitter outputs the error code (see Appendix 5 for all error messages):

>ERRS <cr> E40 f ( all ) out of range >

Temperature channel adjustment with Pt 100 simulators

Switch the power off and disconnect the wires to the Pt 100 sensor from solder lugs TP5, TP6 and TP7.

TP6

X88

FIGURE 7-1 Location of solder lugs TP5, TP6 and TP7 and

TP7

TP5

connector X88

Connect a Pt 100 simulator to connector X88 and set it at the lowest temperature to be calibrated.

Pt 100

X88

FIGURE 7-2 Connecting the Pt 100 simulator to connector X88

Switch the power on.

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CHAPTER 7____________________________________________________________MAINTENANCE

Adjustment using serial commands

Give command CT and enter the first point value and press <cr>:

>CT <cr> 'C : xx.x Ref1 ? yy.y <cr> Press any key when ready

Set the Pt 100 simulator at the highest temperature to be calibrated, and press any key. Enter the second point (gain) reference reading. If second reference is not needed, press <cr> to complete one point offset correction.

Adjustment using display commands

Select Cali in the main menu and then T; select two-point calibration T 2 point cal. Change the first point reading with the arrow keys and

press ENT. Set the Pt 100 simulator at the highest temperature to be calibrated,

and adjust the second point (gain) to the reference reading.

Adjustment using LED commands

Connect an ammeter/voltmeter to the analogue outputs (connector X2). Give command ¡¡l¡, and adjust the first point (offset) with the arrow switches to the same reading with the reference and press ENT switch.

Set the Pt 100 simulator at the highest temperature to be calibrated, and adjust the second point (gain) to the reference reading. If there is no second reference, press ENT to complete one point offset correction.

Disconnect the Pt 100 simulator and reconnect the Pt 100 wires to solder lugs TP5, TP6 and TP7.

The correct connections according to the wire colours are:

TP5 TP6 TP7 TP8 blue green yellow black

If there is not a Pt 100 simulator available, the adjustment can be made with two resistors of 84 Ω and 154 Ω whose resistance is known precisely. Measure the resistor with a resistance meter. Look up the

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OPERATING MANUAL_______________________________________________________________

++++=

corresponding temperature value from a Pt 100 conversion table or calculate it using the following equation:

D4)]} x R (D3 x R [D2 x R {D1 x R D0 T

(7-1)

where D0 = -243.5673014

D1 = 2.278542701 D2 = 0.002050681 D3 = -6.15025E-06 D4 = 1.34949E-08

Measurement of output currents using test points

If a current output has been connected e.g. to a process computer, the output current cannot be measured at the output connector X2 without disconnecting the external load. The output current can, however, be measured at test points CH1+/CH1- and CH2+/CH2- without disconnecting the output wires. These test points can therefore be used in one point offset correction against an accurate reference or in checking the current output without disconnecting the analogue output from the process.

CH1+

CH1-

CH2+

X15

CH1 +

OPENED COVER OF THE DMP248

FIGURE 7-3 Location of the CH1 and CH2 test points

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CH2

CH2-

CHAPTER 7____________________________________________________________ MAINTENANCE

CH1+

TEST POINTS

FIGURE 7-4 Circuit diagram of the analogue output current test

CH1-

points

Adjusting the contrast of the display

The contrast of the display can be adjusted using the trimmer "LCD display contrast" located next to the press switches.

Vaisala Service Centers

NORTH AMERICAN SERVICE CENTER Vaisala Inc., 100 Commerce Way, Woburn, MA 01801-1068, USA.

Phone: +1 781 933 4500, Fax +1 781 933 8029 Email: us-customersupport@vaisala.com

EUROPEAN SERVICE CENTER Vaisala Instruments Service, Vanha Nurmijärventie 21 FIN-01670 Vantaa,

FINLAND. Phone: +358 9 8949 2758, Fax +358 9 8949 2295 E-mail: instruments.service@vaisala.com

ASIAN SERVICE CENTER Vaisala KK, 42 Kagurazaka 6-Chome, Shinjuku-Ku, Tokyo 162-0825, JAPAN.

Phone: +81 3 3266 9611, Fax +81 3 3266 9610 E-mail: aftersales.asia@vaisala.com

www.vaisala.com

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CHAPTER 8 TECHNICAL DATA

Measured variables

Dewpoint temperature

Measurement range -60...+80 °C (below 0 °C DMP248 outputs frostpoint)

Dewpoint accuracy ± 2 °C (-50...+80 °C) (see figure below)

FIGURE 8-1 Measurement range and accuracy.

Response time (90%) at flow rate 0.08 m/s (1 bar) at 20 °C:

-40 → -20 °C dp 35 s

-20 → -40 °C dp 240 s

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CHAPTER 8____________________________________________________________ TECHNICAL DATA

Temperature

Measurement range -40...+80 °C

for specified Td accuracy 0...+80 °C

Typical accuracy of electronics at +20 °C (+68 °F) ±0.1 °C

Typical temperature dependence of electronics 0.005 °C/°C

Temperature sensor Pt 100 IEC 751 1/3 Class B

Relative humidity

Measurement range 0...100 %RH Accuracy at 20 °C

RH< 10 %RH ± 0.025 %RH + 8.75% of reading RH> 10 %RH ± 0.7 %RH + 2% of reading

Ppm volume concentration (dry)

Typical measurement range 0...5000 ppm Accuracy at 20 °C, 1013.25 mbar 7.3 ppmv + 8.3% of reading

Outputs

Two analogue outputs selectable 0...20 mA 4...20 mA

Typical accuracy of an analogue output at +20 °C ±0.05 % full scale

Typical temperature dependence of an analogue output 0.005 %/°C full scale

Serial outputs RS 232C

0...1 V 0...5 V

0...10 V

RS 485 (option) current loop (option)

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General

Sensor DRYCAPS sensor

Connections screw terminals, 0.5 mm2 wires

(AWG 20), stranded wires recommended

Operating voltage 24 VDC/ isolated VAC

(20...28 V) 115 VAC/230 VAC with power supply module

Power consumption 100 mA maximum (24 VDC) Recommended external load for

current outputs <500 Ω

0...1 V voltage output >2 kΩ (to ground)

0...5 and

0...10 V voltage outputs >10 kΩ (to ground) Operating temperature range

(electronics) -40...+60 °C

with display cover 0...+50 °C

with power supply unit -40...+45 °C Storage temperature range -40...+70 °C Pressure range 0 ...20 bar absolute pressure

Housing material G-AlSi12 (DIN 1725) Housing classification IP 65 (NEMA 4) Bushing for 7...10 mm diameter cable

(8 x 0.5 mm2 shielded cable)

Sensor protection (∅13.5 mm) stainless steel sintered filter

(part no. 16452)

for vacuum applications stainless steel filter

(part no. HM46999 )

Housing dimensions 145 x 120 x 65 mm

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CHAPTER 8____________________________________________________________ TECHNICAL DATA

Sensor head dimensions:

Electronics

PROBE PUSHED DOWN

R1/2 ISO 7/1

178

ø5.5

ø13.5

PROBE UP

cable length 2, 5 or 10 m

adjustment range120 mm

R1/2 ISO 7/1

Weight of display cover 420 g

User interface 3 keys and 4 LEDs inside the

housing or local display keypad (option)

Display (option) 2 x 16 character alphanumeric

character height 3.85 mm (0.15")

Keyboard 1 x 4 keypad

Serial interface modules

Module types RS 485/422

Connections screw terminals for 0.5 mm

Assembly plug-in module Number of devices on line

RS 485/422 32

digital current loop 6 (single loop), 9 (dual loop) Network cable type twisted pair Network line length 1000 m max. Network data speed

RS 485/422 9600 baud max.

digital current loop 4800 baud max.

LCD

digital current loop

wires (AWG 20), stranded wires recommended

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Electromagnetic compatibility

The DMP248 transmitter fulfills the standard EN 61326-1:1997 +Am 1:1998 + Am 2:2001, Electrical equipment for measurement, control and laboratory use - EMC requirements; Industrial environment.

Test methods

Emission

Radiated emissions CISPR16 class B (CISPR22 Class B)

Immunity

Electrostatic discharge (ESD) EN/IEC 61000-4-2 EM field EN/IEC 61000-4-3

Industrial environment: 10 V/m EFT Burst EN/IEC 61000-4-4 Surge EN/IEC 61000-4-5 Conducted RF EN/IEC 61000-4-6

CHAPTER 9 OPTIONS

Power supply 24 VDC (VAC)(standard),

Serial interface RS 232C (standard), RS 485/422,

current loop Cable length 0.56, 2, 5 or 10 metres Alarm output 2 relays 8 A/ 230 V SPCO (Single Pole

Change Over) for adjustable low and

high alarm Display cover cover with or without local display & keypad

115/230 VAC

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CHAPTER 10_______________________________________________ SPARE PARTS AND ACCESSORIES

CHAPTER 10 SPARE PARTS AND

ACCESSORIES

Order code Description

16452SP Sintered filter, stainless steel DRYCAPS

HMP230PW Power supply module 5237 Fuse 160 mA T 5x20 mm for power supply module HMP230RS RS 485/422 serial module HMP230CL Current loop module DMP240ALSP Alarm output unit 17143 Fuse 8 A for alarm output unit DMP248SC Sample cell DMP248BVS Ball valve set DM70 Hand-held Dewpoint Meter DM70

DRYCAP® S dewpoint sensor

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APPENDIX 1 SERIAL COMMANDS__________________________________________________________

APPENDIX 1 SERIAL COMMANDS

APPENDIX 1 79

AUTO-CALIBRATION COMMANDS 81

DRYCAL Defining the frequency of auto-calibration cycles 81 DCAL Forced auto-calibration 82

ANALOGUE OUTPUT COMMANDS 82

AMODE Setting the analogue outputs 82 ASEL Selecting the scaling the analogue output quantities 83 ASCL Scaling the analogue outputs 84

CALIBRATION COMMANDS 85

CRH Relative humidity calibration 85 CT Temperature calibration 85 ACAL Calibrating the analogue outputs 86 L Outputting linear correction coefficients 86 LI Entering linear correction coefficients 87

OUTPUT VIA THE SERIAL BUS 87

R Starting the measurement output 87 S Stopping the measurement output 88 SEND Outputting a reading once 88 DSEND Outputting readings of all connected transmitters once 88 ERRS Outputting error messages 89 ECHO Turning the serial interface echo ON/OFF 89 INTV Setting the output interval for the RUN state 89 FORM Setting the output format 90 FTIME Adding time to output 91 FDATE Adding date to output 92 SERI Serial bus settings 93 UNIT Selecting the output units 93 ADDR Setting the transmitter address 94 RESET Resetting the transmitter 94

OPERATION MODES 95

SMODE Setting the serial interface 95 OPEN & CLOSE 95

OTHERS 96

ITEST Testing the analogue outputs 96 PRES Setting the pressure for pressure compensation and ppm calculations 97 XPRES Setting the pressure for pressure compensation and for ppm calculations temporarily 98 CDATE Entering calibration date 98 DATE Setting the date 98 TIME Setting the time 99 VERS Name and version of the programme 99 ? Outputting the transmitter settings 99 ?? Outputting the transmitter settings also in POLL mode 100 Setting and activating the outputs with menu commands 133 Setting and activating the outputs using an RS line 134

The commands function as described when the serial interface is in full-duplex mode and echo is on. All commands except FORM can be given in either capital or small letters. In the commands <cr> means carriage return, <lf> line feed and <ht> horizontal tabulation.

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APPENDIX 1 SERIAL COMMANDS__________________________________________________________

Auto-calibration commands

DRYCAL Defining the frequency of auto-calibration cycles

DRYCAL<cr>

>drycal DCAL ON Interval min : 60 ? Max dTdp: 2.00 ? dTdp time s : 10 Max corr. : 0.040 ? Settl time s : 50

NOTE

The Max dTdp parameter defines the maximum allowed change of the dewpoint value during the pre-defined dTdp time before autocalibration. If the change in dewpoint value exceeds the limit, the calibration is not started. The auto-calibration is done only after process is stabilized. The dTdp defines the time for Max dTdp measurement.

The Max corr. parameter defines the maximum correction (%RH) the transmitter does during each auto-calibration cycle. The Settl time defines the time the output values (measured before auto-calibration) are frozen after the auto-calibration. The time is for sensor temperature stabilization.

Normally, the Max dTdp and the Max corr. parameters need not be changed.

Auto-calibration takes place only when the security lock jumper is connected.

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APPENDIX 1 SERIAL COMMANDS __________________________________________________________

DCAL Forced auto-calibration

DCAL<cr>

>dcal Calibration... any key to abort > (appears when the auto-calibration

is completed, max. 60 - 70 seconds)

If you press any key, the calibration is interrupted. If no key is pressed, the calibration takes place immediately. The text above is displayed during the calibration. If the process is unstable (see Chapter ) or relative humidity is over 10%, the calibration is not performed. The text above is only shortly displayed and the display returns to the measuring mode. The calibration is not performed again even if the maximum correction is exceeded.

Analogue output commands

AMODE Setting the analogue outputs

Disconnect the security lock jumper!

AMODE a bb.bbb cc.ccc d ee.eee ff.fff <cr>

a = channel 1: U = voltage output

I = current output bb.bbb = lower limit of channel 1 cc.ccc = upper limit of channel 1 d = channel 2: U = voltage output

I = current output ee.eee = lower limit of channel 2 ff.fff = upper limit of channel 2

The bb.bbb, cc.ccc, ee.eee and ff.fff parameters are entered in volts or milliamperes. Sets the analogue outputs on channels 1 and 2. An example of this is when the voltage output on channel 1 is set to be 0...1 V and channel 2 set to 2...10 V:

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APPENDIX 1 SERIAL COMMANDS__________________________________________________________

>AMODE U 0 1 U 2 10 <cr> Ch1 : 0.000 ... 1.000 V Ch2 : 2.000 ... 10.000 V

The current settings can be checked by giving the command without any parameters:

>AMODE <cr> Ch1 : 0.000 ... 20.000 mA Ch2 : 0.000 ... 20.000 mA

ASEL Selecting the scaling the analogue output quantities

Disconnect the security lock jumper!

ASEL xxx yyy <cr>

xxx = channel 1's quantity (Td, ppm, RH, T) yyy = channel 2's quantity (Td, ppm, RH, T)

For example, dewpoint temperature is selected to be output on channel 1 and temperature on channel 2; the temperature range is scaled to 0...60 ° C:

>ASEL Td T <cr> Ch1 ( Td ) lo -50.00 'C ? -40<cr> Ch1 ( Td ) hi 10.00 'C ? 0<cr> Ch2 ( T ) lo 10.00 'C ? 0<cr> Ch2 ( T ) hi 100.00 'C ? 60<cr> >

When the ASEL command is given on its own, the transmitter outputs its current settings:

>ASEL <cr>

Ch1 ( Td ) lo -50.00 'C ? <cr> Ch1 ( Td ) hi 10.00 'C ? <cr> Ch2 ( T ) lo 10.00 'C ? <cr> Ch2 ( T ) hi 100.00 'C ? <cr>

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APPENDIX 1 SERIAL COMMANDS __________________________________________________________

The outputs and their scales can also be given directly with the ASEL command.

ASEL xxx yyy aaa.a bbb.b ccc.c ddd.d <cr>

xxx = channel 1's quantity yyy = channel 2's quantity aaa.a = lower limit of channel 1 bbb.b = upper limit of channel 1 ccc.c = lower limit of channel 2 ddd.d = upper limit of channel 2

ASCL Scaling the analogue outputs

Disconnect the security lock jumper!

ASCL <cr>

Scales the outputs selected on channels 1 and 2. For example, scaling dewpoint temperature on the range of -40...0 °C and temperature 0...+60 °C:

>ASCL <cr> Ch1 ( Td ) lo -50.00 'C ? -40<cr> Ch1 ( Td ) hi 10.00 'C ? 0<cr> Ch2 ( T ) lo 10.00 'C ? 0<cr> Ch2 ( T ) hi 100.00 'C ? 60<cr> >

The output scales can also be given directly with the ASCL command.

ASCL aaa.a bbb.b ccc.c ddd.d <cr>

aaa.a = lower limit of channel 1 bbb.b = upper limit of channel 1 ccc.c = lower limit of channel 2 ddd.d = upper limit of channel 2

For example, when dewpoint temperature is scaled to -40...0 °C on channel 1 and temperature to 0...+60 °C on channel 2:

>ASCL -40 0 0 60 <cr>

Ch1 ( Td ) lo -40.00 'C ? <cr> Ch1 ( Td ) hi 0.00 'C ? <cr> Ch2 ( T ) lo 0.00 'C ? <cr> Ch2 ( T ) hi 60.00 'C ? <cr> >

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Calibration commands

CRH Relative humidity calibration

Disconnect the security lock jumper!

CRH <cr>

With this command the transmitters can be calibrated against two RH references. Two-point calibration is performed using saturated salt solutions in controlled conditions according to the following instructions:

>CRH <cr> RH : 12.00 Ref1 ? 11.3 <cr> Press any key when ready ... RH : 76.00 Ref2 ? 75.5 <cr>

If the stabilization of the sensor to the humidity in the calibrator needs to be monitored, the measurement output can be repeated by giving command c<cr> at Ref1 and Ref2:

>CRH <cr> RH : 12.00 Ref1 ? c <cr> RH : 11.70 Ref1 ? c <cr> RH : 11.50 Ref1 ? 11.3 <cr> Press any key when ready ... RH : 76.00 Ref2 ? 75.5 <cr>

CT Temperature calibration

Disconnect the security lock jumper!

CT <cr>

Using this command the transmitters can be calibrated against an accurate reference, such as a Pt 100 simulator. A two-point calibration is performed as follows:

>CT <cr> T : 0.80 Ref1 ? 0.0 <cr> Press any key when ready ... T : 56.20 Ref2 ? 55.0 <cr>

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In one-point offset correction, the Ref2 prompt is acknowledged with <cr>:

>CT <cr> T : 0.80 Ref1 ? 0.0 <cr> Press any key when ready ... T : 75.50 Ref2 ? <cr>

If the stabilization of the sensor to the temperature of the calibrator or the reference needs to be monitored, the measurement output can be repeated by giving command c<cr> at Ref1 and Ref2:

>CT <cr> T : 0.80 Ref1 ? c <cr> T : 0.40 Ref1 ? 0.00 <cr> Press any key when ready ... T : 56.20 Ref2 ? 55.0 <cr>

ACAL Calibrating the analogue outputs

Disconnect the security lock jumper!

ACAL <cr>

Calibrates the outputs selected on channels 1 and 2. The output is measured and the measured values (mA or V) entered as calibration coefficients. For example, calibrating the outputs when 0...10 V signal has been selected on both channels (set with AMODE command)

>ACAL <cr> Ch1 U1 (V ) ? 0.123 <cr> Ch1 U2 (V ) ? 9.98 <cr> Ch2 U1 (V ) ? 0.120 <cr> Ch2 U2 (V ) ? 9.98 <cr>

L Outputting linear correction coefficients

L <cr>

Calibration coefficients can be checked with command L.

>L <cr> RH offset : 0.000 RH gain : 1.000 Ts offset : 0.000 Ts gain : 1.000

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LI Entering linear correction coefficients

Disconnect the security lock jumper!

LI <cr>

The LI command is one way of calibrating the transmitters.

>LI <cr> RH offset : 0.000 ? -.6 <cr> RH gain : 1.000 ? <cr> Ts offset : 0.000 ? <cr> Ts gain : 1.000 ? .4 <cr>

The factory settings are offset 0 and gain 1.

NOTE

The temperature unit in offset correction is always degrees Centigrade, even if the transmitter is using non-metric units (Fahrenheit) in its measurement output.

Output via the serial bus

R Starting the measurement output

R <cr>

Starts output of measurements to the peripheral devices (PC display or printer); output interval is set with command INTV.

Factory setting of the output format:

Td= -9.3 'C PPM= 2733 T= 22.1 'C RH= 10.4 %RH Td= -9.3 'C PPM= 2730 T= 22.1 'C RH= 10.4 %RH

...

When the transmitter sends out the readings, the serial interface does not echo any commands; the only command that can be used is S (stop). The output format can be changed with command FORM.

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S Stopping the measurement output

S<cr>

Ends the RUN state; after this command all other commands can be used.

SEND Outputting a reading once

SEND <cr> in STOP state

SEND aa <cr> in POLL state

aa = address of the transmitter when more than one transmitter is

connected to a serial bus (0...99; set with command ADDR)

Outputs the current measurement readings via the serial line. The output type is the following:

Td= -9.3 'C PPM= 2733 T= 22.1 'C RH= 10.4 %RH Td= -9.3 'C PPM= 2730 T= 22.1 'C RH= 10.4 %RH

...

The output format can be changed with command FORM.

DSEND Outputting readings of all connected transmitters once

DSEND <cr>

All transmitters connected to the serial bus send their addresses and current measurement readings in an order defined by their addresses. After receiving DSEND command a transmitter sets a delay time according to its address value and sends the data after this delay. DSEND works also in POLL mode. With this command, the user can for example easily find out the addresses of the transmitters. The output when four transmitters with addresses 4, 5, 10, 33 have been connected to the serial bus:

>dsend <cr> 4 14.43 %RH 5 22.7 'C 10 14.99 %RH 33 22.3 'C >

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ERRS Outputting error messages

ERRS <cr>

During operation error messages are not output automatically through the serial interface. If there is any reason to doubt that there is something wrong with the transmitter, possible error messages can be output with command ERRS.

If there are no error messages, only a prompt is displayed:

>ERRS <cr> >

If errors have occurred, the transmitter outputs the error code (see Appendix 5 for error messages):

>ERRS <cr> E40 f ( all ) out of range >

ECHO Turning the serial interface echo ON/OFF

ECHO xxx <cr>

xxx = ON or OFF

When the echo is off, the commands given through the serial interface or the prompt > cannot be seen on the display. When the serial interface is in half-duplex mode, the echo is always off. Even then the ECHO command can indicate that echo is on.

INTV Setting the output interval for the RUN state

INTV xxx yyy <cr>

xxx = output interval (0...255)

0: no pause between outputs

yyy = unit (s, min or h)

Sets the output interval when the transmitter outputs measurement readings to a peripheral device. For example, the currently valid settings are output with:

>INTV <cr> Output intrv. : 0 min

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When this is changed into 10 minutes, the command is:

>INTV 10 <cr> Output intrv. : 10 min

The unit is changed into seconds with:

>INTV S <cr> Output intrv. : 10 s

The change can also be done with one command:

>INTV 10 S <cr> Output intrv. : 10 s

FORM Setting the output format

FORM <cr>

"xxx...xxx"

? zzz...zzz <cr>

NOTE

xxx...xxx = old format zzz...zzz = new format

The FORM command sets the format of the outputs generated in RUN state and by SEND command.

Please note that capital and small letters have different meanings.

\DD..DD\ dewpoint temperature \TT..TT\ temperature \UU..UU\ relative humidity \MM..MM\ ppm concentration \PP..PP\ absolute pressure (hPa) (manually feeded value) \uu..uu\ unit according to the preceding variable \n line feed <lf> \r carriage return <cr> \t horizontal tabulation <ht> or <tab> \\ \

For example:

format output \UUU.UU\ \+TT.TT\\r 100.00 +99.99 <cr> \TTT.T\ \uu\\r\n 15.2 'C <cr><lf> \UUU.U\ \uuu\\+DD.D\ \uu\\r 46.9 %RH +10.8 'C <cr>

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Any text can be written in the command and it appears in the output. For example:

RH: \UUU.U\ T: \+TT.TT\\r RH: 54.0 T: +25 <cr>

The format can be deleted by giving \ as a parameter:

>FORM \<cr> Note. only one space before \ and none after

>FORM <cr> "xxx...xxx" ?\<cr>

An example of a format suitable for use in Microsoft Excel spreadsheets:

>FORM <cr> "xxx...xxx" ?\UUU.U\\t\TTT.T\\t\DDD.D\\t\\r\n <cr>

The output is then:

47.4<tab> 22.4 <tab> 10.6 <tab> <cr><lf>

FTIME Adding time to output

FTIME xxx <cr>

xxx = ON or OFF

When FTIME is activated, the current time is output at the beginning of the output line. The time is set with command TIME. After RESET or power on the current time is 00:00:00. Activating the time output

>ftime on Form. time : ON >intv 5 s setting the output interval Output intrv. : 5 s >r 09:31:13 RH= 19.4 %RH T= 26.0 'C 09:31:18 RH= 19.4 %RH T= 26.0 'C 09:31:23 RH= 19.8 %RH T= 26.0 'C 09:31:28 RH= 19.6 %RH T= 26.0 'C 09:31:33 RH= 19.5 %RH T= 26.0 'C 09:31:38 RH= 19.5 %RH T= 26.0 'C ...

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APPENDIX 1 SERIAL COMMANDS __________________________________________________________

Inactivating the time output

>ftime off Form. time : OFF >r RH= 19.4 %RH T= 26.1 'C RH= 19.8 %RH T= 26.1 'C RH= 20.6 %RH T= 26.1 'C RH= 20.5 %RH T= 26.1 'C RH= 19.9 %RH T= 26.1 'C RH= 19.6 %RH T= 26.1 'C ...

FDATE Adding date to output

FDATE xxx <cr>

xxx = ON or OFF

When FDATE is activated, the current date is output at the beginning of the output line. The date is set with command DATE. After RESET or power on the current date is 1991-01-01. Activating the date output

>fdate on Form. date : ON >r 1995-03-10 RH= 21.1 %RH T= 26.0 'C 1995-03-10 RH= 21.3 %RH T= 26.0 'C 1995-03-10 RH= 23.1 %RH T= 26.0 'C 1995-03-10 RH= 22.2 %RH T= 26.0 'C 1995-03-10 RH= 20.6 %RH T= 26.0 'C ...

Inactivating the date output

>fdate off Form. date : OFF >r RH= 20.2 %RH T= 26.0 'C RH= 19.9 %RH T= 26.0 'C RH= 19.8 %RH T= 26.0 'C RH= 19.7 %RH T= 26.0 'C RH= 19.7 %RH T= 26.0 'C ...

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SERI Serial bus settings

SERI b p d s x <cr>

b = bauds (300, 600, 1200, 2400, 4800, 9600) p = parity (n = none, e = even, o = odd) d = data bits (7 or 8) s = stop bits (1 or 2) x = duplex (H = half, F = full)

Giving the command on its own outputs the current settings:

>SERI <cr> 4800 E 7 1 FDX

The settings can be changed one parameter at a time or all parameters at once:

>SERI O H <cr> changing parity and duplex 4800 O 7 1 HDX

>SERI 600 N 8 1 F <cr> changing all parameters 600 N 8 1 FDX

The processor does not allow the following combinations:

• no parity, 7 data bits, 1 stop bit: if this combination is given the DMP248

programme will change the number of stop bits to 2

• even or odd parity, 8 data bits, 2 stop bits: if this combination is given the

programme changes the number of stop bits to 1

NOTE

The serial bus settings become effective only after reset.

When the half-duplex mode is set, it will automatically turn the echo off. Even then the ECHO command can indicate that echo is on.

UNIT Selecting the output units

UNIT x <cr>

x = m(etric units)

n(on-metric units)

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APPENDIX 1 SERIAL COMMANDS __________________________________________________________

metric units non-metric units Td °C °F T

°C °F RH %RH %RH

For example, the command for setting the non-metric units is:

>UNIT N <cr> Output units : non metric

When the command is given with no parameters, the transmitter outputs the currently valid setting.

ADDR Setting the transmitter address

ADDR aa <cr>

aa = address (0...99)

The address is used when more than one transmitter is connected to one serial bus. The ADDR command makes it possible to communicate with one transmitter at a time in POLL state.

For example, transmitter is given address 99

>ADDR <cr> Address : 2 ? 99 <cr>

When asking the current address, no address number is given:

>ADDR <cr> Address : 2 ? <cr>

RESET Resetting the transmitter

RESET <cr>

Resets the transmitter. All settings that have been changed stay in the memory even after reset or power failure.

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Operation modes

SMODE Setting the serial interface

SMODE xxxx<cr>

xxxx = STOP, RUN or POLL

In STOP mode: measurements output only by command, all commands can

be used In RUN mode: outputting automatically, only command S can be used In POLL mode: measurements output only with command SEND. When in

POLL mode, the output state is changed as follows:

OPEN aa <cr>

SMODE xxxx<cr>

aa = address of the transmitter xxxx = STOP, RUN or POLL

The OPEN command sets the bus temporarily in STOP MODE so that the SMODE command can be given. For example:

OPEN & CLOSE

nn = address of the transmitter (0...99)

In STOP mode: command OPEN has no effect, CLOSE sets the transmitter in

In POLL mode: command OPEN sets the transmitter temporarily in STOP

When more than one transmitter is connected to the same serial bus, the POLL mode makes it possible to communicate with the transmitters. For example, a relative humidity calibration is performed at transmitter 2 (<bel> = ASCII 7):

>SMODE <cr> which mode is in use at the moment Serial mode : STOP >SMODE STOP <cr> setting STOP mode Serial mode : STOP

OPEN nn <cr>

CLOSE <cr>

POLL mode

mode, command CLOSE returns the instrument to POLL

mode

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APPENDIX 1 SERIAL COMMANDS __________________________________________________________

>OPEN 2 <cr> <cr><lf> 'DMP nn line opened for operator commands' <cr><lf><lf><bel> >CRH <cr> ... >CLOSE <cr> <cr><lf> 'line closed' <cr><lf>

Others

ITEST Testing the analogue outputs

ITEST <cr>

ITEST a b <cr>

a = current/voltage of channel 1 b = current/voltage of channel 2

The operation of the analogue outputs can be tested by forcing the outputs to given values which can then be measured with a current/voltage meter from the analogue outputs. The response to ITEST command gives six outputs/parameters. Only the first two are relevant; they show the channel current or voltage in mA or V. The other four figures contain information for service purposes only. Examples:

• reading the channel outputs and parameters

>itest <cr>

1.9438 2.3483 1.00694 10.64634 1.97374 2.17665 >

• forcing outputs 0.5 V and 4 V to channels 1 and 2

>itest 0.5 4 <cr>

0.5000 4.0000 1.00694 10.62970 1.23336 3.01722 >

• releasing the forced control and reading the outputs

>itest <cr>

1.9427 2.3392 1.00731 10.62428 1.97157 2.16978 >

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Vaisala DMP248 OPERATING MANUAL

Specifications and Main Features

Frequently Asked Questions

User Manual