Vaisala DMP248 User manual

DMP248 Dewpoint
Transmitter
OPERATING
MANUAL
M210492EN-A
JULY 2003
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PUBLISHED BY
Vaisala Oyj Phone (int.): ([phone]
P.O. Box 26 Fax: [phone]
FIN-00421 Helsinki
Finland
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 2003
No part of this manual may be reproduced in any form or by any
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.
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_________________________________________________________________________CONTENTS
VAISALA __________________________________________________________________________ I
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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OPERATING MANUAL_______________________________________________________________
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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
VAISALA __________________________________________________________________________1
CHAPTER 1GENERAL INFORMATION
Safety
Throughout the manual important instructions regarding the safety
considerations are focused as follows.
WARNING 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 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 Note highlights important information. It calls attention to an essential
procedure, practice, condition or the like.
Warranty
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.
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CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION
VAISALA __________________________________________________________________________3
CHAPTER 2PRODUCT 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 se-
lected 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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OPERATING MANUAL_______________________________________________________________
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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
Pw
Pws T
out = + 0*( ) (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
VAISALA __________________________________________________________________________5
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.
30°C
20°C
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
00.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045
1/Pws(T)
RHout(%)
FIGURE 2-1Device output during hypothetical offset calibration
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 RH0as 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_______________________________________________________________
6______________________________________________________________________M210492EN-A
FIGURE 2-2The DRYCAPsensor mounted on a DMP248 probe.
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.
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CHAPTER 3_______________________________________________________________INSTALLATION
VAISALA __________________________________________________________________________7
CHAPTER 3INSTALLATION
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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8 _____________________________________________________________________M210492EN-A
ø6.5
CL ENT
133
145
104 120
65
FIGURE 3-1 Dimensions of the DMP248 electronics housing (in
mm).
NOTE 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.
PROBE UP
PROBE
PUSHED
DOWN
cable length
2, 5 or 10 m
ø5.5
178
31
ø13.5
adjustment
range120 mm
29
R1/2 ISO 7/1
non leaking screw (A)
(factory setting)
or leak screw (B)
(included in the package)
149
clasp nut
fitting body
FIGURE 3-2 Probe dimensions (in mm).
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CHAPTER 3_______________________________________________________________INSTALLATION
VAISALA __________________________________________________________________________9
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
>10.5mm
fitting body
hex=24mm
tapered thread
R1/2ISO7/1ø19mm drilling
sealing with:
1.LOCTITE®No542 +activ.No7649 (t=-55...+150 °C)
2.MEGA-PIPE EXTRANo7188 (t=-55...+170 °C)
3.PTFEtape (t=-60...+210 °C)NOTE:the tape doesnotlock
the partstogether.Therefore,usetwoforkspanners(hex24 and
27 mm)fortightening and opening the claspnutofthe probe
parallel thread
G1/2 ISO 228/1
(BS 2779, JIS B0202)
>40mm
Process or pipe wall
FIGURE 3-3Sealing 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).
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).
60°
probe
fitting body
clasp nut
max.
a pen
FIGURE 3-4Tightening the clasp nut.
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OPERATING MANUAL_______________________________________________________________
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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 by-
pass 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).
recommended adjustment range
25...135 mm
non leaking screw
(screw A, factory setting)
welded sleeve (G1/2, Ø 40 mm)
process wall
Leave at least 25 mm (1 ")
of probe head free to enable
a faster response time in
unpressurized processes
25 mm
FIGURE 3-5Installing the probe in an atmospheric process.
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
VAISALA _________________________________________________________________________11
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.
process pipe
welded sleeve
(G1/2)
Non leaking screw
(screwA)
closing valve
(ball valve)
sealing
capped nut
DIN917-M22x1.5
when the probe ispulled
outformaintenance,cap
the holewithacapped nut;
thisway,the process can be
open although the probe is
notinplace
FIGURE 3-6Installing the sensor head directly on the process pipe.
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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OPERATING MANUAL_______________________________________________________________
12_____________________________________________________________________M210492EN-A
handle
probe
non-leaking
screwA
process pipe /chamber
ball ofthe ball
valve
(holediameter
atleast14 mm)
>30 mm
FIGURE 3-7Installing the sensor head through the DMP248BVS
ball valve assembly.
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 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
VAISALA _________________________________________________________________________13
•STEP 1: mount the probe with the ball valve assembly closed;
tighten the clasp nut manually.
fitting body
R1/2cone,sealed
bushing
R1/2cone
sealed
bushing R1/2cone/G1/2(40 bar)
e.g.Camozzi2520-1/2-1/2
ball valve1/2"(40 bar)
e.g.AtlasCopco:BAL-1A15 (G1/2)
nipple
R1/2cone
sealed
(the bushing serves for
moving the probe (sinter)
to such a distance from the
ball valve that the valve
can be closed)
>30 mm
clasp nut
FIGURE 3-8Installing the probe through the ball valve assembly;
step 1.
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OPERATING MANUAL_______________________________________________________________
14_____________________________________________________________________M210492EN-A
•STEP 2: open the ball valve assembly.
R1/2ISO7/1
120mm
ø5.5
61
(40)
148 mm
manual
press
tool
probe pipe
fitting
ferrule
marking groove
leakscrew(B)
(hex.1.5mm)
ø14
29
15
ø13.5
DRYCAP®sensor
filter
fitting body
(hex.24 mm)
handle
adjustmentrange
ball ofthe
ball valve
claspnut
(hex27 mm)
> 14
=
O-ring
FIGURE 3-9Installing the probe through the ball valve assembly;
step 2 (measures in mm).
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CHAPTER 3_______________________________________________________________INSTALLATION
VAISALA _________________________________________________________________________15
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.
VALVE OPEN
MANUAL
PRESS TOOL
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.
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OPERATING MANUAL _______________________________________________________________
16 ____________________________________________________________________M210492EN-A
NOTE
keep the marking
groove in sight when
using leak screw (B)
gas escape channel:
use this position for
by-pass measurements
leak screw (B)
DRYCAP® sensor
sintered
filter
process pipe
or chamber
O-ring
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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