Vaisala HMP228 User Manual

HMP228

Moisture and Temperature

Transmitter for Oil

USER'S GUIDE

M210282en-A May 2002

PUBLISHED BY Vaisala Oyj Phone : (+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.

HMP228

M210282en-A Operating Manual

Contents

1. PRODUCT DESCRIPTION...................................................................................................1

1.1 General characteristics........................................................................................... 1

1.2 Typical applications................................................................................................1

1.2.1 About the method used for measuring moisture in oil................................1

1.2.2 Lubrication oil in paper machines..............................................................2

1.2.3 Transformer oil ......................................................................................... 2

2. INSTALLATION ................................................................................................................... 3

2.1 Selecting the place of installation for the probe and the transmitter................... 3

2.2 Mounting..................................................................................................................4

2.2.3 Installing the probe through the ball valve assembly.................................. 6

2.2.4 Mounting the probe directly in the process pipe ......................................... 9

2.3 Signal cabling and grounding .............................................................................. 10

2.3.1 Electrical connections ............................................................................. 10

2.3.2 Connection to an AC supply.................................................................... 11

2.3.3 Grounding...............................................................................................12

3. COMMISSIONING.............................................................................................................. 14

3.1 Changing the parameters ..................................................................................... 14

3.1.1 Security lock jumper................................................................................ 14

3.1.2 Commands and security lock jumper....................................................... 15

3.2 Using the RS 232C serial bus............................................................................... 16

3.3 Using LED commands........................................................................................... 18

3.4 Using display/keypad commands......................................................................... 18

3.4.1 Display mode.......................................................................................... 18

3.4.2 Command mode ..................................................................................... 19

3.4.3 Entering numbers.................................................................................... 19

4. MAINTENANCE ................................................................................................................. 20

4.1 Self-diagnostics ....................................................................................................20

4.2 Reference measurements..................................................................................... 20

4.3 Moisture calibration.............................................................................................. 21

4.3.1 Two point calibration procedure ............................................................... 22

4.3.1.1 Using serial commands............................................................................22

4.3.1.2 Using display/keypad commands ............................................................. 22

4.3.1.3 Using LED commands.............................................................................. 23

4.3.2 One point calibration procedure ............................................................... 23

4.3.2.1 Using serial commands............................................................................23

4.3.2.2 Using display/keypad commands ............................................................. 24

4.3.2.3 Using LED commands.............................................................................. 24

4.4 Changing the moisture sensor.............................................................................24

4.4.1 Calibration procedure after sensor change...............................................25

4.4.1.1 Using serial commands............................................................................25

4.4.1.2 Using display/keypad commands ............................................................. 25

4.4.1.3 Using LED commands.............................................................................. 26

4.4.5 Humidity calibration table......................................................................... 27

4.6 Temperature calibration........................................................................................ 27

4.6.1 One point offset correction.......................................................................27

4.6.1.1 Using serial commands............................................................................27

iii

HMP228 Operating Manual M210282en-A

4.6.1.2 Using display/keypad commands..............................................................28

4.6.1.3 Using LED commands.............................................................................. 28

4.6.2 Two point temperature calibration.............................................................28

4.6.2.1 Using serial commands ............................................................................ 28

4.6.2.2 Using display/keypad commands..............................................................29

4.6.2.3 Using LED commands.............................................................................. 29

4.6.3 Temperature channel adjustment with Pt 100 simulators..........................30

4.7 Analogue output channels....................................................................................31

4.7.1 Setting the analogue outputs ....................................................................31

4.7.1.1 Using serial output....................................................................................32

4.7.1.2 Using display/keypad commands..............................................................33

4.7.2 Selecting and scaling the analogue output quantities................................34

4.7.2.1 Using serial output....................................................................................34

4.7.2.2 Using display/keypad commands..............................................................34

4.8 Checking and calibrating the analogue outputs..................................................35

4.8.1 Measurement of output currents using test points .....................................35

4.8.1 Calibration of the analogue outputs ..........................................................36

4.8.1.1 Using serial commands ............................................................................ 37

4.8.1.2 Using display/keypad commands..............................................................37

4.8.1.3 Using LED commands.............................................................................. 38

4.9 Other functions......................................................................................................38

4.9.1 Adjusting the contrast of the display.........................................................38

4.9.2 Reverting to factory settings of the serial port.......................................... 38

5. TECHNICAL DATA.............................................................................................................40

5.1 Water activity.........................................................................................................40

5.2 Temperature...........................................................................................................40

5.4 Analogue outputs..................................................................................................40

5.5 Electronics.............................................................................................................41

5.6 Mechanics..............................................................................................................41

5.7 Electromagnetic compatibility.............................................................................. 43

5.7.1 Emissions................................................................................................43

5.7.2 Immunity .................................................................................................43

6. OPTIONS ...........................................................................................................................44

7. SPARE PARTS ...................................................................................................................44

APPENDIX 1: SERIAL COMMANDS..........................................................................................45

APPENDIX 2: DISPLAY COMMANDS........................................................................................66

APPENDIX 3: POWER SUPPLY MODULE ................................................................................ 73

APPENDIX 4: INSTALLING AND USING THE RS 485/422 SERIAL PORT MODULE ................77

APPENDIX 5: INSTALLING AND USING THE DIGITAL CURRENT LOOP MODULE ................88

APPENDIX 6: ERROR MESSAGES ...........................................................................................98

APPENDIX 8: CONNECTORS..................................................................................................105

APPENDIX 9: WIRING 109

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HMP228

M210282en-A Operating Manual

1. PRODUCT DESCRIPTION

1.1 General characteristics

The HMP228 transmitter is a microprocessor based instrument for the measurement of moisture in terms of water activity e.g. in the lubrication of circulation systems or in transformer oil. The transmitter incorporates a capacitive thin film sensor. The operation of the sensor is based on changes in its capacitance as the thin polymer film absorbs water molecules.

The HMP228 transmitter has two analogue outputs and can be connected to a serial bus via the RS 232C interface or 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. Two analogue output signals can be scaled and the measurement ranges changed within certain limits. The HMP228 transmitter can be supplied with two, five or ten metre sensor head cable.

The HMP228 also provides for accurate temperature measurement. It is an easy-to-install on-line transmitter which can be calibrated against traceable salt solutions.

Options Power supply 24 VDC (standard); (24 VAC: see Chapter 2.3.2),

Serial interface RS 232C (standard), RS 485/422, current loop Display cover cover with or without local display & keypad Alarm output unit not with 115/230 VAC power supply Cable length 2, 5 or 10 metres Cable connectors for 24 VDC supply, for analogue outputs, for RS

1.2 Typical applications

1.2.1 About the method used for measuring moisture in oil

The HMP228 transmitter measures water in oil in terms of water activity (aw) which can be determined as follows: water activity indicates the amount of oil in the scale of 0 - 1 aw. In this scale, 0 aw is an indication of completely water free oil and 1 aw an indication of oil fully saturated with water. Water is present in free form.

115/230 VAC

232C line and for RS 485 single loop line; see Appendix 8 for details.

The most important feature which distinguishes the measurement of water activity (aw) from the traditional measurement of absolute water content (in

HMP228 Operating Manual M210282en-A

ppm) is that the saturation point remains stable regardless of the oil type or the aging of oil, additives used etc. As water activity exceeds 0.9 aw in any system, there is a risk for segregation (especially if the temperature decreases). The water activity is used for alarming at the point of >0.9 aw that the risk for free water in the system is obvious. The most important advantages of this system are the fact that water activity is immune to the aging of oil and to additives, and that the HMP228 transmitter can be used for continuous on-line measurements. In addition, the HMP228 can be calibrated against salt solutions and no reference oils are needed.

1.2.2 Lubrication oil in paper machines

Typically, a paper machine contains two or three separate lubrication systems. Usually, one is located at the wet end and the other at the dry end. There is a certain amount of free moisture constantly present which means that there is a risk of this moisture becoming into contact with the machine bearings. The most common reasons for the entrance of water are an inadequate sealing of the housing and cleaning with high pressure. However, accidental leakages from oil coolers and other equipment may also cause damage. In paper machines, the oil should absorb water while lubricating the bearings and then release this water when collected into the reservoir. It is to be noted that bearings should never be exposed to oils that have a high water content; this is especially important during standstill because the risk for corrosion process increases as the oil temperature decreases. It is essential to monitor the water content and keep it on a suitable level.

When measuring the water content of oil in paper machines, it would be useful to measure the water activity before an oil reservoir and from a pressure line flow. This way, the performance of dehumidifiers can be kept under control to ensure that no free water reaches the bearings.

1.2.3 Transformer oil

The determination of moisture in oil is an essential part of a comprehensive transformer maintenance program. Aging and deterioration increase the capacity of oil to absorb water. The primary interest in transformers is to measure the water not in oil but in the cellulosic insulation around the transformer windings. Heating and cooling have a considerable effect on moisture levels in oil. While temperature raises, the paper insulation of transformers tends to loose moisture which is absorbed by the oil surrounding it. Saturation level is thus a true indicator of moisture present. The HMP228 method provides for a reliable detection of the aging of oil and possible leakages. Water activity helps to prevent heavy overloadings and to monitor the transportation of moisture in the transformer.

HMP228

M210282en-A Operating Manual

2. INSTALLATION

2.1 Selecting the place of installation for the probe and the transmitter

Select a place which gives a true picture of the process. Oil should circulate freely around the sensor; a rapid oil flow is recommended. Install the sensor directly into the circulation system and not into the oil reservoir because of deposition.

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 pipe 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.

NOTE

Avoid mounting the transmitter housing close to steam sources or directly exposed to rain. To ensure an IP 65 class protection:

1. Always mount the transmitter housing with the cable bushings pointing downwards.

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.

NOTE

Take care not to damage the pipe of the probe. If the pipe is damaged, the probe head is less tight and will not go through the clasp nut. Make sure that the filter is tightly fastened to protect the sensors.

HMP228 Operating Manual M210282en-A

2.2 Mounting

In Figures 2.2.1 and 2.2.2 you can see the dimensions of the HMP228 transmitter and probe:

104

ENT

120

ø6.5

133

145

Figure 2.2.1 Dimensions of the HMP228 electronics housing (in mm)

Probe pushed down

Probe up

Parallel thread

Tapered thread

180 / 400

216 / 435

Ø13.5

Ø12

A:Probe 180mm adjustment range 120mm

Probe 400mm adjustment range 340mm

Figure 2.2.2 Probe dimensions (in mm).

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M210282en-A Operating Manual

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

>10.5mm

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

Process or pipe wall

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

ø19mm drilling

>40mm

Figure 2.2.3 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 2.2.4). Note that the minimum recommended distance of the fitting body and the probe head is 40 mm (see Figure 2.2.3).

Adjust the probe to a suitable distance according to the type of installation and tighten the clasp nut first manually; mark the fitting body and the clasp nut and tighten the clasp nut a further 50 - 60 ° with a fork spanner (see Figure

2.2.4). Pushing the probe head through the ball valve assembly. Open and close the

ball valve assembly with the marking groove always in sight. When the probe has been pressed through, the nut is tightened 50 - 60 ° with a fork spanner (hexacon 27 mm).

probe

a pen

fitting body

clasp nut

60°

max.

Figure 2.2.4 Tightening the clasp nut

NOTE

Be careful not to tighten the clasp nut more than 60° as this may result in difficulties when trying to pull the probe head up.

HMP228 Operating Manual M210282en-A

2.2.3 Installing the probe through the ball valve assembly

It is recommended that the sensor head is installed in the process through the ball valve assembly. Use a 1/2" ball valve assembly with a hole diameter of 14 mm or more. With this 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 2.2.3.1. for detailed instructions.

probe

handle

>30 mm

ball of the ball valve (hole diameter > 14 mm)

process pipe / chamber

Figure 2.2.3.1 Installing the sensor head through the 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 for installing or removing the probe. However, if the process is shut down before removing the probe, the process pressure can be max. 20 bars.

HMP228

bushing R1/2 cone/ G1/2 (40 bar) e.g. Camozzi 2520-1/2-1/2 (the bushing serves for moving the probe (sinter) so such a distance from the ball valve that the valve can be closed)

NOTE tighten the clasp nut manually

fitting body R1/2 cone, sealed

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

bushing R1/2 cone, sealed

nipple R1/2 cone, sealed

> 30 mm

welded nipple diam. 21.3 x S material: steel or AISI 304L

the nipple edges have to be rounded

Operating Manual

See Figures 2.2.3.2 - 2.2.3.4 for detailed description of installation through the ball valve assembly. 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.

• STEP I: mount the probe with the ball valve assembly closed

Figure 2.2.3.2 Installing the probe through the ball valve

assembly; step 1

HMP228

R1/2 ISO 7/1

53.6

ø5.5

adjustment range 120mm

148

ø14

(40)

>ø14

ø12

~8.5

~22.5

sintered filter

moisture sensor

O-ring

wedge ring

nut (AV=27mm)

screw A

process pipe or chamber

Operating Manual

• STEP 2: open the ball valve assembly

Figure 2.2.3.3 Installing the probe through the ball valve

assembly; step 2 (measures in mm)

The clasp nut is tightened manually prior to opening the ball valve assembly.

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M210282en-A Operating Manual

• STEP 3: push the probe head through the ball valve assembly into the

process. 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 2.2.3.4 Installing the probe through the ball valve

assembly: step 3

2.2.4 Mounting the probe directly in the process pipe

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

HMP228

CH1- and CH2- are connected

DO NOT USE POWER SUPPLY

Power supply

Operating Manual M210282en-A

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

welded sleeve (G1/2) or tube with thick walls

capped nut DIN 917-M22x1.5

sealing

probe

closing valve (ball valve)

Figure 2.2.4 Installing the sensor head directly in a process pipe

2.3 Signal cabling and grounding

2.3.1 Electrical connections

Ch1

Current loop or RS485 module

Sensor connections

GND

Figure 2.3.1 Electrical connections

Ch2

24V

+ Ch1 -

V mA

+ 24V -

+ Ch2 -

V mA

together internally (X2).

GROUND (-) AS OUTPUT SIGNAL GROUND (X1)!

HMP228

common

M210282en-A Operating Manual

Power supply 24 VDC

24 VAC (see Chapter 2.3.2) with power supply module 115/230 VAC 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.

See Appendix 3 on how to connect the power supply module to the transmitter.

2.3.2 Connection to an AC supply

The HMP228 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 short-circuit. To avoid this, always use separate floating supply for each transmitter (see Figure 2.3.2 A). However, if several transmitters have to share one transformer, the phase (∼) must always be connected to + connector in each transmitter (see Figure 2.3.2 B).

A) NO COMMON LOOP FORMED - RECOMMENDED

HMP228 transmitter Controller

24 VAC

HMP228 transmitter

B) COMMON LOOP FORMED -

HMP228 transmitter

signal

supply

NOT RECOMMENDED!

o utput

voltage

signal

output

voltage

Controller

24 VAC

HMP228 transmitter

signal

supply

output

voltage

shared line

voltage

signal

o utp ut

Figure 2.3.2 Connecting the transmitter to an AC supply

HMP228 Operating Manual M210282en-A

2.3.3 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

• insert the wires into the transmitter housing through the gland

• tighten the nut

HMP228

M210282en-A Operating Manual

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

around the wires

Use connectors instead of traditional cabling. See Appendix 8 for connector types available and for detailed instructions.

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.

When mains power supply is used, ground the housing with a protective ground wire using a grounding screw on the right side of the power supply module (see Appendix 3 for details).

HMP228 Operating Manual M210282en-A

3. COMMISSIONING

When the HMP228 transmitter leaves the factory, its measurement ranges and output signals have already been scaled according to the order form completed by the customer. The unit is calibrated at the factory and ready to operate when the power is turned on. If you take into use active current, voltage or serial bus outputs, make these connections first; appendix 9 describes them in detail.

NOTE

Make sure that the power is not turned on until cables have been connected to screw terminals!

In transmitters with display, the software version appears for a few seconds when the power is turned on. After this, measurement results appear automatically. Should an error message appear on the display, consult Appendix 6.

If your transmitter has a blank cover and the LED indicator inside the housing lights up, consult Appendix 6 for further information.

Appendix 7 contains information on how to determine the ranges for alarm outputs and alarm controls when an alarm output unit is used, and Appendix 8 describes the use of connectors.

3.1 Changing the parameters

If necessary, the user can subsequently change the measurement units between metric and non-metric and select and scale the output signals with software functions. This is done through commands, either utilizing the menus on the local display or giving commands through the serial interface (see Appendices). 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, enter) inside the transmitter housing. There are four LEDs to indicate the commands given with the up and down switches. All HMP228 units incorporate these switches and LED indicators. LED commands can be used to calibrate the transmitters (both humidity and temperature) or to calibrate the analogue outputs.

If you need to change some functions, read the following chapters carefully.

3.1.1 Security lock jumper

Before the settings can be changed, the user must first remove the security lock jumper in connector X15 (see Figure 3.1.1). The security lock jumper

HMP228

M210282en-A Operating Manual

makes it impossible to change the transmitter settings by mistake. The jumper should be removed only for changing the settings and for calibration.

X15

Change of settings disabled

Current loop or RS485 module

Sensor connections

Ch1

Rx GND Tx

Ch2

24V

Figure 3.1.1 Location of the security lock jumper

When the security lock jumper is connected, some commands cannot be used, see Chapter 4.

If you wish to take into use variables that are not included in the configuration of your transmitter, contact Vaisala for more information.

3.1.2 Commands and security lock jumper

In order to prevent any tampering with the transmitter settings, the transmitters 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:

• serial commands: CRH, CT, FCRH, ACAL; AMODE, ASEL, ASCL

• all LED commands

• display/keypad commands:

Cali ð RH T

Analog outputs

Mode ð Analog outputs ð Mode

Scale

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

Disconnect the security lock jumper!

HMP228

GND

HMP228

Operating Manual M210282en-A

3.2 Using the RS 232C serial bus

Rx GND Tx

X17

Tx Nc

Current loop or RS485 module

Ch1

Rx GND Tx

Sensor connections

Ch2

24V

Figure 3.2.1 Serial bus connections

To connect a PC to the HMP228 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

TERMINAL

D9S

D25S

D25P

2 5 3

4 6 7 8

3 7 2

5 6 8

3 7 2

Figure 3.2.2 Connection of cables

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. 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

HMP228

M210282en-A Operating Manual

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

HMP228 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 an 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.

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 HMP228. It is always preferable to use the connector X16 instead of the connector X17 because it is more immune to interferences.

The serial commands are described in Appendix 1.

HMP228 Operating Manual M210282en-A

3.3 Using LED commands

NOTE

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

LED commands can be used to operate the transmitters in the field. These commands can be used in humidity and temperature calibration and calibration of the analogue outputs.

Open the housing and press any one of the three press switches. The LEDs will light up for 2...3 seconds.

LEDS

PRESS SWITCHES

DOWN

ENT

Current loop or RS485 module

Sensor connections

Ch1

GND

Figure 3.3 Location of press switches and 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)

Ch2

24V

3.4 Using display/keypad commands

3.4.1 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

HMP228

M210282en-A Operating Manual

with button s and the second line with button t; all selections are stored with ENTER. The selected quantities appear on the display also after power failure. After reset the transmitters are always in the display mode.

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

3.4.2 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; the desired 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.

3.4.3 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 on 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 programme returns to the previous display.

With some commands (e.g. calibration) 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.

The display commands are described in Appendix 2.

HMP228 Operating Manual M210282en-A

4. MAINTENANCE

4.1 Self-diagnostics

The HMP228 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 moisture and temperature sensors are damaged. If they are intact, send the transmitter to Vaisala for repairs. The error messages are listed in Appendix 3.

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:

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 3 for all error messages):

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

4.2 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.

Whatever the technique used, make sure that the reference instrument is at the same temperature as the checked instrument in order to avoid errors caused by temperature differences. 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.

ERRS <cr>

HMP228

M210282en-A Operating Manual

4.3 Moisture calibration

The HMP228 transmitter has been fully calibrated at the factory so there should be no immediate need for recalibration. The transmitter should be calibrated only if there is reason to believe that the adjustments have changed. The optimal interval for moisture calibrations depends on the process and the recommended interval varies from 3 months to 2 years.

NOTE

The HMP228 transmitter measures water activity in liquid/oil and the calibration is performed as for relative humidity transmitters. In calibration mode the transmitter automatically outputs relative humidity as the calibration parameter. It is essential to clean the sensor surface of oil before calibration; use e.g. instrument air or nitrogen to blow off the oil. Even the smallest amount of oil may destroy the salt solution.

NOTE

As oil performs a membrane over the sensor surface, the sensor's capability of absorbing moisture is slowed down. The stabilization time is thus at least double the time of a clean sensor; pay special attention to controlling the stabilization time.

A two-point calibration can be performed with Vaisala’s HMK15 or HMK13B Calibrator or the instrument can be sent to Vaisala. The instrument has to be recalibrated each time the moisture sensor is changed.

A Ø 13.5 adapter must be used when calibrating with the HMK13B Calibrator. The adapters (part no. 16611) can be ordered from Vaisala or Vaisala representatives.

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

When LED commands are used, relative humidity is output instead of water activity. When the transmitter is calibrated at two points, the points must be either 50 %RH or 50 °C apart from each other.

NOTE

If the sensor has been changed, perform a calibration according to Chapter

4.4.1.

HMP228 Operating Manual M210282en-A

4.3.1 Two point calibration procedure

A two point calibration should be performed in stable conditions using saturated salt solutions as references.

Disconnect the security lock jumper!

4.3.1.1 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.

• Insert the sensor head into the calibration hole of the LiCl chamber of

the humidity calibrator.

• Wait at least 30 minutes.

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

>CRH <cr> RH : 11.9 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> RH : 11.5 Ref1 ? 11.3 <cr> Press any key when ready...

• Insert the sensor head into the calibration hole of the NaCl chamber of

the humidity calibrator.

• Wait at least 30 minutes.

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

RH : 75.5 Ref2 ? yy.y <cr>

• The stabilization of the sensor can be monitored by entering c <cr>

instead of the reference value.

4.3.1.2 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.

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

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

0.05 %RH.

HMP228

M210282en-A Operating Manual

4.3.1.3 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.

• 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 (Chapter 4.4.5) and press ENT switch.

• Insert the sensor head into the calibration hole of the NaCl chamber in

the humidity calibrator.

• Wait at least 30 minutes.

• Check that the reading corresponds within the desired accuracy to the

value given in the calibration table (Chapter 4.4.5). 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.

4.3.2 One point calibration procedure

A one-point correction can be done manually in the field against an accurate reference but it is always recommended to perform a two point calibration.

Disconnect the security lock jumper!

4.3.2.1 Using serial commands

• Make sure that the sensors of the transmitter and the reference

instrument are close to each other. Allow enough time for the sensors to stabilize to the measurement conditions.

• Give command CRH <cr>, enter the humidity value and press <cr>.

>CRH <cr> RH : 11.9 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> RH : 11.5 Ref1 ? 11.3 <cr> Press any key when ready...

HMP228 Operating Manual M210282en-A

• Press any key and press <cr> when the transmitter requests the second

point value.

RH : 75.5 Ref2 ? yy.y <cr>

4.3.2.2 Using display/keypad commands

• Make sure that the sensors of the transmitter and the reference

instrument are close to each other. Allow enough time for the sensors to stabilize to the measurement conditions.

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

and then one point offset calibration RH 1 point cal. Change the humidity reading with the arrow keys to correspond the reference humidity and press ENT; pressing an arrow once changes the reading by 0.05 %RH.

4.3.2.3 Using LED commands

• Make sure that the sensors of the transmitter and the reference

instrument are close to each other. Allow enough time for the sensors to stabilize to the measurement conditions.

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

X2). If the outputs are already connected to e.g. a process computer and you do not want to disconnect them, the current output can be measured at separate test points located next to connector X15 (see the mother board).Give command ¡¡¡l. At the first calibration point the LED on the left flashes; adjust the humidity point (offset) with the arrow switches to the reference value. One push of a switch changes the output by 0.05 %RH; the change of the output voltage or current depends on the output scaling. Press ENT switch. The second LED from the left starts flashing; press ENT again.

4.4 Changing the moisture sensor

Remove the damaged sensor and insert a new one. Handle the sensor by the plastic socket. DO NOT TOUCH THE SENSOR PLATE. After sensor change, the moisture calibration must be performed according to the instructions in section 4.4.1.

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