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MBW 473
User Manual
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ROTRONIC MBW 473 User Manual

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Operation and
Maintenance Manual
V2.0
Dew Point Mirror 473
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Warranty
MBW Calibration Ltd. (MBW) guarantees that its products are manufactured to the highest quality of material and workmanship specifications. MBW guarantees the reliability of its products for a period of 24 months from the date of initial shipment when operated in normal use and within the specified de­sign limitations. Under this Warranty, MBW will, at its discretion, repair or replace any component that upon examination by MBW or its duly authorized representatives proves to be defective during the warranty period provided the system is returned to the factory for inspection and repair shipping pre­paid. Improper or unauthorized maintenance, storage, repair, or alteration of any kind by personnel other than MBW or its duly authorized representatives may void all warranties. Warranty may also be voided for misuse, neglect, accident, corrosion, and improper installation. This Warranty is exclusive and in lieu of any and all other warranties of merchantability, fitness for a particular purpose, or any other warranty, expressed or implied, and all other liabilities and obligations on the part of MBW. MBW will not be liable for any other claims or damages, either direct, indirect, or consequential arising out of the use of its products.
MBW Calibration Ltd
Seminarstrasse 57 CH-5430 Wettingen / Switzerland +41 56 437 28 30 phone +41 56 437 28 40 fax sales@mbw.ch
www.mbw.ch
Subject to change without notice. For the latest version of this manual please visit our website. Copyright © 2012
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Table of Contents
WARRANTY ..................................................................................................... I
TABLE OF CONTENTS .................................................................................... II
1 INTRODUCTION ......................................................................................... 1
2 QUICK START ............................................................................................ 3
2.1 Unpacking ...................................................................................................................................... 3
2.2 Starting your 473 ........................................................................................................................... 4
2.3 Installing the Measuring Heads ..................................................................................................... 4
2.4 Dew Point Measurement ............................................................................................................... 5
3 GET TO KNOW YOUR 473 .......................................................................... 7
3.1 Front Panel .................................................................................................................................... 7
3.2 Back Panel ................................................................................................................................... 10
3.3 Measuring Heads ......................................................................................................................... 12
3.4 Carrying Handle ........................................................................................................................... 13
4 SYSTEM CONFIGURATION ...................................................................... 15
4.1 The Menu ..................................................................................................................................... 15
4.2 Selection of indicated Parameters ............................................................................................... 16
4.3 Selection of Numeric or Graphic Data Display ............................................................................ 17
4.4 Graph Scaling .............................................................................................................................. 18
4.5 Control Setup ............................................................................................................................... 20
4.6 Selection of Units ......................................................................................................................... 24
4.7 Analog Output Connections ......................................................................................................... 25
4.8 Selection of Color ........................................................................................................................ 28
5 SET UP AND OPERATION ........................................................................ 29
5.1 Measurement Set Up ................................................................................................................... 29
5.2 External Temperature .................................................................................................................. 30
5.3 Application Integration ................................................................................................................. 32
MBW473_MANUAL_E_V2.0 ii
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6 REMOTE COMMUNICATION .................................................................... 35
6.1 Hardware Connection and Cabling ............................................................................................. 35
6.2 Communication Settings ............................................................................................................. 36
6.3 Command Syntax ........................................................................................................................ 36
6.4 Command Reference .................................................................................................................. 38
7 MAINTENANCE ........................................................................................ 39
7.1 Calibrate the Touch Screen ......................................................................................................... 39
7.2 Ice Test ........................................................................................................................................ 40
7.3 Mirror Cleaning ............................................................................................................................ 42
7.4 Exterior Cleaning ......................................................................................................................... 43
7.5 System Information...................................................................................................................... 44
8 SPECIFICATIONS .................................................................................... 45
9 DRAWINGS .............................................................................................. 46
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1 Introduction
Precise and Stable Humidity Measurement
With the 473 Dew Point Mirror you are able to perform precise dew point measurements as well as measurements of other parameters such as relative humidity. The humidity measurement of the 473 is based on the chilled mirror condensation technology which provides highly precise, stable and repeat­able results.
Remote Measuring Heads with Temperature Probe
The 473 features two remote cable mounted measuring head options, the RP2 and the SH2. They are designed for direct insertion into applications with moving air. Both measuring heads are supplied with a PRT for precise temperature measurement and for the calculation of relative humidity.
Optional Pressure Measurement
Optionally, the 473 can be ordered with internal pressure measurement capability. This enables the instrument to compensate for pressure variations at the point of measurement.
LCD Display with Touch Panel
The 473 has a full color LCD touch panel with a high contrast ratio and a wide viewing angle for easy readability. Data is displayed in large, easy-to-read fonts. Using the on-screen buttons and menus, you can easily configure each line of the display for a variety of humidity, temperature, and pressure parameters that may be viewed in either SI or non-SI units.
Calibration
Users can check the 473 calibration at any time using the built-in Ice Test function, which provides instant verification of system accuracy and integrity.
Connect and Go
The system is ready for immediate use.
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2 Quick Start
This section guides you through the set-up and the first steps using your 473. It is a summary and should be used as a general overview and reference only. Do not use it as a substitute for the remain­der of the manual. To understand your instrument thoroughly, please read the other sections carefully.
2.1 Unpacking
The 473 is delivered in a custom-fit foam-lined Peli 1550 transport case. The following items are included in the case:
473 Dew Point Mirror SH2 or RP2 measuring head (as ordered) Temperature probe PT(100)
o The RP2 is supplied with a Ø3 x 30 mm PRT and a 0.5 m cable for extended connection
between the probe and the measuring head.
o The SH2 is supplied with a Ø2.1 x 100 mm PRT and a 0.5 m cable to connect the probe
to the measuring head and a 3 m cable to connect the probe directly to the back panel of the instrument.
2.5 m power cable 2 m measuring head cable Gas connections 6mm or ¼” Swagelok (SH2 only) Operation manual Calibration certificate
Before starting, carefully remove these items from the case and visually check for any signs of dam­age. If you are missing any item or find them damaged, please call the manufacturer or your local supplier. Make sure that the power rating on the back label corresponds to your power supply specifi­cation.
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2.2 Starting your 473
SH2
RP2
The 473 needs a source of AC power. It will work over a wide power range and will most likely operate at your local voltage and frequency. Look at the back panel label for the power requirements of your specific system.
1. Plug the supplied AC power cord into the back of the instrument, then into an AC outlet.
2. Turn the power switch to ON.
The display should become visible within a few seconds. If nothing happens, check the power source.
2.3 Installing the Measuring Heads
Depending on your order, the 473 is supplied with either of the following measuring heads:
The heart of the 473 Dew Point Mirror Instrument is a highly sensitive and accurate measuring head. Use the 19-pin measuring head cable (2 m) to connect the measuring head to the back panel of the 473. For further information on the measuring heads, please refer to sections 3.3 ‘Measuring Heads’ and
7.3 ‘Mirror Cleaning’.
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You can test the 473 dew point measurement by measuring the dew point tem­perature of the room.
First, make sure the measuring head is connected to the back panel of the 473. Next, start the measurement by pressing the Dew/Frost Control key. This button
enables the system to cool the mirror to the dew or frost point temperature, moni­tor the thickness of the condensation layer on the mirror, and precisely adjust the mirror temperature to maintain a stable condensation layer. When Dew/Frost Con­trol is enabled, the indicator on the key will turn green and the dew or frost point temperature display will begin to show the mirror temperature as it cools to the condensation point.
See section 4.2 ‘Selection of indicated Parameters’ for information on selecting the parameters you wish to have displayed.
The SH2 measuring head is equipped with a fan to pull a gas sample across the measuring head. If you are using the SH2 measuring head, press the Fan key on the touch screen to turn the fan on/off. For further information on the fan refer to section 3.3 ’Measuring Heads’.
Fan
2.4 Dew Point Measurement
When you switch on the 473, all readings on the display may initially be blank. If your instrument is equipped with a pressure sensor, the pressure reading will be displayed. After connecting the measur­ing head or temperature probe you will get an external temperature reading. To measure humidity (dew point, frost point, %RH, etc.), the Dew/Frost Control mode must be enabled and gas must be flowing across the mirror. If %RH readings are required, an external temperature probe must be con­nected. To connect the external temperature probe, see section ‘External Temperature Probe’ on page 11. Alternatively, a fixed external temperature may be entered via the touch screen. Please fol­low the instructions in section 5.2 ‘External Temperature’.
Fan
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Menu Keys
Status Line
Fixed
Function Keys
Data Lines
Keypad
3 Get to know your 473
3.1 Front Panel
The front panel of the 473 is equipped with a full color touch screen and a keypad for data entry. To activate a menu option or toggle a function on or off, simply touch the desired key or object directly on the screen.
When the 473 is turned on, the display will activate within a few seconds. A sample display configura­tion is shown below. The display configuration can be customized, so your display may look different. The use and the functions of the display are described in the next chapter.
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Data Lines
If numeric, a data line contains the value to the left, with the parameter description and units to the right.
If graphic, a data line shows a simple graph of data over time.
Near the bottom of the display is the Sta­tus Line. The Status Line displays Bal- ance, Density, Contamination, and, optionally, Battery Power.
The first three lines of the display show a numeric or graphic representation of the measured data. We will refer to these first three lines as Data Lines.
Data can be displayed in different parameters and units either numerically or graphically. Please refer to section 4, ‘System Configuration’ to learn how to configure your preferences.
Status Line
Balance
Although it is directly obtained from the intensity of the mirror’s reflected light signal, balance is effec­tively the first derivative of the dew thickness measurement. It indicates the rate of growth or reduction of the condensation layer on the mirror. While the dew or frost layer on the mirror surface is growing, the indicator will be above center. The faster the layer is growing, the higher the indication. Converse­ly, when the layer on the mirror surface is evaporating, the indicator will be below center. The faster it disappears, the lower the indication. When the indicator is in the center, the thickness of the dew or frost layer is neither growing nor evaporating, and the layer on the mirror surface is in equilibrium with the gas. In this center position of the indicator, there is no net exchange of water vapor between the gas and the mirror surface. If the humidity of the gas sample is homogeneous and of low enough vari­ability for the control system to sense a steady value, the Balance indicator will show a green Stable message, accompanied by a few short beeps.
Density
The Density Indicator graphically depicts the approximate thickness of the dew or frost layer on the mirror surface. The 473 can automatically differentiate between dew and frost layers and the indicator will display the current condensation state. The label in the density indicator will change from Layer Density (when the state of the layer is uncertain) to either Dew Density or Frost Density (when ei­ther dew or frost is being measured). For more information regarding Dew/Frost point determination see section ‘Dew / Frost Control’ on page 20.
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The bottom line of the display contains a row of fixed function keys. These keys are used to start and stop the fan (only for SH2), initiate a mirror check, initiate mirror cleaning, and switch dew/frost control on or off. For further infromation on the fan see section 3.3, for the other funcitons see section 4.5.
On the right hand side of the display there is a column of menu keys. The bottom, dark gray key changes the cur­rent menu by cycling to the next menu. Each of the light gray keys change their label and function based on the menu that is currently selected.
Use the dark grey
Mirror Residue
The Mirror Residue Indicator graphically shows the amount of mirror contamination that was detected during the last mirror check. If the bar covers more than a quarter of the space, we recommend that you clean the mirror.
Fixed Function Keys
Menu Keys and Navigation
key on the bottom (menu selection key) to move between menus.
The menu selection is circular. Once you go past the last menu, the first one will appears again and the process starts over. You can use the ± key on the keypad to move backward through the menus. Use the Enter key to exit the menu.
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3.2 Back Panel
Power Switch
The main power switch is on the back panel above the power plug. The power supply has a built-in fuse and will automatically switch off in case of overload. To restart power, the main power switch must be switched off and on again.
Power Plug
The supplied power cord is connected to the power socket on the instrument back panel. The sup­ported power supply voltage is 100-120 VAC / 200-240 VAC at 50 to 60Hz. The power requirements are specified on the serial number label on the back of the instrument.
RS-232
The RS-232 port can be used to connect the 473 to a desktop or laptop computer. The necessary 9­pin RS-232 (serial) extender cable is a common accessory and can easily be obtained at any comput­er store.
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Optional Analog Outputs
The 473 can be ordered with two optional analog outputs which are independently configurable. For each of the analog outputs, you can choose which parameter to track and how to scale the selected parameter to the analog output range. Please refer to section 4.7 ‘Analog Output Connections’ to learn how to configure the analog outputs.
Internal Barometric Pressure Sensor
As an option you can order an internal barometric pressure sensor to measure ambient pressure. To measure chamber pressure or to calibrate the sensor, connect a 3 mm Swagelok tube to the pressure sensor port on the back panel.
Measuring Head Connection
The 473 can be ordered with two different types of measuring heads; the RP2 and the SH2. Both measuring heads are connected to the back panel of the 473 with the supplied 19-pin measuring head cable.
External Temperature Probe
The external temperature probe is used to measure the temperature of the environment that is being tested. To obtain certain humidity parameters, such as %RH, an external temperature measurement is necessary. External temperature measurements are not required for dew or frost point measurements.
The SH2 is supplied with a Ø2.1 x 100 mm PRT temperature probe. The probe can be con-
nected to the 473 in the following ways:
1. Use the supplied 4-pin 0.5 m cable to connect the probe to the measuring head.
2. Use the supplied 5-pin 3 m cable to connect the probe directly to the back panel of the instrument.
The RP2 is supplied with a Ø3 x 30 mm PRT temperature probe. The probe can be connected
to the 473 in the following ways:
1. Plug the temperature probe directly into the connector on the top of the RP2 measuring head.
2. Use the supplied 4-pin 0.5 m cable to connect the probe to the measuring head.
3. Use the optional 5-pin 3 m cable (available from the manufacturer) to connect the probe directly to the back panel of the instrument.
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3.3 Measuring Heads
1. Gas Inlet
2. External Temperature Connection
3. 19-pin Measuring Head Cable Connection
4. Flow Fan
5. External Temperature Probe (Ø2.1 x 100 mm) with 0.5 m Cable (4-pin)
6. 19-pin Measuring Head Cable (2 m)
7. Screw Cover
8. Measuring Head Front Part
9. Guide Pin
10. Polished mirror
1
2
3
4
5
6
7
8
9
10
The SH2 Measuring Head
Fan
The fan of the SH2 measuring head is used to generate the necessary gas flow to the measuring head, when no other gas flow is available. The fan can be removed and replaced with an output con­nector (Swagelok SS-6M0-1-2RS) for direct connection of gas tubing to other instruments.
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1. Temperature Probe Ø3 x 30 mm
2. Measuring Head Assembly
3. 19-pin Measuring Head Cable (2 m)
4. When reassembling the measuring head take care to align the red marks.
5. External Temperature Connection
6. Polished Mirror
To adjust the position of the carrying han­dle, press the buttons on both sides. Re­lease the buttons when the handle is in the desired position. Ensure that the handle has locked into place before lifting the instru­ment.
1 2 3
4
5
6
The RP2 Measuring Head
3.4 Carrying Handle
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Parameter
This menu is used to select the parameters displayed on the data lines.
Numeric/Graphic
This menu is used to toggle a data line between numerical and graphic display.
Control Setup
This menu is used to configure the control functions like Dew/Frost Control or the Mirror Check.
Units
This menu is used to select the units in which you would like the data to be displayed. Unit changes will be applied to all values displayed on the screen, such as temperatures, pressures and concentrations.
Foreground Color
The menu Fore Color is used to temporarily change the color of the lines drawn on graphs and the color of text (numbers and letters). The foreground color of each data line can be changed individually. Unlike other settings, the color settings will be restored to the standard color settings when the 473 is restarted.
Background Color
The menu Back Color is used to temporarily change the color of the background of the numeric or graphic data lines. The background color of each data line can be changed indi­vidually. Unlike the other settings, the color settings will be restored to the standard color set­tings when the 473 is restarted.
4 System Configuration
Many aspects of the 473 can be configured depending on your measuring needs and preferences. You can choose which humidity, temperature, and pressure values will be indicated on the screen, their order and units, and whether each will be shown as a number or as a graph. In addition to the display options, you can define how the 473 performs its control functions, such as Dew/Frost deter­mination. Any changes in the configuration settings will remain active until the next time they are changed. Color settings will be restored to the standard settings after restarting the instrument.
4.1 The Menu
The 473 has several menus to configure the system to meet your requirements. Use the dark gray menu selection key to cycle through each of the menus. Each time you press the menu selection key, the respective label will indicate which menu is currently active. Use the ± key on the keypad to move backward through the menus.
Use the Enter key on the numerical keypad to exit the menus. This is not necessary, however, as staying in a specific menu will not affect the measurement.
List of available menus:
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4.2 Selection of indicated Parameters
Parameter
Explanation
Dew Point
The temperature to which a gas must be cooled to start condensing water vapor to liquid water. Dew point is pressure dependent and must be stated together with its associated pressure.
Frost Point
The temperature to which a gas must be cooled to start deposition of water vapor in the form of ice. Frost point is pressure dependent and must be stated together with its associ­ated pressure. Frost point exists only below 0 °C. While not technically correct, it has been common industry practice to report values below 0 °C as dew point, although frost point is the correct term. For further explanation on dew or frost point refer to ‘Dew / Frost Control’ in section 4.5.
%RH
The ratio between the amount of water vapor in a sample and the maximum amount possi­ble at that same temperature and pressure.
%RH WMO
The ratio between the amount of water vapor in a sample and the maximum amount possi­ble at that same temperature and pressure calculated using the World Meteorological Or­ganization (WMO) formula.
Volume Ratio
The ratio between the water vapor volume and the total volume of the sample gas, general­ly expressed in parts per million by volume, ppmv or its numerical equivalent μl/l. Once determined, ppmv has no further pressure dependence. It is also independent of the gas type or mixture.
Weight Ratio
Weight ratio is the ratio between the mass of water vapor and the total mass of the sample gas, generally expressed in parts per million by weight, ppmw or its numerical equivalent mg/kg. Once determined, ppmw has no further pressure dependence, but depends on the gas type and mixture through the molecular weight of the constituents.
Absolute Humidity
The weight of water vapor per unit volume of humidified gas.
Specific Humidity
A ratio of the water vapor to the total weight of the humidified gas.
Vapor Pressure
The partial pressure exerted by vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature. It is usually expressed in kPa.
Head Pressure
The pressure of the gas sample in the measuring head.
External Temp
The temperature measured by the external temperature probe.
Head Temp
The temperature measured by the PRT in the measuring head.
In the Parameter menu you can choose which parameters you would like to have displayed on the data lines. When you select parameters for display on any of the four data lines, those selections re­main valid until you change them again, even after you turn the 473 off. Below you will find the list of the available parameters.
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Follow the steps below to choose the parameters you wish to have displayed on the four data lines:
1. Select the Parameter menu by pressing the dark gray menu selec­tion key until Parameter appears. Small left pointing arrows will appear on the four upper menu keys.
2. Press the arrow key next to the data line you wish to change. Each time you press the arrow key, the parame­ter of the respective line will change. Continue pressing the arrow key until the parameter you wish to view is displayed.
3. Change the parameters on any of the other data lines the same way.
4. If you choose the parameter External Temp, but have not connected the external temperature sensor, no reading will be displayed. If you choose parameters that require the measuring head to be connected, such as Frost Point, Dew Point, Head Temp, % RH, Humidity, Volume Ratio, Weight Ratio, Vapor Pressure, or Head Pressure please make sure all the relevant equipment is connected for the instrument to be able to display the chosen parameters.
4.3 Selection of Numeric or Graphic Data Display
Any data line may be viewed either in a numeric or a graphic format. The 473 automatically keeps a short data history of every selectable parameter so that a graph appears instantly whenever a data line is switched from numerical to a graphic mode. Use the Numeric/Graphic key to toggle any data line between numerical or graphic mode.
1. Use the dark gray menu selection key to select the Parameter menu. Small left-pointing arrows will appear on the four upper menu keys.
2. Press the arrow key next to the data line that you wish to change. The data line will toggle be­tween numerical and graphic mode each time you press the key.
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4.4 Graph Scaling
Each graph can have its own x and y-axis scaling and range settings. There are three different scaling modes to choose from; Autoscale Minimum (which is the default setting), Fixed Range or Mini- mum/Maximum. Each of these is explained in more detail below. You can change the graph scaling and switch between the three scaling modes at any time.
1. On the screen, touch the graph you wish to change. A graph scaling dia­log box will appear. One of the but­tons in the Description column will have a green indicator. This shows you the currently selected mode.
2. If you would like to change the scal­ing mode, touch the button of the mode you would like to select. Note that for the Minimum/Maximum op­tion, only the Maximum button needs to be selected (the Minimum is then automatically selected by the sys­tem).
3. Touch the corresponding field in the Change To column, next to the range that you have selected.
4. Using the numerical keypad, enter the value needed. If you make a mistake while entering the value, touch the field you are editing on the screen. With each touch, the last digit in the field will be erased.
5. Once you have entered the correct value, press the Ok button (or the enter key on the numeric key­pad) to confirm. Press the Cancel button if you wish to abort all changes made in the dialog box.
Any values you enter will only be accepted by the system if they correspond with the selected mode. If, for example, you enter a value into the bracket next to the Autoscale Minimum, but Fixed Range is the selected mode, the Autoscale Minimum value will remain unchanged.
Autoscale Minimum
The Autoscale Minimum mode is the default setting for this instrument. This mode sets the scaling automatically so that all of the stored data will be visible on the graph at the best possible resolution. As the range of the data changes, so will the range of the graph. In Autoscale Minimum mode, you can select the minimum range that you want the graph to scale to. For viewing temperature and dew or frost point graphs, setting the Autoscale Minimum to a value of 0.1 or greater is generally a good choice. It allows the graph range to close in on the data as it stabilizes at a single value without the range of the y-axis becoming too narrow.
For example, setting an Autoscale Minimum of 0.1 while the 473 is displaying a graph of a steady dew point measurement of 20.0 °C will set the minimum and maximum value limits of the graph to 19.95 °C and 20.05 °C, respectively. The graph will also zoom out as needed if a reading goes outside that range. You can experiment with this value to determine your personal preference.
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Fixed Range
The Fixed Range mode allows you to select a fixed range for the graph’s y-axis. It automatically cen­ters on the most recent data point. As the most recent data varies, so will the center point of the graph, leaving the overall range fixed. The Fixed Range mode is mostly used to monitor data for stability. For example, if you set the fixed range for the external temperature graph to 0.2 and the current data is
23.00 °C all data between 22.80 °C and 23.20 °C is visible on the graph.
Minimum/Maximum
In the Minimum/Maximum mode you can specify the minimum and maximum values used for the graph’s y-axis. Unlike the other modes, the visible range of the graph’s y-axis will not automatically change if a data point is outside the set minimum/maximum range. If the data points are outside the specified range, you will not see them on the graph.
Time Span
Time Span determines the number of minutes of the data history that is visible on the graph. The 473 stores a fixed number of data points independent of the selected time span. Thus, changing the time span will change the time interval at which the data points are stored. The total number of stored data points will not change. With a time span of 15 (15 minutes), the graph data is sampled and stored every few seconds. With a time span of 120 (2 hours), the graph data is only sampled, stored, and updated about once a minute.
When you change the time span, the data that was sampled and stored at the old interval will be in­crementally replaced by new data sampled at the new interval. The time span indicated on the graph will always reflect the actual time span of the data that is displayed on the graph, and will agree with the time span you selected once enough data points have been sampled. The selected time span is common to all graphs, so they will always have the same time relationship to one another.
The time span can be changed in the Numeric/Graphic menu:
1. Touch the graph you wish to change on the screen. The Graph Scaling dialog box will appear.
2. Touch the Change To: field next to Time Span. The field will turn white.
3. Use the numerical keypad to enter an even value between 2 and 1440. As you enter the value it will appear in the white Change To: field of the dialog box.
4. If you make an entry error, touch the field that holds the number you wish to change. Each time you touch the field, the last digit entered will be deleted.
5. Press the OK button in the dialog box or press Enter on the key board to confirm the new value. Press Cancel to leave it unchanged.
6. The result will take some time to show as the old data at the old time interval will be replaced by data at the new time interval gradually as determined by your selected time span.
If you prefer to see the same measurement as both numerical value and graph, you may select the same parameter on two data lines, and set one line to graph mode and the other to numeric mode. See sections 4.2 and 4.3 for instructions on selecting displayed parameters and changing their display modes.
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4.5 Control Setup
Using the Control Setup menu enables you to control the manner in which the 473 operates.
Dew / Frost Control
When measuring dew/frost points between 0 °C and -20 °C, condensation on the instrument’s chilled mirror may be in the form of dew, frost, or a combination of both. If the state of the condensation is not known, it will introduce errors into all the humidity measurements reported by the instrument.
To eliminate this potential source of error, the Force Frost function is used to rapidly cool the mirror to below -20 °C, forcing all dew on the mirror into frost. The mirror will then re-stabilize at the frost point temperature. Once the condensate layer is in a state of frost, it will remain frost for all sub-zero mirror temperatures, allowing the instrument to measure the frost point accurately. The dew point and all other humidity measurements are then mathematically calculated from the frost point.
To change the Force Frost settings:
1. Select the Control Setup menu by press­ing the dark gray menu selection key un­til Control Setup appears.
2. Touch the Dew/Frost Control button. The Mirror Dew/Frost Control window will open.
3. The Force Frost function can be enabled or disabled by clicking on the Force Frost Below button. If the indicator on the left side of the button is green, Force Frost is enabled. If the indicator is grey, Force Frost is disabled.
4. To adjust the temperature below which Force Frost activates, click on the Change To: field to the right of the Force Frost Below button. The field will turn white.
5. Enter the temperature in degrees C below which Force Frost should activate.
6. If you make an entry error, touch the field that holds the number you wish to change. Each time you touch the field, the last digit entered will be deleted.
Press the OK button in the dialog box or press Enter on the keyboard to confirm the new value. Press Cancel to leave it unchanged.
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Why it is Important to Distinguish Between Dew and Frost
For mirror temperatures above 0 °C, water vapor always condenses on the mirror in its liquid phase (dew). A condensation layer on a mirror above 0°C is therefore al­ways considered a dew point.
Although ice always starts melting at exactly 0 °C, water will not necessarily freeze at 0 °C. Water may
stay in its liquid phase at temperatures far below 0 °C. This phenomenon is referred to as ‘Super-
Cooled Water’.
The fact that water at subzero temperatures can condense either as dew or as frost makes it some­what difficult to determine whether the condensate layer on the mirror at temperatures below 0 °C is liquid or solid. Various factors such as contaminants, time, pressure etc. may cause the condensate layer to remain liquid at mirror temperatures of –20 °C and below.
It is furthermore important to understand that the difference in the temperature at which the liquid or the solid condensate layer stabi­lizes can be up to 3 ˚C. As shown on the picture to the right, it is also possible that dew and frost exist concurrently on the mirror which results in a non-stable value reading somewhere between the dew and frost point.
Therefore the phase of the condensate must be known in order to avoid significant errors and to correctly calculate all humidity val­ues, including vapor pressure, dew point, %RH, volume ratio, weight ratio, absolute humidity and specific humidity.
It would be desirable for manufacturers and users of humidity instruments to use the term frost point for temperatures below zero and dew point for temperatures above zero. While not technically correct, it has been common practice to use dew point for temperatures below 0 °C, although frost point would be the correct term. As discussed above, dew point can exist below 0 °C in the form of super-cooled water and is different in value from the equivalent frost point temperature. For the same vapor pres­sure, the frost point is approximately 10% of reading above the corresponding dew point value (when expressed in °C). For example, a vapor pressure of 38 Pa corresponds to a frost point of −30 °C and a dew point of −33 °C. From a measuring perspective it seems obvious that a clear and consistent dis- tinction between dew and frost point is important.
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Mirror Cleaning
Activating the Mirror Cleaning function with the respective key at the bottom of the screen will heat the mirror to a pre-specified temperature, getting the measuring head ready for the removal of the cover and the optical assembly. If the mirror and other internal measuring head components are disassem­bled while they are cold and become exposed to normal atmospheric air, the possibility of undesired condensation exists. Warming the mirror and other internal components to a safe head removal tem­perature, greater than or equal to the current ambient temperature, will prevent the formation of dew on the mirror assembly during servicing.
To set the Minimum Mirror Temperature when activating the Mirror Cleaning mode:
1. Select the Control Setup menu by pressing the dark gray menu selection key until Control Setup appears.
2. Touch the Mirror Cleaning menu button.
3. Touch the Change To: field to the right of the Minimum Mirror Temp label.
4. Enter the temperature in degrees C which the mirror must warm to during the Mirror Cleaning mode,. It is recommended that you enter your current ambient temperature or higher.
5. If you make an entry error, touch the field that holds the number you wish to change. Each time you touch the field, the last digit entered will be deleted.
6. Press the OK button in the dialog box or press Enter on the keyboard to confirm the new value. Press Cancel to leave it unchanged.
Mirror Check
Mirror Check is the process of warming the mirror to evaporate all condensation, looking for the pres­ence of contamination and accounting for it if necessary, then initiating a new dew or frost point meas­urement. Mirror Check may be started manually with the fixed Mirror Check key, or if enabled, it will start automatically at pre-specified time intervals.
During a mirror check, whether triggered automatically or manually, the indicator on the fixed Mirror Check key has the following meanings:
Red: The mirror is heating.
Brown: The mirror is holding at the programmed Mirror Check Temperature.
Yellow: The mirror is cooling to re-form the dew or frost layer.
Gray: The mirror check function is not currently active.
Once the system has re-established a dew or frost layer and become stable, the mirror check function is completed and the color indicator turns gray.
After the Mirror Check is completed the bar of the Mirror Residue Indicator shows the amount of con­tamination on the mirror. If the bar covers more than a quarter of the space, we recommend that you clean the mirror. For instructions on mirror cleaning, please refer to section 7.3 ’Mirror Cleaning’.
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Automatic Mirror Check
To view or edit the Mirror Check parameters, press the Mirror Check key of the Control Setup menu.
If automatic mirror checks are desired, se­lect it by pressing the Cycle Time button. A green light on the button indicates that au­tomatic mirror check is enabled.
When the automatic mirror check is enabled, the Mirror Check key at the bottom of the screen shows a countdown timer indicating the time before the next auto­matic mirror check is performed. In the automatic mode, the mirror check may still be initiated manually by pressing the Mirror Check button.
Cycle Time
The Cycle Time is the number of minutes between automatic mirror check operations. Use the numer­ical keypad to enter the desired cycle time in minutes.
Heating Time
The Heating Time determines how long the mirror check temperature will be held before allowing the next dew or frost point measurement. A heating time of 0 means that the instrument will resume dew or frost point measurement immediately upon reaching the mirror check temperature. If a heating time greater than 0 is entered, the mirror will heat and remain at that temperature for the chosen duration. Heating time is effective regardless of whether mirror check is triggered automatically or manually.
Temperature
Edit the Temperature field to change the temperature, in degrees C, that the mirror will be heated to, and optionally held at during Mirror Check.
If you have entered a wrong value into a field and want to erase it, press the entry field to backspace.
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4.6 Selection of Units
Temperature Units
°C, °F or K
Pressure Units
Pa, hPa, MPa, atm, bar, mb, inHg, mmHg, cmHg, inH2O, mmH2O, cmH2O, Torr or psia
Flow Rate Units
l/min, ml/min, l/h, cfm, or cfh
Weight Ratio Units
PPMW (Parts Per Million by Weight) or PPBW (Parts Per Billion by Weight)
Absolute Humidity Units
g/l, g/m3, or lb/ft3
Specific Humidity Units
g/g, g/kg, or lb/lb
Vapor Pressure Units
Pa, hPa, kPa, MPa, atm, bar, mb, inHg, mmHg, cmHg, inH2O, mmH2O, cmH2O, Torr, or psia
You can display system data in any of a wide variety of units. When you change units, your selection will remain until you change it again. Unit selections are global, which means that all values of that parameter type across the whole system will change to the chosen units. For example, changing the temperature units to °C will display all temperature data in °C.
Data retrieved via RS-232 will always be in SI units regardless of the units chosen for display. Also note that settings within dialog boxes used for changing system parameters are entered and displayed in SI units. Units only affect the four data lines.
Available units are:
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The 473 requires a 4-pin LEMO connector (www.lemo.ch). Part Number: FGG 1B 304 CLAD 42.
Voltage
[V]
Current
[mA]
+10
20 2 4 0 0
-10
N/A
Pin
Signal
Position
Description
1
+V
When viewing the solder tubs of a disassembled 4-pin LEMO connector, pin 1 is usually identified with a full or partial circle drawn around it. Pin 4 should have no identifier. When wiring the cable, note that the pin numbering of the socket in the back panel of the instrument starts at the top left (pin 1) and goes counter-clockwise (as viewed from the rear of the unit).
2
-V
3
+I
4
-I
The red dot is between pin 1 and 4.
4.7 Analog Output Connections
The 473 can be ordered with two optional analog outputs which are independently configurable. If the instrument is ordered with the optional analog outputs, a 4-pin LEMO connector will be supplied
with the instrument, which can be used to fabricate a custom cable for your application.
When the 4-pin LEMO connector is properly assembled, the red dot of the connector housing should be between pin 1 and 4.
The 473 allows both a voltage and a current output signal. As shown in the illustration above, pins 1 and 2 supply the voltage signal (V), and pins 3 and 4 supply the current signal (I). Inside the instrument, the output signal is connected to a D/A converter and then split into a voltage and a current signal. Therefore you may use either a volt or current meter to receive the analog signal. The maximum voltage output range is -10…+10 V. See the following table to identify the corresponding current signal.
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Configuration of Optional Analog Outputs
Parameter
Units
Enter this #
Dew Point
[°C]
0
Frost Point
[°C]
1
RH
[%]
2
RH WMO
[%]
3
Volume Ratio
[PPMv]
4
Weight Ratio
[PPMw]
5
Absolute Humidity
[g/m3]
6
Specific Humidity
[g/kg]
7
Vapor Pressure
[Pa]
8
Head Pressure
[Pa abs]
9
Flow Rate
[l/min]
10
External Temperature
[°C]
11
Head Temperature
[°C]
12
For each of the analog outputs, you may select which parameter to track and how to scale the select­ed parameter to the analog output range. These selections are made for each of the analog outputs via the Analog Outputs menu.
1. Access the Analog Outputs menu with the menu selection key.
2. To make the selections for the first analog output, press the Analog Output 1 key.
3. Use the numerical keypad to enter the desired values. For details on each op­tion, read the three following subsections.
4. Follow the same procedure for the se­cond or any subsequent analog outputs as needed.
Selection of Parameter to Track
In the analog configuration window, enter the number which corresponds to the parameter you wish to track. Use the following table to identify which number to enter into the Parameter field. For example if you wish to track the external temperature, enter number 11 into the entry field next to Parameter.
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Scaling the Output Signal
Use Min Value and Max Value to set the range of the Parameter, and use Min Voltage and Max Voltage to set the range of the analog output signal.
Example 1
1. You want to track the parameter %RH as an analog voltage output. The previ­ous table shows that the parameter %RH has been allocated number 2. En­ter number 2 into the field next to Pa- rameter.
2. The next step is to define the range of %RH which will be covered with the ana­log output signal. You want to have the whole range of 0…100%. Enter 0 into the field next to Min Value and 100 into the field next to Max Value.
3. Then, set the scaling of the analog output signal. You want to have 0…1 VDC on the analog out­put to represent the 0…100 %RH. Enter 0 into the field next to the Min Voltage and 1 into the field next to Max Voltage.
Example 2
To keep things simple, we will take the same Parameter, Min Value and Max Value settings as in the first example. However, this time you want the analog output range to be scaled to mA instead of volts. Your selected range is 4…20 mA for the parameter range of 0…100 %RH. In order to enter this into the system, please refer to the table on page 26 to find the voltage which corresponds to your desired
mA output range. You will find that 2…10 V
corresponds to 4…20 mA. Thus, enter 2 into the field next to Min Voltage and 10 into the field next to Max Voltage.
Calibration Adjustment
D/A Cal Gain and D/A Cal Zero are used to adjust the analog output signal accuracy. This adjustment is made at the factory and will rarely need to be changed by the user.
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4.8 Selection of Color
1. Access the Fore Color menu. Fore Color will appear on the dark gray
menu key, and the keys above will show left-pointing arrows. Note that each of the upper keys correspond to the data lines they point to.
2. Press the arrow key of the data line you wish to change. Note that the foreground color of the data line will change with each touch of the key.
3. Change the foreground color on any of the other data lines the same way.
1. Access the Back Color menu. Back Color will appear on the dark gray menu key, and the keys above will show left-pointing arrows. Note that each of the upper keys correspond to the data lines they point to.
2. Press the arrow key of the data line you wish to change. Note that the background color of the data line will change with each touch of the key.
3. Change the background color on any of the other data lines in the same way.
The foreground and/or background color of any data line can be changed in the Fore Color and Back Color menus. Access the Fore Color and Back Color menus with the menu selection key. To revert to the default color scheme, press and hold key number 9 on the keypad for a few seconds until the instrument beeps.
Foreground Color
The foreground color is the color of the numbers and letters. To change a data line’s foreground color:
Background Color
To change a data line’s back color:
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5 Set Up and Operation
5.1 Measurement Set Up
Back Panel Connections
The following picture shows the back panel of a fully connected 473 with RS-232 cable, 19-pin meas­uring head cable, power cable and the Ø2.1 x 100 mm PRT on the 3 m cable.
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5.2 External Temperature
Set Fixed External Temperature
If you do not use an external temperature sen­sor, you have the possibility to enter a fixed external temperature. Set the parameter so that External Temp shows on one data line (see section 4.2). If no temperature sensor is in­stalled, the data line will not show any reading. Touch the External Temp data line on the screen. A window (see picture below) will ap­pear where you can enter the desired tempera­ture.
Enter the desired temperature in degrees C (21 °C in this example) and activate the Use Fixed Ext Temp option by touching the button. When the indicator square turns green, the fixed external temperature is active.
The External Temp data line (and the graph, if shown) will now say “(fixed)”. As shown in the image on the right, the external temperature will immediately change to the temperature that was entered, and will remain there until it is changed again.
If you want to start using an external tempera­ture probe, go to the Fixed External Tempera-
ture window and press the Use Fixed Ext Temp to disable the fixed external temperature
function. The green square will turn grey.
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If you wish to make your own thermometer cable, the 473 re­quires a 5 pin LEMO connector (www.lemo.ch), part number FGG 1B 305 CLAD 42.
Pin
Signal
Position
Description
1
Shield
When viewing the solder tubs of a disassembled 5-pin LEMO connector, pin 1 is usually identified with a full or partial circle drawn around it. Pin 5 should have no identifier. When wiring the cable, note that the pin numbering of the socket in the back panel of the instrument starts at the top left (pin 1) and goes counter-clockwise (as viewed from the rear of the unit).
2
+I
3
+V
4
-I
5
-V
Red Dot aligns with Pin 1
Use your own External Temperature Sensor
The External Temperature plug on the back panel is used for the connection of an external tempera­ture probe. External temperature measurements are required if certain humidity parameters, such as %RH, are to be computed. External temperature measurements are not required for dew or frost point measurements.
After identifying pin 1, follow the line counter-clockwise from pin 1 to all other pins in succession. Wire the cable according to the following scheme:
When the 5-pin LEMO connector is properly assembled, the red dot of the connector housing is located directly above pin 1.
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5.3 Application Integration
The 473 is suitable for many applications over the humidity and temperature ranges detailed in Sec­tion 8 ‘Specifications’. When installing the measuring head into a system, the operating temperature of the measuring head and the mirror cooling capacity must be carefully considered. A high measuring head temperature will limit the lowest frost/dew point that can be reached; from a head temperature of 20 °C, the mirror cooling capacity is approximately 50 °C. This means that the lowest frost point with a head temperature of 20 °C will be approximately -30 °C. If the mirror cooling is at its maximum capaci­ty but cannot cool the mirror to at least a few degrees below the dew/frost point, the dew point or head temperature will display a constant value above the actual dew/frost point and the Dew Density on the status line will remain at 0 (zero).
Since the principle of dew point measurement requires the mirror to be cooled to a temperature where condensation forms, the transfer of heat is important in order to attain the best measurement capabil­ity. If the body of the measuring head is in contact with other surfaces, these may cause additional heating or cooling which are either useful or detrimental to measurement performance, so always take time to consider the thermal properties of the measuring head and any items in its environment and their possible effects.
The following application examples are included to show some of the most common applications of the 473. In all cases, temperature effects are discussed and there may be similar implications in your system.
Climatic Chamber Validation
A widely used method for validating or calibrating the working volume of a climatic chamber is to use a chilled mirror to measure dew point temperature of the chamber environment. In combination with single or multiple point temperature measurement, %RH values can be derived. Multiple temperature measurement in a chamber is often referred to as ‘mapping’, and this method is described in IEC 60068.
The 473-SH2 is well suited for this application. The SH2 measuring head can be positioned anywhere within the chamber’s working volume, either on a chamber shelf or directly attached to the chamber surface. Direct surface contact be­tween the base of the measuring head and the chamber surface can be beneficial for improv­ing heat transfer from the measuring head. Heat transfer tape or paste can be used to further improve thermal contact.
Adequate airflow through the SH2 measuring head is important in order to provide stable and repeatable measurements. The integrated fan in the SH2 measuring head can be used to provide the needed airflow through the meas­uring head. If necessary for your application, an extension sample tube can be added using 6mm or ¼” Swagelok fittings as shown.
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At equilibrium, the water vapor pressure is assumed to be ho­mogenous, but the user should determine this by experimenta­tion according to the type of chamber being tested.Temperature probes should be positoned according to the need for validation. The most common arrangement is four probes in the top corners, four in the bottom corners and a single probe in the center. For larger chambers, more probes can be added so that the entire working volume is measured. This allows for the full spatial volume to be temperature mapped. By combining this temperature data with the measured dew point, %RH can also be mapped. Software such as that supplied with the MBW T12 temperature system can be used to display and record the dew point, temperature and calculated %RH values. Please contact MBW or your local supplier for more information.
RH Generator Validation
Transportable RH Generators provide a convenient and fast way of calibrating RH instruments. Most use RH sensor con­trol probes to measure and control the conditions in the gen­erator’s test chamber. The standard calibration uncertainty of the RH generator is limited by calibration drift, linearity and temperature coefficients of the control probe. With the use of a dew point mirror, with its inherent stability and precision, the uncertainty can be significantly improved.
The 473-RP2 is ideal for this application. As shown, the RP2 measuring head is introduced into the generator chamber through a front access port. The measuring cell of the mirror is exposed to the moving air within the chamber and measures the temperature and humidity of the air as it passes over the measuring head. As with climatic chambers, it is assumed that, at equilibrium, water vapour pressure is homogenous throughout the chamber volume. Provided that the temperature is stable and uniform, the %RH derived from the dew point and temperature measurement is suitable for use as a transfer standard for calibration of the generator’s control probe or as a reference against which units under test can be compared.
Temperature Effects
Most RH generators are also able to control temperature. This means that RH probes can be calibrated for temperature at the same time as %RH. The RH calibration can be performed at working temperature. As RH is highly temperature dependent, temperature effects and gradients, in particular, must be considered. With the RP2 probe installed into the RH generator chamber, the Peltier element that is used to cool the mirror causes heat to be dissipated from the body of the measuring head. This can cause temperature gradients within the generator chamber.
Page 38
The user must therefore determine this effect experimentally for the conditions used. In the example installation shown above, the RP2 measuring head and the chamber door are thermally coupled to allow for optimum dissipation of heat generated by the measuring head. At equlibrium, the generator will establish a thermal equilibrium within the complete system so that temperature stability is optimized and gradients are minimized.
Whereas the RP2 head-mounted temperature probe (PRT) can be used for the measurement of temperature in most measurement situations, in some chamber conditions a short extension cable may be advisable to thermally ‘decouple’ the PRT from the measuring head. . Especially at low RH conditions, where the mirror temperature can be much lower than the chamber temperature, the heating of the measuring head can cause appreciable temperature errors . Therefore, consideration of this possible effect must be included within uncertainty budgets. In calibration laboratories where the lowest possible uncertainties are required, the implementation of continuous multi-point temperature measurement allows the user to determine gradients dynamically. In such small chambers, four or six PRTs arranged around the working volume is sufficient according to IEC 60068.
Condensation
If the RP2 probe is installed through the chamber ports of an RH generator working at high tempera­ture, a thermal gradient through the RP2 may result and the probe may be at a slightly lower tempera­ture than the chamber. This may cause condensation to form on the outer body of the RP2 probe. As a result, the measured dew point values will be incorrect. It is even possible that condensation on the head will cause a short circuit. To avoid such problems, make sure that the RP2 probe is inserted as far as possible into the chamber volume. More advanced RH generators feature heated doors which prevent condensation.
Working or Transfer Standard
In the calibration laboratory or workshop, the 473 provides the best possible measurement capability for a working standard in RH generators. By using the 473 for continuous dew point and temperature reference measurement, users can achieve small uncertainties and calibrate multiple probes in short time periods.
When an RH generator is used for on-site calibration, the combination of the RH generator, dew point mirror and temperature measurement system may not be practical for site engineers as they need to run calibrations quickly to minimize down-time. Examples of this situation include calibration of instru­ments used in pharmaceutical production rooms, laboratories, and critical industrial processes. In this case, the RH generator can be periodically validated using the 473 as a reference standard.
The user should define a working procedure to manage calibration traceability. Maintaining careful calibration records and history for both the transfer standard and the generator is essential to properly determine the calibration stability and drift components of uncertainty budgets. For further support, please contact MBW or your local distributor.
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Signal
473
(9 pin)
Direction
Computer
(9 pin)
Computer
(25 pin)
1 1 8
*TxD
2  2
3
*RxD
3  3
2
DSR
4  4
20
*GND
5
5
7
DTR
6  6
6
CTS
7  7
4
RTS
8  8 5 9 9 22
6 Remote Communication
The 473 is equipped with a bidirectional RS-232 communications interface which allows connection to a computer. This section provides the necessary information for the use of the interface, including the hardware connections, communications settings, and the command syntax.
6.1 Hardware Connection and Cabling
Connect a computer to the 473 using a standard RS-232 9-pin extender cable. The extender cable has a male connector on one end and a female connector on the other. If your computer has a 25-pin serial port connector rather than a 9-pin connector, you will also need a 25-pin to 9-pin port adapter. Both the 9-pin RS-232 extender cable and the 25-pin to 9-pin port adapter are commonly available at most computer hardware dealers.
The 473 ignores the DSR and CTS handshaking signals. While there is no harm in connecting all 9 pins, the 473 only requires connection of three of the pins (pins 2=TxD, 3=RxD and 5=GND). For your reference, the complete connector pin-out is listed in the following table. Note that the signals identi­fied by * are required, while the others are optional.
* Denotes a required connection. All others are optional.
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6.2 Communication Settings
Baud Rate:
9600
Data Bits:
8
Stop Bits:
1
Handshaking:
None
To communicate with the 473, set your computer to the following configuration:
6.3 Command Syntax
This section details the general syntax guidelines regarding termination, leading and trailing spaces, case sensitivity, and numeric values. Throughout this section, characters originating from the comput­er will be shown for illustrative purposes in this font. Characters originating from the 473 will be
shown in this font.
General Use
All commands require a question mark to indicate you are requesting data. When requesting data from the 473, follow the command with ?, the question mark character. For example, the following requests the current pump status.
Pump.on?
The 473 will reply with the current pump status (1 = on, 0 = off).
Termination Characters
All commands must be terminated with either a carriage return nation
CRL
.
F
Regardless of the command sent, the 473 will reply with a carriage return linefeed the response, provided the command is recognized as valid. Here is an example:
C
DP?
(sent by the computer to the 473)
R
-10.015
CRL
(sent by the 473 back to the computer)
F
If the command is unrecognized, the 473 does not respond. See example below.
Abcdef?
C
(invalid command sent from the computer)
R
C
or a carriage return linefeed combi-
R
CRL
at the end of
F
(no response from the 473)
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Parameter
Units via RS-232
Temperature
°C
Pressure
Pa
Flow
l/m
Volume Ratio
PPMv
Weight Ratio
PPMw
Leading and Trailing Spaces
The 473 ignores leading and trailing spaces. It also ignores spaces before and after equal signs and question marks. For example, both the following commands are perfectly valid.
Dp?
Dp ?
C
R
C
R
However, the following command is invalid since spaces are embedded within the keywords.
D p?
C
R
Case Sensitivity
All commands are insensitive to case. For example, the commands DP?, Dp?, dP?, and dp? will trig­ger identical responses from the 473. They will return the measured dew point value.
Numerical Values
All numerical data received from the 473 is either in standard or in scientific notation. Receiving a number as 12.34 is the same as receiving it as 1234e-2 or as 1.234e1. Depending on the value of numerical responses the 473 sends out, it may send the numbers in either standard or scientific nota­tion.
Numeric data is never appended with text of any kind. When requesting a temperature related value, only the numeric portion of the value is sent. The units are assumed.
The following table lists the units of the numerical data that the 473 returns, regardless of the units selected on the touch screen display or set via the RS-232. When you change units (even if you change them via RS-232), you affect only what is seen on the display. All numerical values retrieved from the RS-232 will always be in the following units.
Page 42
6.4 Command Reference
Syntax
Function
DP?
Dew Point, °C
FP?
Frost Point, °C
RH?
Relative Humidity, %
RHw?
Relative Humidity (WMO), %
PPMv?
Volume Ratio, PPMv
PPMw?
Weight Ratio, PPMw
AH?
Absolute Humidity, g/m3
SH?
Specific Humidity, g/kg
VP?
Vapor Pressure, Pa
P?
Head Pressure, Pa
Tx?
External Temperature, °C
Tm?
Mirror Temperature, °C
Th?
Head Temperature, °C
Om?
Mirror PRT Resistance, Ohms
Ox?
External PRT Resistance, Ohms
Syntax
Function
ID?
Returns a string containing instrument identifica­tion, i.e. DPM 473
IDN?
Returns only numeric portion of identifier, i.e. 473
Below you will find a list with all available commands grouped by function. All commands are consid­ered read-only values.
Measurement Data
System Identification
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With the tip of your finger, press the center of the yellow key in the upper right-hand corner of the touch screen. The key will turn grey and another key will turn yellow.
Now touch the yellow key in the lower left-hand corner of the touch screen. The key will turn grey and you have successfully calibrated the touch screen.
Test your new touch screen calibration by pressing the bottom right menu selection key several times. If it does not work to your satisfaction, repeat the calibration.
7 Maintenance
7.1 Calibrate the Touch Screen
Before using the instrument for the first time, or when the instrument is used by different operators, you may need to calibrate the touch screen to your finger positioning preference. Left and right hand­ed people, for example, may have different points of pressure when using the touch screen.
To calibrate the touch screen: Press and hold the Enter key on the numerical keypad for 3 to 4 seconds. You will hear two short
beeps and the key in the upper right corner will turn yellow.
Page 44
7.2 Ice Test
Press the menu selection key on the lower right to select the Units menu. Then press the Ice Test button.
Please note that the Ice Test will start immediately after the Ice Test button has been pressed.
During the Ice Test, the mirror rapidly cools to approximately
-30 °C. Because the measuring head is open, humidity from
the ambient air starts to condense on the mirror. This forms a frost layer on the mirror which can be facilitated if neces­sary by blowing on it. After reaching the low temperature and forming ice on its surface, the mirror begins to heat. As the temperature approaches 0 °C, the instrument will beep in­creasingly rapidly as the mirror gets closer to the ice-melting temperature.
Watch the mirror closely. As soon as the mirror temperature reaches 0 °C, the ice will melt into liquid water drops (phase transition).
The measuring accuracy can be checked with a simple, built-in test. The test may be performed at any time, and is recommended whenever the results of your normal measurements do not correspond to expectations, and you suspect that there may be an error with the instrument.
The mirror must be visible to perform the Ice Test. If you have an SH2 measuring head, remove the measuring head cover prior to the Ice Test as described in section 7.3 ’Mirror Cleaning’. If you have an RP2 measuring head, disassembly is not necessary as the mir­ror is visible from the outside.
The Ice Test cannot be started as long as a dew/frost point measurement is in progress. Make sure that the bar on the Dew/Frost Control key is grey.
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When you observe the phase transition on the mirror, press the Ok button. The mirror temperature is measured at that moment and a dialog box appears with the test results.
If the measured ice-melt temperature was in the range of ±
0.2 °C, the check is successful and will be indicated with the
calibration status PASS.
If the measured ice-melt temperature was outside the range of ± 0.2 °C, the check was not successful and will be indicat­ed with the calibration status FAIL. In this case the ice test should be repeated. If it continues to fail, the instrument should be sent to the manufacturer or an authorized agent for evaluation and/or repair.
Press the Ok button on the PASS/FAIL status window.
The next window requests that you clean the mirror. Clean and reassemble the measuring head as described in
section 7.3 ’ Mirror Cleaning’.
Page 46
7.3 Mirror Cleaning
To access the mirror and the opto-electronic compo­nents, remove the measuring head cover.
The cover looks like a large, tan-colored knurled knob. To remove it, simply turn it counterclockwise. It re­quires approximately three full turns to completely unscrew it.
Once the screw cover has been removed, remove the black optical assembly (optical head) by pulling it straight towards you. The loose half is the optical as­sembly containing the light emitting and light sensing opto-electronic elements and the gold contacts. The other half contains the mirror, temperature sensor, and some mating gold contacts. Avoid touching the mirror and gold contacts with your fingers to prevent contam­ination.
Clean the mirror with a clean cotton swab or a lint free tissue.
Never attempt to polish the mirror. If necessary clean the mirror with metha-
nol or alcohol. Then clean the mirror with distilled water to ensure the cleaning chemicals are completely removed from the mirror surface.
At the heart of the 473 is the measuring head assembly. It is highly sensitive and accurate, yet easily accessible for periodic mirror cleaning. To ensure high accuracy, the mirror should be cleaned before starting a measurement. Inspect the mirror carefully. Use a magnifying glass, if necessary. If there are signs of contamination or if you suspect that contamination is present, use the following procedure to clean the mirror.
SH2 Measuring Head
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Page 47
To access the mirror and the opto-electronic components, remove the optical assembly from the measuring head. The two red dots indicate where the measuring head and optical assem­bly will separate. When reassembling the measuring head after cleaning make sure the two red dots align as shown in the picture.
To remove the optical assembly, pull the two halves of the measuring head apart. The loose half is the optical assembly containing the light emitting and light sensing opto-electronic ele­ments and gold contacts. The other half con­tains the mirror, temperature sensor, and some mating gold contacts. Avoid touching the mirror and gold contacts with your fingers to prevent contamination.
Clean the mirror with a clean cotton swab or a lint free tissue.
Never attempt to polish the mirror. If necessary clean the mirror with
methanol or alcohol. Then clean
the mirror with distilled water to ensure the cleaning chemicals are completely removed from the mirror surface.
RP2 Measuring Head
7.4 Exterior Cleaning
Front Panel
The 473 front panel is completely sealed and can easily be cleaned with liquid glass cleaner or other mild cleaning chemicals applied to a cloth. Clean the front panel periodically as needed.
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7.5 System Information
When you press the System Info button in the Analog Outputs Menu a window appears which
gives you information about the model of the in­strument, the version of the software and the serial number of the instrument.
44 MBW473_MANUAL_E_V2.0
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Specifications
473-RP2
473-SH2
Measuring Ranges
Frost/Dew Point Relative humidity Temperature (head mount PRT) Temperature (cable mount PRT)
-20…70 °C 5…100 %RH
-20...80 °C
-50…100 °C
-30…70 °C 2…100 %RH
-20…80 °C
-50…100 °C
Accuracy
Frost/Dew point Temperature
≤ ± 0.1 °C (-20…70 °C), ± 0.2 °C ≤ ± 0.1 °C
Reproducibility
Frost/Dew point Temperature
≤ ± 0.05 °C ≤ ± 0.05 °C
Standard Features
Temperature probe
Digital I/O Display Thermoelectric mirror cooling Mirror temperature sensor Gas connections Transport case Power cable Operating instructions Calibration certificate
RP2: Ø3 x 30 mm PRT, 0.5 m cable SH2: Ø2.1 x 100 mm PRT, 0.5 and 3 m cables RS-232
5.7” LCD with color touch screen 2-stage with typically 50 °C depression at 20 °C ambient Platinum Resistance Thermometer (Pt100) 6 mm or ¼” Swagelok (SH2 only) Custom fit foam-lined Peli 1550
2.5 m English Factory calibration: 5 points FP/DP, 3 points temperature Upgrade to SCS accredited ISO17025 calibration available
Optional
Int. barometric pressure sensor Analog outputs
0.1% or 0.01% accuracy, 700…1200 mbar User programmable, 2x 4…20 mA or 0…10 V
Additional Information
Power supply Operating conditions:
Instrument Measuring heads
Storage conditions
100…120 VAC / 200…240 VAC, 50/60 Hz, 100 Watt (auto switching)
0…40 °C, 90 %RH non-condensing 20…80 °C, 99 %RH non-condensing
-20...50 °C
Weight & Dimensions
Dimensions Weight Protection
Instrument
W310 x H155 x D265 mm 5 kg IP54
In Transport Case
W510 x H220 x D450 mm 12 kg IP65
We reserve the right to change design or technical data without notice.
8 Specifications
Page 50
46 MBW473_MANUAL_E_V2.0
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Side View
9 Drawings
Page 52
Front View
48 MBW473_MANUAL_E_V2.0
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Top View
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