Dew Point Mirror 973 Operation and Maintenance Manual MBW Calibration Ltd. Seminarstrasse 57 CH-5430 Wettingen / Switzerland +41 56 426 21 33 phone +41 56 427 14 00 fax 0Hwww.mbw.ch info@mbw.
Warranty MBW Calibration Ltd. (MBW) warrants the products it manufactures or distributes to be free of defects in material and workmanship under normal use and service when operated within the specified design limitations for a period of 12 months from date of initial shipment.
Table of Contents Table of Contents ..................................................................................................................... i Welcome ................................................................................................................................... 1 How to Use This Manual ......................................................................................................... 1 For More Information ..............................................................
REMOTE COMMUNICATION ............................................................................29 Introduction............................................................................................................................ 29 Hardware Connection & Cabling.......................................................................................... 29 Communications Settings .................................................................................................... 30 Command Syntax ......
Welcome Congratulations! With the 973 Dew Point Mirror you will be able to perform precision dew point and frost point measurements as well as measurements of other parameters such as relative humidity. The 973 utilizes a full color active matrix liquid crystal display with an integral touch panel. It has a high contrast ratio and a wide viewing angle for easy readability. Data is displayed in large easy to read fonts.
Operation Getting Started This section allows you to set up and start using the 973 right away. You’ll turn the system on and quickly familiarize yourself with the layout and features of the display and touch screen. Next, you’ll learn about the optical mirror assembly for later care and cleaning that may be required. Finally, you’ll use the 973 to measure the dew point temperature. Set your 973 on the bench and let’s get started! Turning the 973 On and Off The 973 needs a source of normal AC power.
Data Lines The first four lines of the display are for numeric or graphic representation of the measured data. We refer to those first four lines as data lines. 10.00 Relative Humidity % -9.8 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 the data over time. -10.2 -9.65 Time Span 00:30:00 20.16.
The Touch Screen The 973 utilizes a touch screen for user interaction. To activate a menu option or toggle a function on or off, simply touch the screen directly over the key or object desired. Calibrate the Touch Screen Before using the 973 for the first time, you may need to calibrate the touch screen to your finger positioning preference. Here’s how – 1. Press and hold the enter key on the numeric keypad for 3 or 4 seconds. If you’ve done it correctly, you’ll hear two loud short beeps.
Navigating the Menus The various menus of the right column of keys are navigated by using the key in the lower right corner of the touch screen. Each time you press the lower right key, a new menu appears on the keys directly above it. The menu is circular, meaning that once you go past the last menu, the first one 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 clear the menu.
Selecting Graph vs. Numeric Data Any data line may be viewed either as numeric or as a graph. The Numeric/Graphic menu is used to toggle any data line between numeric and graph mode. 1. Use the lower right menu key to select the Numeric/Graphic menu. ‘Numeric/Graphic’ appears on the key, and the keys above contain left pointing arrows. Notice that each key corresponds to the data line it points toward. 2. Press the arrow key corresponding to the data line you wish to change.
Selecting Units The data may be viewed in any of the many available units. There are two Units menus used to change the units of displayed data. 1. Use the lower right menu key to select the Units menu. ‘Units’ appears on the key, and the keys above contain current units indications such as ‘Temp °C’. Notice that each of the keys contain different types of units. In this case, the keys do not correspond to the adjacent data lines, but rather to different units types. 2.
The Measuring Head Assembly The heart of the 973 Dew Point Mirror instrument is the measuring head assembly. It is designed to be highly sensitive and accurate, yet rugged and easily accessible for periodic mirror cleaning. Although not required prior to initial operation, you may wish to familiarize yourself with the location and accessibility of the mirror and the other optical components within this assembly.
The Balance Indicator Balance Indicator + STABLE - Although it is directly obtained from the intensity of the mirror’s reflected light signal, the Balance Indicator is effectively the first derivative of the dew thickness. In other words, it indicates the rate of growth or decay of the condensed layer on the mirror. While the dew or frost layer is growing in thickness due to an increase in condensation on the mirror surface, the indicator is above center.
The input and output connectors are clearly labeled on the Sample Gas section of the back panel. Depending on the specific model and ordered options, the stainless steel gas input and output connections may be 6 mm Swagelok, ¼ inch Swagelok, or ¼ inch Cajon VCR. Note that you should never attempt to measure any gas with a dew point temperature that is at or above the temperature of the room. If you do, condensation will form inside the tubing.
System Configuration You may configure many aspects of the 973 based on your preferences at the time. For instance, you may easily select which humidity, temperature, and pressure values to indicate on the screen, the order in which they should appear, their units, and whether each will be shown as a number or as a graph. In addition to display configuration, you can also change how the 973 performs its control functions such as Dew/Frost determination, ORIS control, tube heating, mirror pre-cooling, etc.
Display Parameters Use the Parameters menu to select which parameters to display 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 if you turn the 973 off. See Selecting Parameters to Display on page 6 to select which values to display. A list of the available parameters follows. Note that not all parameters are available on all systems since some systems may not contain the associated hardware components.
Scaling Each graph can have its own scaling (or y-axis) values. There are three distinctly different scaling modes to choose from: Autoscale Fixed Range Maximum / Minimum You may also change the Time Span of the graph from this dialog. • Autoscale Autoscale mode determines 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 does the range of the graph.
5. Once the value is shown is what you want press the Ok button (or the enter key) to accept the new value, or press the Cancel button to abort all changes made to the mode and to any values. The only values that get accepted by the system are those that correspond with the selected mode. In other words, if you change the value of the Autoscale Minimum, but Fixed Range is the selected mode, the Autoscale Minimum value remains unchanged.
However, for mirror temperatures between 0 and approximately –30°C, the state of the condensed layer is generally indeterminate since dew can, and does, exist on the mirror in a meta-stable state at temperatures well below 0°C. In reality, the condensed layer on the mirror could be dew, frost, or some combination of the two. Significant errors can result if wrongful assumptions are made and can be in excess of 2°C.
Mirror Check Control Mirror Check is the process of warming the mirror to evaporate all condensation, look for the presence of contamination and account for it if necessary, then re-initiating a new dew or frost point measurement. Mirror Check may be initiated manually with the fixed Mirror Check key, or if enabled to do so, it may trigger automatically at pre-specified time intervals.
Changing Units You can display system data in any of a wide variety of units. When you make a new units selection, that selection remains until you change it again. To change units, follow the instructions given in the Selecting Units section on page 8. Units selections are global across the system, meaning that all values of that parameter type change to reflect the chosen units. For instance, changing the temperature units to °C forces all temperature data to appear in °C.
Specific Humidity Units Specific humidity may be displayed in units of g/g, g/kg, and lb/lb. When changing these units, specific humidity will change to reflect the new units selection, whether displayed numerically or as a graph. Notice that the chosen units will appear on the screen both on the units selection key and next to specific humidity when displayed.
Analog Outputs If this option is installed, the 973 is equipped with at least two analog outputs that are independently configurable. For each of the analog outputs, you may easily 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 discussed in the Menu Keys section on page 4. 2.
Scaling the Output to the Data With the appropriate configuration window displayed, you may change the data scaling of the analog output vs. the parameter. Continuing with the example in the previous paragraph, assume that you wish to have 0 to +1 VDC on the analog output represent 0 to +100 %RH.
Back Panel Connections Power Plug The power requirements are identified on the serial number label on the back of the instrument. Depending on the model, fuse access may also be available on or near the power plug. Power Switch The main power switch is mounted on the back panel near the power plug. Use the power switch to turn the system ON and OFF. RS-232 The RS-232 connector is used when connecting the 973 to an external computer.
Analog Outputs Analog outputs, if this option is installed, are used for connection of external voltmeters or chart recorders. The analog outputs are independently configurable. If you wish to make your own cables, the 973 requires a 2 pin connector, LEMO (www.lemo.ch) part number FGG 1B 302 CLAD 42. Red Dot aligns with Pin 1 When viewing the solder tubs of a disassembled 2-pin LEMO connector, pin 1 is usually identified with a full or partial circle drawn around it. Pin 2 should have no identifier.
Measurement Tips Since each particular 973 model is best suited for a specific dew/frost point range, it is important to have some minimal knowledge of the expected value of the measurement in order to ensure that the proper system is being used. In addition to proper system selection, your success will depend on other factors as well, such as selection and connection of hoses, cooling and/or heating requirements, flow rate, mirror cleanliness, and dew vs. frost determination.
Hose Input and Output Preferred Connections When comparing two or more instruments, make the connections in parallel. Pr Flow Pump Pr Flow Pump Troublesome Connections Never connect instruments in series, because of the interference between the two instruments.
Cooling Requirements Air Cooling All 973 systems are equipped with air cooling. When air cooled, the fan speed is controlled automatically by the computer. Air cooling is generally sufficient for measurements of frost/dew points from approximately –50 to +20°C. Air cooling operates automatically and requires no user input. Water Cooling The 973 is not equipped with any provisions for water cooling.
Installation Facility Requirements Environmental Your 973 is a precise laboratory quality instrument. While it does not require any special environmental control, it works best when the temperature is stable and free of rapid transitions. For operation, it is best when used under the following conditions: Operating Temperature 15 to 35°C Operating Humidity 5 to 95%RH non-condensing Power The 973 is equipped with a universal power supply capable of operation from 100 to 250 VAC at 50 to 60 Hz.
Remote Communication Introduction The 973 is equipped with a bidirectional RS-232 communications interface that allows it to be connected to a remote computer. This section is intended to provide necessary information for programming personnel regarding the use of the interface, including the hardware connections, communications settings, and the command syntax. Hardware Connection & Cabling Connect a computer to the 973 using a standard RS-232 9-pin extender cable.
Communications Settings To communicate with the 973, set your computer to the following settings. Baud Rate: Data Bits: Stop Bits: Handshaking: 9600 8 1 None 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 973 will be shown in this font.
Even if the command is not a request for data, but rather is a command to change a setpoint or parameter, the 973 still responds with a carriage return line feed combination. The following turns on the pump (if your unit is so equipped). Notice that no data is returned, but the 973 sends a CRLF acknowledgement that the command was valid. Pump.on = 1CR (sent by the computer to the 973) (the acknowledgement from the 973) C L R F However, if the command is unrecognized, the 973 does not respond.
Parameter Temperature Pressure Flow RH Absolute Humidity Specific Humidity Volume Ratio Weight Ratio PRT Resistance Units via RS-232 °C Pa l/m % g/m3 g/kg PPMv PPMw Ohms Some values simply require integer numbers such as 1 and 0 for On and Off, while others might need real numbers with a decimal point. The 973 recognizes both types of numbers and will attempt to convert the values you send to the correct format. For example, the number 0 means Off, while 1 or any other real or integer value means On.
Commands Listed By Functional Group Measurement Data Syntax DP? FP? RH? RHw? PPMv? PPMw? AH? SH? VP? P? Pa? Flow? Tx? Tp? Tm? Th? Om? Ox? Function Dew Point, °C Frost Point, °C Relative Humidity, % Relative Humidity (WMO), % Volume Ratio, PPMv Weight Ratio, PPMw Absolute Humidity, g/m3 Specific Humidity, g/kg Vapor Pressure, Pa Head Pressure, Pa Atmospheric Pressure, Pa Flow Rate, l/m External Temperature, °C Precooler Temperature, °C Mirror Temperature, °C Head Temperature, °C Mirror PRT Resistance, Ohms
ORIS Settings Syntax UseOris.on[=i][?] UseOris.below[=n][?] SaveCfg=973 Function 1 enables ORIS, 0 disables ORIS Temperature below which ORIS activates, °C Save these and other configuration parameters Mirror Cleaning Preparation Syntax MinHeadRemovalTemp[=n][?] SaveCfg=973 Function Head and inner cooler are warmed above this temp when Mirror Cleaning button has been pressed prior to head removal, °C Save these and other configuration parameters Automatic Mirror Check Syntax AMC.on[=i][?] AMC.
Analog Outputs (continued) Syntax Ana2.param[=i][?] Ana2.paramMin[=n][?] Ana2.paramMax[=n][?] Ana2.OutMin[=n][?] Ana2.OutMax[=n][?] Ana2.calGain[=n][?] Ana2.calZero[=n][?] Ana2.output=n Ana2.hold[=i][?] SaveCfg=973 Function Parameter to track with analog output #2 Min Value Max Value Min Voltage Max Voltage Gain calibration factor for D/A converter Zero calibration factor for D/A converter Use to set analog output when calibrating D/A converter. Automatically sets Ana2.hold=1. You must send Ana2.
Head Temperature Calibration Coefficients Syntax HeadTempCal.a0[=n][?] HeadTempCal.a1[=n][?] HeadTempCal.a2[=n][?] HeadTempCal.a3[=n][?] HeadTempCal.avg[=n][?] HeadTempCal.avgBand[=i][?] HeadTempCal.sensCode[=i][?] HeadTempCal.coefType[=i][?] SaveCal=973 Function Polynomial 0th order (Zero) coefficient, ~ 0 Polynomial 1st order (Span) coefficient, ~ 0.
Maintenance Mirror Cleaning The heart of the 973 dew point measuring instrument is the measuring head assembly. It is designed to be highly sensitive and accurate, yet rugged and easily accessible for periodic mirror cleaning. Removing the Head Cover Screw or Retaining Bar The measuring head is located on the right side of the 973 front panel. To gain access to the mirror and optoelectronic components, you must first remove the cover screw by twisting it counterclockwise.
Although a clean mirror is important to accurate measurements and sound measurement practices, please take the following comments into consideration. • • Never attempt to polish the mirror. It is slightly roughened at the factory to allow for better nucleation sites and thus better dew formation. If needed, the mirror may also be cleaned with methanol or alcohol. Always follow the use of these cleaning chemicals with water to ensure they are completely rinsed from the mirror surface.
