OPTI-CAL Integrated Humidity Calibrator · The Kahn OPTI-CAL Integrated Humidity Calibrator is a high precision, yet simple to operate, humidity calibration system designed for calibrating

Issue September 2004 KAHN INSTRUMENTS, INC. 885 Wells Road, Wethersfield, CT 06109

Tel: 860-529-8643; Fax: 860-529-1895 E-mail: [email protected] www.kahn.com

OPTI-CAL Integrated Humidity Calibrator

INSTALLATION, OPERATION AND

MAINTENANCE MANUAL

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KAHN INSTRUMENTS, INC. 885 Wells Road, Wethersfield, CT 06109Tel: 860-529-8643; Fax: 860-529-1895

E-mail: [email protected]

CONTENTS

1. INTRODUCTION ................................................................................................................... 3

1.1 General........................................................................................................................... 3 1.2 Calibration ..................................................................................................................... 3 1.3 Manufacturing Quality ................................................................................................... 4

2. INSTALLATION..................................................................................................................... 5

2.1 Initial Setup .................................................................................................................... 5 2.1.1 Filling the Water Reservoir................................................................................... 5 2.1.2 Emptying the Water Reservoir............................................................................. 5 2.1.3 Installing the Chamber RH Probe and Temperature Probe ............................. 5 2.1.4 Installing Test Probes for Calibration.................................................................. 7

2.2 Electrical Connections.................................................................................................. 7 2.2.1 Power Supply ........................................................................................................ 7 2.2.2 Digital Communications ....................................................................................... 8

3. OPERATING CONTROLS................................................................................................... 9

3.1 Operating Overview...................................................................................................... 9 3.1.1 Chamber Temperature and Humidity Settings.................................................. 9 3.1.2 L.E.D. Status Indication........................................................................................ 9 3.1.3 Display Controls ..................................................................................................10

3.2 Operating Procedure..................................................................................................11 3.3 Dynamic Contamination Correction (DCC).............................................................12 3.4 Data Hold Phase of the Chilled Mirror Sensor ........................................................13 3.5 Chilled Mirror Sensor Display Screens ....................................................................14

4. MAINTENANCE..................................................................................................................18

4.2 Desiccant Replacement.............................................................................................18 4.3 Cleaning the Chilled Mirror Sensor...........................................................................19

5 APPLICATION SOFTWARE .............................................................................................21

5.1 Virtual Hygrometer ......................................................................................................21 5.2 Parameter Setup.........................................................................................................22 5.3 Charting and Logging.................................................................................................24 5.4 Statistics ......................................................................................................................26 5.5 Control Parameters ....................................................................................................26 5.6 Calibration Correction................................................................................................27 5.7 Change of Password..................................................................................................29

6. TECHNICAL SPECIFICATION .........................................................................................30

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1. INTRODUCTION

1.1 General

The Kahn OPTI-CAL Integrated Humidity Calibrator is a high precision, yet simple to operate, humidity calibration system designed for calibrating relative humidity instruments. OPTI-CAL provides an atmospheric pressure calibration environment that has been carefully designed to give excellent stability and accuracy over the range 10 to 90 % relative humidity (RH) and for chamber temperatures between 10 to 50 ºC. The OPTI-CAL is designed as a bench top, self-contained instrument requiring only power and an occasional filling of the saturator with distilled water for normal operation. Within the climatic chamber, an accurate, stable and homogeneous environment is produced by a sophisticated control system, which varies a mix of circulated dry and saturated air and, uniformly controls the chamber temperature throughout its entire volume. An integral optical (chilled mirror) sensor provides continuous confirmation of the humidity within the chamber and provides a fundamental and traceable reference measurement for all key parameters of interest. The operation of OPTI-CAL is achieved by setting the set points for % RH and temperature by the front panel controls or by an external input while mounting the humidity probes requiring calibration through the chamber door via a series of mounting ports that have been designed to accommodate all common sizes of RH probes.

1.2 Calibration

Our Humidity Calibration Laboratory is accredited by UKAS for dew-point measurements in the range -90 °C to +82 °C dew point (calibration accreditation number 0179). It is also traceable directly to the National Institute of Standards & Technologies (NIST) USA over the range -75 °C to +20 °C dew point. Our full range calibration facility extends from -100 oC to +90 oC dew point. A Certificate of Dew-Point Calibration is provided with the instrument, which means that the instrument has been calibrated against Kahn Calibration Standards. It is also possible to provide a UKAS Calibration Certificate giving direct calibration traceability of the instrument to NPL Standards. Please contact the Kahn Technical Sales Department for further details.

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1.3 Manufacturing Quality

Your OPTI-CAL should reach you in perfect working condition. Rigorous procedures at every stage of production ensure that the materials of construction, manufacturing, calibration and final test procedures meet the requirements laid down by our Quality System.

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2. INSTALLATION

2.1 Initial Setup

Please check that you have received all items listed on the packing list. The enclosure is designed for bench top mounting in a laboratory type environment and on a level platform. It should be positioned in a clean and level location. Allow sufficient clearance at the rear of the enclosure for maintenance and ventilation. The instrument is not designed as a fully portable equipment set, but can be easily moved to any suitable location for use, while ensuring that any water in the instrument reservoir is drained (See 2.1.2 below.) with the chamber control RH probe removed. The instrument should NOT be moved while in operation.

2.1.1 Filling the Water Reservoir

Before operation the water reservoir located on the front panel requires filling with distilled water. Tap or demineralized water should NOT be used. To fill the water reservoir, remove the filling port blanking cap and by using the filler bottle supplied with the OPTI-CAL, carefully fill the reservoir with clean distilled water to a level between the two indicator lines. Do NOT fill beyond the “MAX” indicated line, as this may cause liquid water to enter the humidity chamber and adversely effecting the control process. Replace the cap after filling.

2.1.2 Emptying the Water Reservoir

Before transporting the OPTI-CAL, or when the system is not going to be used for a few weeks or more, it is essential to drain the water reservoir. To do this, first remove the blanking caps at the top and base of the water reservoir and then simply allow the water within the system to drain into a suitable container. Refit the blanking caps. Do not re-use any drained quantity of water within the system

2.1.3 Installing the Chamber RH Probe and Temperature Probe

For optimum response speed, an internal RH probe is used with an adaptive servo-loop to control the humidity within the chamber. A temperature probe for the reference Optidew is also used. To avoid damage to both probes while in transportation, they will need to be installed upon receipt of the instrument. However, installation is a simple procedure of locating the appropriate connectors within the chamber and connecting the probes in.

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PCB TOP VIEW

rh P

RO

BE

TE

MP

ER

AT

UR

E P

RO

BE

Probe connectors on the PCB inside the chamber.

CAUTION: If the unit is to be transported the probes should be removed to prevent damage.

Fig. 1 Probe Connectors

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2.1.4 Installing Test Probes for Calibration

RH probes requiring calibration can be fitted through the chamber door. Five probe mounting ports are available varying in sizes from 8, 12, 12.5, 18,5, & 24 mm in diameter. Also supplied is a kit of blanking plugs to allow any unused ports to be capped when not in use. Probes requiring calibration can also be placed totally within the chamber and signal connections made via the 25 way D type connector mounted at the rear of the chamber. For wiring details of this connector refer to Figure 2.

Blanking Ports Inserting RH probes for calibration.

2.2 Electrical Connections

2.2.1 Power Supply

A single phase power supply between 88-264 V is required to operate this unit. The power supply connection is a 3-pin IEC plug located on the rear panel of the instrument. The power ON/OFF switch is in the same location adjacent to the power socket as the power input fuse. A 3-conductor power cable is provided, the free end of which should be wired to a suitable ground plug. Power cable conductors are color coded according to the convention: Brown L (Live) Blue N (Neutral) Green/Yellow G (Ground)

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WARNING! This instrument must be connected to electrical ground for safety.

2.2.2 Digital Communications

Located on the front panel is a 9 way ‘D’ connector, which can be used to communicate with the OPTISOFT application software or by an ASCII terminal program. The communication interface is RS232 as standard or RS485 as a factory settable option.

Pin number RS232 RS485

2 Tx B

3 Rx A

5 GND GND

Test Probes A 25 way D type connector located on the front panel, can be used to directly connect to test probes, mounted inside the chamber. Also on this connector are analog input and output connections for control of the chamber. For further details see Figure 2.

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3. OPERATING CONTROLS Check all connections are in accordance with the installation instructions.

3.1 Operating Overview

All the instrument manual settings are achieved by use of the controls positioned at the top right of the instruments front panel. At the far right hand side are the setting switches for chamber temperature.

3.1.1 Chamber Temperature and Humidity Settings

These push switches are used to select the required chamber temperature setting in 0.1 ºC increments or chamber humidity setting in 0.1 % RH. The slider switches are used to select either “Auto” for external control or “Man” for front panel setting. The “On” and “Off” slider switch enables the temperature control system. The maximum setting limit of temperature is +50 ºC. If there is no external interface controlling the system and the slider switches are set to “Auto” the system will default to 50 % RH @ +20 ºC.

3.1.2 L.E.D. Status Indication

In the lower right hand side of the front panel, status LED’s are provided.

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Temperature: Directly below the temperature setting controls, four LEDs indicate that the chamber is being heated (yellow) or cooled (green). It is normal for these LEDs to continually flash as they control the chamber. Humidity: Directly below the humidity setting controls a single LED indicates the status of the humidity system. Yellow indicates humidifying is in progress: Green indicates de-humidifying is in progress.

3.1.3 Display Controls

To the right of the front panel display is a single multi-function button marked ‘DISPLAY CONTROL’, which enables the user to select between two operation modes of the reference optical sensor and to scroll through the measured and calculated parameters such as ambient temperature, or relative humidity and, indications of the system status. The mode can be either LOCAL or REMOTE. In LOCAL mode, the display is active and data such as dew point and temperature is displayed whereby RS232 output is not available. In REMOTE mode the display is inactive and the RS232 output is available. To change between the two modes simply hold down the display control button for approximately 5 seconds until the display changes mode. The mode can be changed at anytime except when display is showing the start-up banner. In remote mode the display will show *REMOTE MODE*.

HUMIDITY

TEMPERATURE

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3.2 Operating Procedure

The procedure is as follows:

• Load the relative humidity probes, which require calibration into the ports in the chamber door, and ensure that the chamber door is fully secured.

• Switch on the power. The chilled mirror sensor will enter the DCC mode.

• The display will initially show test characters for approximately 0.5 second, after

which the start-up banner will be displayed for approximately 7 seconds & in LOCAL mode.

• After the start up banner has expired, the display will show screen 1. This displays

the status of the optical mirror sensor. To scroll to screen 2, firmly but momentarily, press the display control button. It is not possible to view any other screens until the DATA HOLD period is complete. Note that there may be a small delay before the display changes to the next screen; this is normal. After the DATA HOLD period has finished screen 3 will appear. All eight screens can now be accessed by depressing the display control button.

• Using the humidity and temperature setting switches, set the % RH & temperature

required and allow sufficient time for the instrument to thermally stabilize before monitoring humidity/dew-point readings.

• Typical response times for various step changes are shown below. T100 represents

the total time taken to reach stability at the new set point. T63 and T95 values represent the times taken to reach 63% and 95% respectively of the step change in relative humidity and/or temperature. Times are in minutes.

Temp, °C RH % T63 T95 T100 Start 25 20 Step 1 15 20 =12 =23 =26 Step 2 15 50 = 2 = 3 = 5 Step 3 15 80 = 3 = 7 = 9 Step 4 25 20 = 3 = 5 =14 Step 5 25 80 = 3 = 8 =10

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3.3 Dynamic Contamination Correction (DCC)

To alleviate the problems of measurement accuracy due to contamination, a totally new contamination compensation system has been designed for the optical sensor. Dynamic Contamination Correction (DCC) automatically eliminates any error that may be caused by mirror particulate contamination. DCC is a self-learning system that adapts itself to operating conditions, predicts and reacts to the real requirements for contamination correction to achieve optimum transmitter performance at all times. Although the DCC system is fully automatic, it can be user configured to accommodate your own process conditions. As further protection in extreme conditions, sintered stainless steel or porous membrane guard options are available. Either guard can also be used as a flow limiter in high velocity direct insertion applications. At switch-on the optical sensor will enter DCC, energize the Status Relay and display the status. During this phase, the mirror surface is heated above the ambient dew point to measure mirror contamination, while Channel 1 mA output is held at 23 mA until the system has made a measurement. The next time the optical sensor enters DCC, this output will be held at a level equivalent to the measured value before DCC is started. As part of the DCC system, the optical sensor determines the change in contamination from the previous DCC and if above a predetermined level will initiate an enhanced boost of the heat-pump drive to ensure no residual condensation is present before determining a new contamination value.

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DCC Min Hold Time

Measurement Time

DCC

Time

Temp

Extended DCC

Mirror Contamination > 2% from last DCC

Mirror Temp Boosted

3.4 Data Hold Phase of the Optical Sensor

During Data Hold, the level of the Channel 1 mA output will be held, the Status Relay energized and Status displayed, until the system has stabilized onto the measured dew point. The Data Hold phase will finish when the following two conditions are met: i) the minimum hold time has expired ii) the system is stable to within a specified stability band. The minimum hold time is nominally set to 4 minutes, and generally under most conditions the system will be stable within this time period. However, there may be some conditions where the system may take longer to stabilize, so under these conditions an adaptive hold algorithm takes over to determine when stability is reached. If under extreme conditions the system fails to stabilize to within the set stability band, the Data Hold phase will terminate when the maximum hold time is reached.

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When the Data Hold finishes, the Status Relay will de-energize, and Channel 1 mA output will be set to a value, which represents the measured value of the selected measurement parameter. The system will now be in its continuous measurement phase, where it will remain until the measurement time has elapsed and the next DCC cycle initiates.

Temp

DCC Min Hold Time

Adaptive Hold

Time

Hold On Analog O/P Released

3.5 Optical Sensor Display Screens

Below is a description of the parameters and system status information shown on each screen. Screen 1: Status of the optical sensor. It will show DCC, DATA HOLD, OPTICS ALARM or MEASURE according to the current status of the chilled mirror sensor. Screen 2:

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Peltier power and the Mirror condition. The peltier power indicates how much the heat pump is depressing in order to measure the dew point. When the peltier power has a value of 100 % and does not reduce over an extended period of time, it means that the heat pump is at maximum depression. In normal operation this indicates that the dew point is lower than the present mirror temp and therefore cannot be measured. Reducing the sensor ambient temperature by use of additional cooling will increase the measurement range of the instrument in applications where the Peltier power > 95 %. Along side the Peltier power value is an indicator that shows the control stability. When this indicator shows CNTRL, it indicates the system is controlling the mirror temperature on the dew point. COOL indicates system is depressing the heat pump, in order to form dew on the mirror surface. HEAT indicates a rapid increase in dew-point level, whereby the system needs to increase the temperature of the mirror surface to read this new dew-point value. The Mirror Condition indicates the amount of signal received back from the mirror, which includes both the level of moisture and contamination on the mirror surface. In DCC mode, this display will only show the amount of mirror contamination and if greater than 80 % after a DCC, will initiate an optics alarm condition. Screen 3: Humidity in % RH and ambient temperature. Screen 4: Humidity in dew point and ambient temperature. Screen 5: Humidity in gkg-1 and ambient temperature. Screen 6: Humidity in gm-3 and ambient temperature. Screen 7: The first line in this screen displays ?(t – tdp) which is the difference between ambient temperature and dew point. Note that this parameter will be equal to 0 if the dew point is higher than the ambient temperature (e.g. during a DCC cycle). The second line displays the ambient temperature.

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Screen 8: The first line displays aw, which is equivalent to RH/100. The second line displays ambient temperature. See diagram on the following page for details.

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Apply Power

Initialising OPTI-CAL

Screen 1

Screen 2

Screen 3

Screen 4

Screen 5

Screen 6

Screen 7

Screen 8

Start up banner

During DCC, Hold and Optics Alarm

Status = MEASURE

Mirror: 50 % Peltier: 40 % COOL

tdp 0.0 ºC t 10.0 ºC

rh 49.7 % t 10.0 ºC

Y 106.00 gkg-1

t 10.0 ºC

t 10.0 ºC dV 106.00 gm -3

t 10.0 ºC (t-tdp) 10.0 ºC

t 10.0 ºC aW 0.5

OPTI-CAL Display Screens

and Navigation

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4. MAINTENANCE Routine maintenance of the OPTI-CAL is limited to the following tasks:

• Re-Filling the Water Reservoir • Desiccant Unit Replacement • Cleaning the Chilled Mirror Sensor • Re-calibration • Re-Filling the Water Reservoir.

The reservoir should be filled with distilled water only. Do not use tap or dematerialized water. The water reservoir is located on the front panel. Remove the filling port blanking cap located on the top of the water reservoir. Carefully fill the reservoir with clean distilled water to a level between the two indicator lines. Do NOT fill beyond the “MAX” indicated line, as this may cause liquid water to enter the humidity chamber and adversely effecting the control process. Replace the cap after filling. Frequency of re-filling the water reservoir is dependent on the humidities being generated, as high humidities will consume far more water than low ones. It is recommended that the reservoir level be checked on a daily basis.

4.2 Desiccant Replacement

The OPTI-CAL is supplied with a silica gel filled desiccant container to dry the air supply. It is mounted to the right hand side of the water reservoir and can be accessed by removing the clear plastic screw cap.

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The natural color of dry silica gel is orange, but as moisture is adsorbed the color will gradually change to white. OPTI-CAL tells the user that the gel will soon require replacement via a viewing port on the front of the desiccant container. When this changes color the unit will still function as normal but it is advisable to replace or recharge the silica gel at the earliest convenient opportunity. If desired, the silica gel can be regenerated by emptying it from the desiccant holder and drying it in an oven for approximately 3 hours at a temperature of between 130 to 140 ºC. Allow the silica to cool before refilling the desiccant chamber and refitting into the generator, ensuring the screw lid is correctly fitted. Frequency of desiccant/dryer unit recharge or replacement is dependent entirely upon the length of time in operation. If the chamber is used with a low RH setting, than the silica gel will not require regeneration for many weeks of operation. If the chamber is used continually at 90 % RH, then the silica gel may require regeneration after less than one week of continual operation. Typically, given a normal calibration profile and operation cycle, the OPTI-CAL can continually generate accurate and stable chamber humidity for a period of several weeks before regeneration is necessary or a replacement charge of silica gel is required. NOTE: Other desiccant materials can be used in place of silica gel, for example type 4a molecular sieve. But please note that only color change desiccant materials will alert the user to the fact that they are nearing the end of their useful operation period. It is recommend initially that the desiccant drying unit be examined on a daily basis, and then depending on the condition, increase/decrease the maintenance period accordingly. The desiccant chamber should not be removed when the instrument is in operation.

4.3 Cleaning the Optical Sensor

Throughout the life of the chilled mirror sensor, periodic cleaning of the mirror surface and optics window may be required, depending upon operational conditions and exposure of the sensor to contamination. Sensor cleaning is mandatory if the instrument indicates an optics fault. The cleaning procedure is as follows:

• Switch the instrument off, or, if it is required to leave it on, a DCC cycle must be performed. Remove the test chamber cover.

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• Clean the mirror surface and optics window with a cotton swab moistened in

distilled water. If the sensor has been exposed to oil based contamination, then use one of the following solvents: methanol, ethanol, or isopropyl alcohol.

• When cleaning is complete, replace the test chamber cover and switch the

instrument on if necessary and observe the mirror contamination value during the DCC phase. If this value is not 0 %, then remove the lid of the case and adjust the potentiometer until this value is reached, ensuring that the adjustments are made ONLY during the DCC phase. If this value is under-range the display will flash 0 %, indicating that a positive adjustment is required.

Note: there will be a delay of approx 5 seconds between the actual adjustment and the displayed value changing. 4.4 Re-Calibration The OPTI-CAL is inherently drift free by design. However, as with any high quality measuring instrument, regular re-calibration against standards is recommended. This work can only be done by exposure of the chilled mirror sensor to sample gases of known moisture content using calibrated test equipment traceable to national standards. It is recommend that the optical sensor is re-calibrated on an annual basis to ensure its accuracy. As the optical sensor is an integral part of the Humidity Calibrator this means the complete instrument is required to be returned for this work to be carried out.

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5 APPLICATION SOFTWARE The application software is an interface to the instrument to provide a display of the measured and calculated parameters, system status, charting and logging, statistical information, and a facility to view and change the system parameters.

5.1 Virtual Hygrometer

The virtual hygrometer window provides a display for the instrument by showing the measured parameters and status.

The humidity display has the ability to show dew point (°C/°F), % RH, gm-3, gkg-1, ?(t – tdp), or aw by pressing the ‘Change Units’ button. Selecting one of these options will show the measured or calculated value, but will not change the Channel1 mA output of the instrument, as this can only be done via the parameter setup window, see section 5.2. When the software is executed, it will default to the present setting of Channel1 mA output. The ambient temperature is constantly shown in the lower display.

The Mirror Condition indicates the amount of signal received back from the mirror, which includes both the level of moisture and contamination on the mirror surface. In DCC mode this display will only show the amount of mirror contamination and if greater than 80 % after a DCC, an optics alarm condition will initiate. Instrument status is shown via the five LED indicators. In DCC (initiated automatically or by the DCC Initiate button), both the DCC and Hold indicators will illuminate showing the DCC status and the hold on Channel1 mA output. When the DCC period expires, the DCC indicator will turn off leaving only the hold indicator illuminated until the system enters the measurement phase. The Fault indicator will illuminate after a DCC if cleaning of the mirror surface is required. Refer to section 4 on mirror cleaning.

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The Alarm indicator will illuminate (if selected) when the measured variable exceeds the alarm set-point. Refer to section 5.2 on parameter setup. Max Cool can be initiated by the Max Cool On button. Once initiated the Max Cool indicator will illuminate and the system will drive the heat pump into maximum depression. This feature can be used to ascertain if the measured dew point is within the measurement capability of the instrument. Pressing the Statistics button allows maximum, minimum and average values of the measured parameters to be viewed. See section 5.5 Charting and logging of the measured values can be initiated by pressing the Chart/log button. See section 5.3 The ‘Hold display in DCC mode’ check box, stops the system from updating the display during DCC when enabled. The display is held when DCC is initiated and is not updated until both DCC and Hold periods have expired.

5.2 Parameter Setup

The parameter setup window allows the setting and ranging of channel 1 and 2 mA outputs, the duration for DCC, measurement and hold, and, the values for atmospheric pressure and alarm set points.

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The Display Units and Channel1 mA Output are selected by clicking the left hand mouse button in the relevant box, which will then change the settings of both the instrument and the virtual hygrometer window. Changing the mA outputs from 4-20 mA to 0-20 mA & vice versa will change both Channel1 & Channel2 mA outputs. The maximum and minimum values of Channel1 and Channel2 Max & Min are –200 to +1000 respectively, therefore allowing the range of the outputs to be anywhere between these limits. The values for Max & Min must be integer values with a difference between them of at least 1 °C/F. If Channel1 is to be set for % RH, gm-3, gkg-1 or ?(t – tdp), then the minimum value of Channel1 Min should be 0, as a negative value for these parameters are not possible.

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The pressure value is to correct gm-3 and gkg-1 for atmospheric pressure. By entering the atmospheric pressure the display and Channel1 mA output (if either gm-3 or gkg-1 is selected) will both be corrected accordingly. The Alarm can be set to OFF or set to be active on any of the process variables i.e. dew point, ambient temperature, temperature difference, % RH, gm-3, or gkg-1 as shown above. The set-point needs to be an integer value between –200 and +1000, although negative set-points are only valid for dew point and ambient temperature. If the process variable exceeds the set-point, the Alarm indicator on the virtual hygrometer will illuminate and the Optics Fault/Alarm relay will change state. To change any of the values, enter the required value and press the return key. The background of the text box will change to yellow to indicate that the change is taking place. When confirmation has been received that the instrument has accepted the change, the background will change back to green. NOTE: When the Parameter Setup window is open, the values in the Virtual Hygrometer window are frozen. The Parameter Setup window needs to be closed for the software to resume normal display mode.

5.3 Charting and Logging

Pressing the Chart/log button on the virtual hygrometer brings up the chart / log panel window.

The chart in its default configuration displays dew point, temperature and % RH. However, gm-3, gkg-1 and ?(t – tdp), can be added by ticking the appropriate check box.

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Within the Global group box, you can select the charting and logging interval from a minimum of 5 seconds to a maximum of 1 hour. It offers the facility to log the temperature of the mirror while in DCC and Hold, or hold the measured value while in these modes and chart the held data values accordingly. To log the measured and calculated humidity values to a data file for further analysis, check the box in the Logging group box and specify a file name by pressing the Browse button. If a log file is not required simply uncheck the box. To Run, Pause and Stop the charting and logging facility, use the chart control buttons accordingly. Pressing the Run button will bring up the chart as shown below. The chart shows the measured and calculated humidity values selected in the chart group box, with an assigned identifiable color for each value. It is possible to scale, zoom and scroll both X and Y axis of the chart by using the controls in the chart settings window, which can be activated by pressing the Chart Settings button on the charting window.

The X & Y axes can be individually scaled. The X-axis can be scaled by using the ZoomX feature, while the Y-axis can be scaled by changing the min and max values, or selecting a parameter in the auto-scale list, which scales the Y-axis to the actual values of the parameter. There are a number of modes associated with the chart, which can be selected by the chart mode list; Plot, Scroll X,Y, & XY, Cursor, Zoom X,Y, & XY and Zoom Box. In order to use

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the scrolling and zooming modes, make your selection and press the left mouse button on the chart itself, moving the mouse across the chart accordingly with the left mouse button held down. This will zoom or scroll the chart accordingly. Individual data points can be selected from the chart by using the cursor mode. Select the parameter in question by clicking on a legend on the right hand side of the chart (°C dew point is shown as selected above) and moving the cursor to the point of interest; the actual value with its time stamp will be displayed above the chart.

5.4 Statistics

Pressing the Statistics button on the virtual hygrometer window will display the statistics window as shown: This shows the maximum, minimum and average of each parameter since the program began taking readings from the instrument, or since the reset button was pressed.

5.5 Control Parameters

The control parameters (protected by a password) should only be amended by trained personnel in order to adjust the system for operation in extreme conditions. Contact Kahn Technical Representation for details.

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5.6 Calibration Correction

Every OPTI-CAL is delivered with a Calibration Certificate detailing the deviation at each measurement point from a known reference value. Data provided on the Calibration Certificate is normally arranged as shown in the following extracts: Extract from a UKAS Calibration Certificate:

Test Hygrometer Generated Dew point °C

Dew point Temperature °C

Sensor Temperature °C

Correction Required °C

Expanded Uncertainty °C

-39.89 -40.11 -20 +0.22 ±0.26 -20.10 -20.31 0 +0.21 ±0.22 0.39 0.20 21 +0.19 ±0.18

Extract from a Standard Calibration Certificate:

Generated Dew point °C

Instrument Display °C

-40.1 -40.2 -20.1 -20.1 0.2 0.1

From time to time the OPTI-CAL may be calibrated by an external calibration agency, where similar data will be provided. The Calibration Correction window is a utility that allows an authorized user to input this calibration information in order to effect a real-time correction of the displayed, charted and logged data within the Opti-Soft application software. Data for dew point temperature and ambient temperature, both in units of oC, may be entered for correction purposes, along with the original calibration certificate reference number and date of calibration, providing full traceability of data. Once the correction data has been applied, by checking the box, the main Virtual Hygrometer window will indicate that corrected data is being displayed and will show the Calibration Certificate number and date. This information is also saved to the log file for data export.

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The figure on the following page shows the Calibration Correction window. Four sets of data may be entered: DP Ref: This is the dew point data for the reference hygrometer (sometimes

called the actual dew point or the standard) DP Reading: This is the measured dew point value of the OPTI-CAL under test Temp Ref: This is the temperature data from the reference thermometer Temp Reading: This is the measured temperature value of the OPTI-CAL under test Data can be entered for between 3 and 11 different dew point and temperature calibration points. If no data is inserted, no calibration correction is possible. Data should be entered with the highest dew point and temperature values at the top of the page, in descending value order to the bottom. If out-of-sequence data or spurious characters are entered, the software will raise a warning message and bad data must be re-entered. The Calibration Certificate Number field is an optional entry field and is alphanumeric. Any information entered into this field will be displayed on the main Virtual Hygrometer window when calibration correction is enabled. In addition it will be saved to the log file. Similarly, the date of calibration may be entered for display and logging when correction is enabled. Once all necessary data has been entered in the Calibration Correction window, check the Use Calibration Date to Correct Measure Values check box and then click Apply and Close to return to the main Virtual Hygrometer display. Upon the next update, the corrections entered will be applied to all displayed and logged data, and a legend above the display will indicate this fact. To remove Calibration Correction, de-select the check box and press Apply, then Close.

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NOTE: Enter the calibration data in descending order, whereby the highest values are in row 1 as shown above. 5.7 Change of Password

The initial password is “Michell”. This can be changed after entering the Control and Calibration Data windows. Selecting the Change Password menu item will display the following window, whereby you can enter a new password with up to 20 alphanumeric characters. The Password is not case sensitive.

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6. TECHNICAL SPECIFICATION

6.1 Integrated Humidity Calibrator Control Temp. range. 10 to 50 +/- 0.2 °C Range: 10 to 90 % RH Accuracy: Typically ±1 % RH, ±0.2 °C dew point, ±0.1 °C

temperature Control Temp. range: 10 – 50 +/- 0.2 °C Chamber heating rate: 1.5 °C per minute Chamber cooling rate: 0.7 °C per minute Humidity ramp rate: 3 % RH per minute Chamber size: 105 x 105 x 160 mm Measurement Units: dew point (°C/°F), % RH, temperature (°C/°F), gm-3,

gkg-1

Display: 2 x 20 character, vacuum fluorescent Resolution: 0.1 °C Outputs: analog: 4-20 mA or 0-20 mA over user settable

output accuracy ±0.2 °C. 500 ohm maximum load resistance

digital: RS232 @ 9600 baud rate alarms: volt free contact, 2 A @ 30 V DC, 0.5 A

@ 120 Vac Desiccant: Silica gel Power: 88-264 V ac 47/63 Hz, 4 A/115 V 2 A/230 V Power consumption: 60 VA. Operating temperature: +10 to +30 °C. Enclosure: Painted aluminium 520W x 290H x 420D mm Weight: 15 kg approximately.

6.2 Optical Sensor

Peltier : 2 stage. Photodetection system: Single visible red spectrum. Mirror: Gold plated copper Temperature measurement: 4 wire 100 ohm platinum resistance thermometer Sample wetted part: Acetal housing with glass optics window. Operating temperature: -40 to + 90 °C Flow velocity: 1 to 10 msec-1 Dew-Point range: -60 to +90 °C Temp range: -40 to +90 °C RH range: <0.5 to 100 %

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Depression (@ 21°C ambient): -45 °C

ºC Temperature

Chamber Set Humidity

%rh

Auto On

Manual Off

On Auto

Off Manual

Test probes

Dessicant Charge

Max.

Min.

Humidify = Yellow

D e- Humdify = Green

Heating = Yellow

Cooling = Green

Chamber Set

Communications

Display Control

OPTI-CAL Intergrated Humidty Calibrator

520 420

290

200

110

104

124

CHAMBER DIMENSIONS

Fig. 2 General Arrangement

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13 12 11 10 9 8 7 6 5

25 24 23 22

20 21

18 19

17 16 15 14 1

2 3 4

GROUND OF PC % rh CONTROL-PROBE (0-10 V) SET POINT % rh (0-10 V) 20 ºC/50 % rh IF PC = OUT (0 or 5 V,CMOS)

TEMP. CONTROL-PROBE (0-10 V) SET POINT TEMP. (0-10 V)

STATUS (0 or 5 V, CMOS) 13 12 11 10 9 8 7 6 5

25 24 23 22

20 21

18 19

17 16 15 14 1

2 3 4 USE FOR LOGGING

MAX. 100 mA/CHANNEL

25 way D Type FRONT PANEL

25 way D Type IN CHAMBER

Fig. 3 Test Probes Connections

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OPTI-CAL Integrated Humidity Calibrator · The Kahn OPTI-CAL Integrated Humidity Calibrator is a high precision, yet simple to operate, humidity calibration system designed for calibrating