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laser temperature deviates by more than 20% from its set point, the laser
current cannot be enabled. Also, the set points for the laser current and
temperature are locked. Changing these parameters could cause
significant degradation in the performance of the instrument.

Reference

: reads the laser reference voltage from the monitor photodiode.

Scatter

: reads the background DC molecular scatter level from the APD.

This should read around 0.200 V to 0.250 V when the pump laser is on.

Auxillary

: not used.

Configuration

Tab:

This tab holds all the instrument configuration parameters and reads some
housekeeping values.

Save

: saves present instrument configuration to file. Will prompt for file

name.

Load

: loads saved instrument configuration file. Will prompt for file

name. The factory provided config file is called DMTSNxxCAL and
should not be overwritten. Choose a new file name for config files with
adjusted parameters.

Pulse width

: for each of the gain stages (G0,G1,G2,G3) this control sets a

window for acceptable particle pulse widths. A particle pulse must be

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Содержание UHSAS-0.055

Страница 1: ...060405DMT doc 1 34 Ultra High Sensitivity Aerosol Spectrometer DMT Model UHSAS 0 055 0 055 1 0 microns Manual Droplet Measurement Technologies 5710 Flatiron Parkway Suite B Boulder CO 80301 USA Telephone 303 440 5576 ...

Страница 2: ... of procedures other than specified in this manual may result in hazardous radiation exposure This label is displayed on the top cover front and back of the instrument This label is located on the support structure underneath the instrument cover near the laser interlocks to serve as a warning if the instrument cover is removed This label is located on the optical block and the arrow points to the...

Страница 3: ...The power cable keyboard and mouse for the instrument are located in a pouch in the lid of the case The instrument will be shipped with a cap on the inlet Remove this cap before the initial startup Install sample line 1 8 OD Tygon tubing and zero filter Connect the keyboard trackpad to a USB port on the front panel The USB ports are located just below the floppy CD combo drive Before connecting th...

Страница 4: ...airflow setting 700 SCCM Maximum count rate 3000 per second Counting efficiency at least 50 at min size increasing to 100 Number of channels 100 Minimum detectable size 0 055 microns Size range 0 055 1 0 micron Environmental 10 to 30C Sea level to 4 km altitude RH non condensing Dimensions 56 x 43 x 24 cm Weight 31kg Power requirements 100 240VAC 47 63Hz BUSS fuse GMA 2A ...

Страница 5: ...UhsasManualRevE060405DMT doc 5 34 Insert unit specific checklist here UHSAS 55nm 1000nm QC Checklist ...

Страница 6: ...is shortcut This will bring up the UHSAS window on the desktop LabView 7 1 is a software program from National Instruments which provides a user friendly virtual instrument commonly called a vi panel for the control data display and data logging of the UHSAS instrument The UHSAS vi controls the instrument through a series of vi displays for various instrument functions Examples of this display are...

Страница 7: ...unts versus channel number You need to select push the Run button near the upper left corner of this window to show the particle accumulations This should have very few counts if the zero filter is in place Remove the zero filter for room air sampling and many counts will appear ...

Страница 8: ...ntrolled through the Map tab Select the Map tab to change control the size range displayed The Map tab shows the boundaries of the bin width map that is used for the display The map can be modified in multiple ways depending on user preference See Chapter 6 of the manual for details ...

Страница 9: ... Record button will change color from a darker grayish appearance to the same color grey as the background Press the rectangular STOP button located towards the upper right portion of the UHSAS screen This stops the execution of the UHSAS vi Next the computer must be shut down using normal Windows2000 controls and the on off switch located on the rear panel of the instrument ...

Страница 10: ...e sample aerosol through the optical interaction region including flow control and measurement 3 the analog electronics system for amplifying and processing the particle signals 4 the digital electronics system for analyzing particle signals binning signals according to user specified bin mappings and generating a histogram of number of particles in the specified bins and for communicating with th...

Страница 11: ...onsists of two pairs of mangin collection optics capable of collecting light over a large solid angle The mangins image the volume of space at which the flow intersects the laser mode onto a photodiode There are two pairs of collecting optics one pair images onto an APD for detecting the smallest particles the primary scattering detection system The other pair located on the opposite side of the b...

Страница 12: ... mode High reflector Sheath inlet Sample inlet Imaging optics photodiode pump Jet assembly Exhaust jet Pump laser Imaging optics Secondary scattering PIN photodiode block Laser crystal Laser mode High reflector Imaging optics Jet assembly Pump laser High reflector Primary scattering Avalanche photodiode Laser output reference photodiode ...

Страница 13: ...etween 1 and 100 sccm and the sheath flow is typically 700 sccm Particle velocity depends on sheath flow rate but is on the order of 50 to 100 m s The particles are confined to a region of space whose extent is approximately 10 to 20 of the laser beam diameter which is 0 5 mm e 2 intensity diameter This yields a sizing resolution of approximately 2 to 5 of the particle size See Figure PUMP Mass fl...

Страница 14: ...ratios The G2 G1 ratio is more complicated since it involves two independent photodetectors with independent electronics and on opposite sides of the optical block See the discussion in the Calibration section The gain stages also provide low pass filtering to the signal Each gain stage then feeds it s own baseline restoration circuit which restores the 0 Volt baseline which is disturbed by freque...

Страница 15: ... delay to allow the particle signal to reach its maximum the 4 ADCs sample the 4 peak held particle signals from the four gain stages Starting from highest gain G3 and working down in gain the first ADC that is not in saturation is the valid particle ADC The value of this ADC is read and compared to a look up table of bin boundaries previously loaded into memory Depending on where in the look up t...

Страница 16: ...d a 30Gb hard drive The monitor is a standard LCD display built into the front panel of the instrument All normal OS operations are handled by Windows e g networking file management printing etc The user interface is a virtual instrument written in LabView 7 1 See VI section Communication with the digital electronics system is via internal RS232 115 200 baud 8N1 The update rate of the PC I O is co...

Страница 17: ...us the particle size in nm from calibration standards Once the relative gains are known the corrected response for the entire instrument can be formed Since the wavelength of the instrument is 1054 nm it is expected that all particles below approximately 200 300 nm will lie on a sixth power curve that is the particle signal is a sixth power of the particle size This has been hard coded into the in...

Страница 18: ...n of the calibration curve from the preset may be required in order to accommodate several possible inconsistencies for example particles that have been inconsistently sized with other methods nonlinearities in the instrument s detection electronics or improved empirical data on the non power law portion of the curve One comment on the relative gains is needed In the particle size regions where de...

Страница 19: ...n may be needed see below Particle size recalibration It may be necessary to recalibrate the size scale of the UHSAS Some reasons for this include 1 the laser power has drooped and cannot be fully restored 2 internal relative calibration has degraded 3 other types of particles not PSL with a different index of refraction will be used 4 to assure agreement with previously used standard materials Th...

Страница 20: ... move the curve up and down appropriately to convert voltage on various gain stages to particle size There are two white points fixed by the instrument one at 10 nm and one at 300 nm These are used only to define the region of the instrument described by a power law curve They are not absolute reference points they are used only for forward and backward extrapolation of the curve from the real cal...

Страница 21: ...he calibration curve will take effect on the next bin map commit Flow rate calibration confirmation In order to confirm calibration of the UHSAS instrument flow meters the following steps should be taken 1 Sheath and purge flow will not need calibration as their exact values are not critical Sheath should be set to 700 sccm with the manual valve purge valve should be closed 2 Sample flow is calibr...

Страница 22: ...Laser Controls Step 3 Turn the laser current on see Laser Controls Step 4 wait a few minutes for warm up Step 5 confirm that the scatter is appropriate see Laser Controls Step 6 Confirm that the sample flow is on and set as desired see Flow Controls Step 7 Calibrate if necessary see Calibration Step 8 Commit the desired bin map see Map Step 9 Set histogram parameters as desired see Histogram Step ...

Страница 23: ...f the gain stage chosen Specify the range minimum and maximum values Choose the number of bins Choose a linear or logarithmic bin spacing to create the bin map Bin map appears in the bin table individual bins can be edited like a spreadsheet Press Commit wait for commit bar to complete This process downloads the bin map to the histogram microprocessors Null loads nulls into the bin map Read reads ...

Страница 24: ...exceeds the set point the histogram stops running the display holds and the record file completes If forever is selected the instrument cycles indefinitely showing the present cycle number Accumulation time Accumulation time sets the length of time over which counts will be accumulated At the end of the set time the histogram data will be written to the record file if enabled and the histogram wil...

Страница 25: ...Controls Tab Sample Set sets the sample flow sccm Sample Act reads the actual sample flow sccm Sheath reads the sheath flow sccm Should be 600 800 sccm Purge reads the purge flow sccm Laser current sets the pump laser current A The lower display box is the actual current The set point and actual should be close but not the same Toggle ON OFF to turn the laser current on or off Laser temp sets the ...

Страница 26: ...D This should read around 0 200 V to 0 250 V when the pump laser is on Auxillary not used Configuration Tab This tab holds all the instrument configuration parameters and reads some housekeeping values Save saves present instrument configuration to file Will prompt for file name Load loads saved instrument configuration file Will prompt for file name The factory provided config file is called DMTS...

Страница 27: ...in For example the trigger threshold might be set to 0 100 V with this signal size representing a 55 nm particle The user can select a lowest bin of 60 nm so that some triggers particles between 55 and 60 nm will not appear as counts they will appear in the underflow bin if selected Or the user could select a lowest bin of 50 to 54 9 nm No counts will appear in this bin since the trigger threshold...

Страница 28: ...tage on which the particle signal appears mV the signal size in mV of the particle signal and nm the size of the particle in nm At least one point needs to be specified to calibrate the unit This is normally the NIST 100 nm SRM which appears as 4000 mV on G3 Any number of reference particles can be used to calibrate the instrument The cal curve will be interpolated between reference points in log ...

Страница 29: ...n gain stages This is accomplished by running ambient air through the instrument and pressing CLEAR and then RUN on each of the relative gain tabs Particles whose signals appear on two adjacent gain stages this is the overlap region of the gain stages will be measured and recorded The relative gain graph will show the gain and offset calculated from these points This gain and offset along with the...

Страница 30: ...f this screen You will be prompted for a filename and location The recorded file is a comma delimited ascii text file which contains time housekeeping parameters and data from each of the 100 channels accumulated over the interval set on the Histogram screen This data can be read directly into spreadsheets for processing Each time the Record button is pressed a new file is written but you can appe...

Страница 31: ... has a leak or it is counting noise Noise will typically appear in only the first few channels if the unit has a leak typically there will be an ambient looking distribution o If the unit appears to have a leak check any external connections between the unit and the filter and rerun test o If unit appears to have noise counts Check the reference and Scatter level clean optics if necessary o If acc...

Страница 32: ...install cleaning port and tighten thumbscrews ensure o ring is installed Repeat above 3 steps for other optic Turn pump back on Reinstall cover on the unit do not install screws into cover until power has been rechecked in case unit requires more cleaning Turn on the laser current Let instrument run for 15 minutes to stabilize Check the Scatter and Reference levels of the unit If they are within 1...

Страница 33: ... data collection by an external data system is also available through the back panel This data stream is ascii text at 115200 baud 8N1 tab delimited and is transmitted at the rate set on the Configuration tab under Update Rate Hz The format is given in the first 2 lines of the data file The serial port connector is a standard 9pin D connector and can be connected to the serial port of an external ...

Страница 34: ...UhsasManualRevE060405DMT doc 34 34 Appendix A Interconnect Wiring Drawings Appendix B Schematics Assembly Drawings and CVS s Appendix C Cables Appendix D Bill of Materials ...

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