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DMT UHSAS-0.055 Manual

Ultra high sensitivity aerosol 0.055 - 1.0 microns
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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
UhsasManualRevE060405DMT.doc,1 / 34

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  • Page 1 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 Telephone 303-440-5576 UhsasManualRevE060405DMT.doc,1 / 34...
  • Page 2 Laser Safety Warnings STRICT OBSERVANCE OF THE FOLLOWING WARNING LABELS IS ADVISED This instrument is a Class I laser product. CAUTION: Use of control or adjustments or performance of procedures other than specified in this manual may result in hazardous radiation exposure.

  • Page 3: Chapter One - Unpacking & Cabling

    Chapter One - Unpacking & Cabling The UHSAS instrument is delivered in a shipping case which also contains the necessary cables etc to make the instrument functional. Remove the instrument from the case by putting your hands in the small cutouts on each of the long sides of the instrument. The handles for the instrument are located in these cutouts.

  • Page 4: Chapter Two - Specifications & Qc Checklist

    Chapter Two - Specifications & QC checklist Laser Type solid state pumped Nd :YLF Sample flow 10-100 SCCM (this unit) 1-10 SCCM optional Sheath airflow setting 700 SCCM Maximum count rate 3000 per second Counting efficiency at least 50% at min. size increasing to 100% Number of channels Minimum detectable size...
  • Page 5 Insert unit specific checklist here UHSAS 55nm-1000nm QC Checklist UhsasManualRevE060405DMT.doc,5 / 34...

  • Page 6: Chapter Three - Getting Started & Shutdown/Power Off Procedure

    Chapter Three - Getting Started & Shutdown/Power off procedure The UHSAS instrument contains a computer which runs the Windows2000 operating system. It is assumed that the instrument user is familiar with the normal operation of this operating system on a computer. Before starting the instrument, ensure that the keyboard/trackpad are connected to the USB port on the front panel of the instrument, that the zero filter is in place on the inlet, that the power switch is in the off position, and the power cable is connected.
  • Page 7 Next, select the Histogram tab to display counts 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.
  • Page 8 The size range displayed on the histogram is controlled 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.
  • Page 9 Shutdown / Power off procedure -Put zero filter on inlet line. -If file recording is activated, go to Histogram tab and press the Record button. The Record button will change color from a darker grayish appearance to the same color grey as the background.

  • Page 10: Chapter 4 - Theory Of Operations

    Chapter 4 - Theory of operations Instrument subsystems The UHSAS is an optical-scattering, laser-based aerosol particle spectrometer system for accurately and precisely sizing particles in the range from 0.055 µm to 1.0 µm diameter. It uses fully user-specified size binning of up to 100 channels anywhere within its size range.
  • Page 11 The Optical system consists of a) the laser and associated components and optics, b) the detection system, including collection optics, photodetectors, and reference monitoring c) mechanical housing for above a) The laser is a semiconductor-diode-pumped Nd :YLF solid-state laser. It operates in the fundamental (TEM ) spatial mode on a 1054 nm laser line with an intracavity power of ~1 kW.
  • Page 12 Sample assembly inlet side view Sheath inlet Laser mode photodiode High Laser reflector Pump laser crystal Imaging optics block Exhaust jet pump Figure: Side view of optical block Secondary scattering (PIN Imaging optics photodiode) High Laser reflector assembly output Laser mode reference photodiode Imaging...
  • Page 13 2) flow system The mechanical laser mount forms a sealed block around the laser and the inlet/exhaust jets. A pump draws on an exhaust jet pulling flow through the inlet jet and across the laser mode. The inlet jet is an aerodynamically focused assembly with a sample nozzle of 500 µm diameter and a sheath nozzle of 760 µm diameter.
  • Page 14 3) Analog electronics. The analog chain converts the photocurrent of the detector photodiodes to a voltage and processes that signal (called the particle signal). The chain is repeated for the primary and secondary detection systems. After the photodiode transimpedence amplifier, the photo signal is mixed with a signal derived from the reference detection system for noise cancellation.
  • Page 15 Figure. Block diagram of analog electronics 4) Digital electronics system a) ADCs and peak height analysis For each of the four gain stages (2 primary, 2 secondary) there is an associated Analog- to-digital converter. The ADCs run a 16-bit conversion at 100 kHz sample rate. The chain of events is begun as a particle traverses the laser mode and begins scattering light.
  • Page 16 relative gains and calibration points into a mapping of voltages at each of the gain stages. The mapping process is transparent to the user and occurs every time a bin map is committed to the instrument. (See the calibration section below.) b) monitoring/control The digital system also provides monitoring and control of onboard systems.
  • Page 17 particle might be 3 V on G3 and 0.060 V on G2.) By noting many such events, a relationship between the signal size of a particle on the two gain stages can be determined---the relative gain. A linear fit to the data for many events produces a relative gain and an offset between adjacent gain stages.
  • Page 18 In principle, if all the relative gains are known accurately, and the calibration curve is known, the instrument need only be calibrated in an absolute sense at one point---any point in fact. In practice it is best to use a trusted particle or a few trusted particles. For factory calibration, the NIST SRM 1963 100 nm standard reference material is used to fix the calibration at one point--- and thereby with the relative gains and calibration curve, calibrate the instrument over its range.
  • Page 19 Chapter 5 - Acceptance/Performance Checks Particle size calibration confirmation In order to confirm calibration of the UHSAS instrument, the following steps should be taken. 1) The instrument’s primary calibration is to PSL standard reference materials from NIST: the NIST 100 nm SRM and the NIST 269 nm SRM. Other manufacturer’s particles may or may not agree with the sizes reported by NIST and therefore in general cannot be used to confirm the factory calibration with high accuracy.
  • Page 20 reached. The process will stop when the preset number of points has been acquired. The graph should show the data points scattered around a best-fit line. Repeat this procedure for the other relative gain tabs (labeled “G2:G1 Gain” and “G1:G0 Gain”). Acquiring a sufficient number of large particles (for G1:G0) may take a significant amount of time (1- 10 minutes), especially at flow rates below 60 sccm.
  • Page 21 The parameters are fit parameters to 3 order polynomials used to describe the response of the flow controller. The parameters can be changed to accommodate other gases, etc. Consult DMT for instructions or revised calibration parameters.
  • Page 22 Chapter 6 - Short Guide to UHSAS User Interface (vi) In this section: indicates a TAB title Blue indicates a BUTTON title Green indicates a SLIDER or INDICATOR or TEXT control title Orange indicates an area of grouped controls To Start: Step 1: run the vi by pressing the arrow in the LabView toolbar.
  • Page 23 This tab sets and commits a bin map (the x-axis of the histogram graph). The sliders at the top of the page are shortcuts for filling the bin map spreadsheet. The bin map spreadsheet values are the values that are committed to the instrument.
  • Page 24 bin and above. Note that the total number of channels allowed is 100 including the underflow and/or overflow bins. Histogram Tab: This tab displays histograms, sets integration times and initiates data logging. Accumulation count: Accumulation count sets the number of cycles of accumulation time to be performed.
  • Page 25 Cumm: puts the histogram in cumulative mode. Does not affect record data. Cummulative mode can be entered or left while a histogram is stopped or running. Histogram graph is set to autoscale the x and y axes. For fixed axes, right click in the graph, uncheck autoscale.
  • Page 26 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.
  • Page 27 between these two times for it to be counted. It is specified approximately in microseconds. Difference: not used. Pressure: reads the ambient pressure in kPa. Temperature: reads the case temperature in K. port: should be set to COM1 Trigger Threshold: this is a very important and somewhat subtle parameter.
  • Page 28 This tab performs the calibration functions of the instrument. (See also the Particle Size Calibration section of this manual.) There are subtabs on this page: Calibration Curve subTab: This tab shows the calibration curve for the instrument. The signal sizes (in mV) are converted into voltage as they would appear on the highest gain stage (G3).
  • Page 29 (G0). The diameters specified are absolute in nm, and the signal size is specified as a relative number. This is the only gain stage that can be set to something other than a 6 power law. The easiest way to enter many G0 points is to directly edit the configuration file.
  • Page 30 This tab allows a “Service” user to input or reset passwords for the “Calibration” and/or “Service” user. Data logging is controlled through the Histogram screen. To record data to the hard drive, press the Record button on the left side of this screen. You will be prompted for a filename and location.
  • Page 31 Chapter 7 - Safety Procedures and Troubleshooting Safety Procedures CAUTION, do not operate laser with instrument cover off. This unit is equipped with a Laser safety interlock system. Whenever the cover is removed, 2 mechanical switches are activated. 1 turns off the AC power to the laser control module that supplies power to the laser.
  • Page 32 • Turn off the pump by using its toggle switch, which is mounted to the top of the pump. o Note: Whenever pump is turned off , the Sample set flow should be turned down to zero to keep the mass flow controller operating within manufacturer’s specifications.

  • Page 33: Chapter 8 - Communications

    Chapter 8 - Communications Most communication for the UHSAS instrument will be through the Ethernet network connection. See your IT support department for assistance with connecting the UHSAS to the network. A serial port for data collection by an external data system is also available through the back panel.
  • Page 34 Appendix A. Interconnect Wiring Drawings Appendix B - Schematics, Assembly Drawings and CVS’s Appendix C - Cables Appendix D - Bill of Materials UhsasManualRevE060405DMT.doc,34 / 34...