Short Name: 
UHSAS
HAIS Instrument: 
No
Deployments: 
WE-CAN
SOCRATES
ARISTO 2016
ORCAS
CSET
WINTER
FRAPPE
DEEPWAVE
CONTRAST
NOMADSS
SAANGRIA_TEST
DC3
TORERO
IDEAS-4_C130
HIPPO-5
ICE-T
HIPPO 4
DC-3 TEST
WAMO/ICARE
PREDICT
HIPPO 3
HIPPO 2
ADELE-SPRITE
HIPPO 1
START08
HEFT08 / GISMOS
ICE-L
PACDEX
Date Acquired: 
March, 2007
Property Tag and/or Serial Number: 
S/N 001
Current Location: 
Aerosol Lab
Operational Status: 
requestable, ready for deployment
Inventory Count: 
1
Problems - Documentation: 

Incomplete, lacking maintenance manual (cleaning and aligning optics, checking electrical circuit operation, diagnostic interpretation of measurements, troubleshooting guide)

Lead Contact: 
Mike Reeves
Model: 
DMT UHSAS-A (airborne)
Alternate Contact: 
Jorgen Jensen
Measurements Provided: 
Aerosol size distribution and concentration, 60 - 1000 nm diameter
Typical Sampling Rates: 
10 Hz
General Description: 
  • Photo of the UHSAS (top instrument) mounted next to a 2DC probe (bottom) on the GV research aircraft:
  • The UHSAS, originally manufactured by Particle Metrics, Inc. and now by Droplet Measurement Technologies, measures the concentration and size distribution of aerosol particles having diameters from 0.060 --1.0 µm, in 100 bins that are approximately logarithmically spaced. The instrument flies in an under-wing canister and senses particles in the airstream via light scattering from individual particles. The maximum counting rate for which coincidence error may be neglected is about 3000/s, so the maximum concentration (at a sample rate of about 0.83 volume cm3/s) is about 3600 cm-3.  Flow control is via a volumetric flow controller, and concentrations are reported in the data files at ambient (not instrument) conditions. Data are transferred via RS-422 to the aircraft data system and recorded there, and are optinally recorded on the laptop as well.

  • The specifications for the instrument limit its operation to > -40°C and < 12 km altitude, and there have been some operational problems at higher altitude and lower temperature, notably noise in the first channels or anomalously low measurements of concentration. These have been improved, but not eliminated, through modifications to the instrument.  Small-diameter noise in particular continues to be a problem.  The probe covers the full size range through the use of two different detectors, each having two gain circuits, and there is some overlap among the sensitive regions of these four channels so the instrument must choose the best signal for each size pulse. The ranges change somewhat during flight, so at times gaps or discontinuities develop in the size distributions. This also has been addressed in recent changes and is expected to be of less concern in projects beyond 2012.

  • The UHSAS must receive an initialization record, which can come from a host laptop PC with a LabView application, or from a static record sent by a Data System Module (DSM). The instrument fits in a standard 6" instrument wing pod.

Measurement Characteristics: 

See the 'Documentation' link at right.

Calibration Methods: 

Particle size - use monodisperse aerosol particles, typically PSL or any aerosol source with DMA system

Air flow rate - Gilibrator

Pressure - use RAF standard

History of Significant Changes: 
  • 2007, DMT:  Refit detector that was rubbing inside of canister.
  • 2010 March, DMT:  Maintenance; change gain stage resistors to improve overlap regions, change amplifiers to reduce temperature sensitivity.
  • 2010 Sep during PREDICT, RAF:  Add tube to inlet needle, avoiding cloud particle interference.
  • 2010, RAF:  Rearrange data I/O serial so that laptop can re-calibrate gain overlaps during flight.
  • 2010, RAF:  Instead of DSM, laptop provides startup record to probe.
  • 2011 April, RAF:  Move pressure sensor to measure within aerosol stream instead of canister interior.
  • 2014 April, DMT:  Optics block rebuild.
  • 2014 Oct., RAF: Corrected flow processing algorithm to properly treat sample flow as volumetric (had been assumed mass flow since acquiring the probe).
  • 2015 April, RAF: Convert from RS-232 communication to RS-422 (probe-->laptop & ADS).
  • 2015 May, RAF: Move optics block heater circuit from 28 VDC to 115 VAC, 60 Hz. Installed a 28V power block for this.
  • 2015 Nov., DMT: Replace pump laser and Nd:YLF crystal.

A differential size distribution from an ARISTO-2016 flight:

 

Two differential size distributions from a WE-CAN flight: