Technical -  (Last update April 2008) Also see the H11-LIN -> SPECIFICATIONS DOCUMENT: DPC.pdf

Technical - (Last update February 2009) Useful technical notes, perform your own threshold calibrations:  Technotes.htm

Technical - (Last update February 2009) Sensit(tm) sensors are now shipped with particle impact threshold calibrations for 1X and 10X gain selections in Dyne-cm.  Also, radial response calibrations for both particle impact (PC) and kinetic energy (KE) outputs. These calibrations are graphically shown as polar graphs with tables of suggested corrections factors for both.  This compensated for unavoidable irregularities in the crystals.

Sensor specifications  (July 21, 2008)

¹ PHA – Variable height pulse, 50uS, analyzer output for energy per particle.  The new pulse height analyzer (PHA) data output is an additional output for future use. It will become useful when a PHA module becomes available.

² PHA output is a variable pulse height; all others are digital TTL/CMOS compatible.

³ LT - Long term studies.

The current model is the Model H11-LN. A new PHA  data output and selectable gain is now standard.  Particle count sensitivity has been dramatically increased over previous models.  The circuit boards are now conformal coated virtually eliminating corrosion failure. The coated boards are also incased in solid RTV(tm) potting rubber.

The cylindrical crystal is suspended between rubber mounts axially on a 2.54cm diameter stainless steel post.  The previous anodized shield that was glued on to the outer surface of the crystal has been eliminated.  The crystal surface is now nickel plated protecting it from impact damage and most importantly insures symmetrical radial response.

These sensors are designed to be completely wiring error safe. This means any wiring hookup errors caused by connecting any combination of wires of any polarity to 12VDC will not causing damage to the sensor electronics.  There are also 8 each, 20amp (100amp pulse) internal static lightning arrestors to protect against static charges produced by saltating particles and near lightning strikes.

The outputs are 1)number of particle impacts (or "PC", particle count), and 2)kinetic energy (KE) are CMOS/TTL compatible pulses and, 3) the new PHA (pulse height analysis) output is a variable pulse height intended for future use. See for more info.

A field data system with pulse counting capability is required to record PC & KE data outputs.  These data outputs are TTL/CMOS compatible Q (positive polarity) pulses.

The Particle Count output is straight forward. The KE pulse represents a fixed amount of kinetic energy.  This output has been empirically found to correlate to mass flux with a linearity r^2 => 0.997.

The following document has not been updated to include the new additional PHA data output and covers 90% of all technical issues. Please read the document for a detailed description of erosion site requirements and data acquisition.

The new model H11-LIN

Outputs:

Inputs:

Earlier Model Number  - H11B  Wiring Hookup

NOTE:  New color code as of November 2006

The reason for the wire color change;  We used to use cable which had two large diameter wires and four small diameter wires. This forced the power (+12VDC and Ground) to be naturally be assigned to the larger diameter wires.  Unfortunately, these colors were black and white.  Now that all wires are the same diameter (and same color selection) we decided we must adhere to the conventional colors of red and black for power.

Outputs

Alternate outputs (seldom used)

Power

Original Model  - H11B - Standard Wiring Hookup

NOTE:  Original color code prior to November 2006

Outputs

Alternate outputs (seldom used)

Power

Data Processing and Calibration document - Main reference manual

The "Data Processing and Calibration" document contains theory of operation, catcher information and technical information about the wind eroding mass sensor.

Lab  Response Symmetry Calibration - December 2008

It is my greatest fear that many users will the symmetry response pattern as a severely negative aspect of the sensor's characteristics. I chose however to present these findings as mere factual information of detail rather than some a deficiency. 

Independent symmetry tests have been performed and published characterizing other available saltation sensors with far superior symmetry and sensitivity results for the Sensit (TM) erosion sensor.

The radial response calibrator shown below uses a standard sensor piezoelectric crystal as a kinetic energy source providing matched mechanical coupling characteristics. A stepper motor provides positioning for data down to one degree increments perpendicular to the crystal surface.

IMPORTANT NOTE: A radial symmetry response calibration has virtually no influence on the particle counts (PC) output, i.e. number of particle impacts. Particle counts, by nature has only the values of 1 or 0, either yes an impact (which is one count) or no impact.  The calibrator's impacting energy is far less than 99% of the impacting energies commonly encountered during natural saltation events. The symmetry pattern can have up to a 10% effect on threshold of movement energies where the energies may be near zero.

The response symmetry does however effects the kinetic energy (KE) output (commonly used as mass flux) because the derivation of total integrated impacting energy is an analog value.

Data below is averaged to emulate the natural averaging of particles impacting the sector facing the wind. The wide natural angle of exposure in the wind helps smooth the otherwise rather rough characteristic response.  Raw one degree raw data exhibits scatter due to small changes electrode coating thickness and internal characteristics of clay from which the crystal is made.

Above is an actual (10 degree/dpt) radial symmetry calibration showing an example of an exceptionally good response pattern for the new Model H11-LIN sensor.  The response pattern varies substantially with irregularities in the crystal. The crystal manufactured causes are variance of the charge  in the ceramics, thickness variance of the silver paint used as the electrode interface.  We have no control over this and because they are expensive and difficult to get it is too expensive to select only the best response curves.  I wish selection of best response curves were possible.

The 10 degree intervals have been averaged over a 120 degree band per data point and shown at the midpoint.  This test requires the PHA output standard on the new Model H11-LIN sensor and can not easily be performed on earlier models.