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Sensit Wind Eroding Mass Sensor |
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Erosion monitoring solutions |
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October 2007:
Sensor Includes PHA Energy Output
The following link (DPC.htm) to the Sensit Data Processing and Calibration technical document has been expanded to include specific technical aspects of the new model H11-LIN sensor. Calibration data will be added as soon as it is available The information presented covers most aspects of understanding erosion data acquisition. You are free to copy, reproduce and distribute this document.
Tech Ref:
Oct 21, 2007
Backward Compatibility:
The new model H11-LIN provides the same PC and KE outputs as previous Sensit H11B & H11C sensors. It no longer provides the seldom used toggled version of these outputs.
Model H11-LIN improvements:
 | New data output: The model H11-LIN has an additional output providing the kinetic energy of every individual particle impact. This data is in the form of a variable pulse height signal. A pulse height analyzer (PHA) module to capture this data should be available by the 1st quarter 2008. |
| Programmable Gain: Sensitivity can be increased by 10X externally via data logger or by physically connecting a wire to +12V. |
| Superior seal: The crystal mounts now extends over the ends of the crystals providing a superior seal and protecting the edges. |
| Lower power: The new sensor draws less current than the previous sensors. |
| Symmetrical response: Uniform radial response has now been achieved by nickel plating the crystal surface. |
| No multiple counts: Large energy impacts do not produce multiple counts. |
Sensit PHA data requires pulse height analyzer
This applies only to the new PHA data output. The standard PC (particle count) and KE (kinetic energy) data outputs remain the same as previous models. Acquiring pulse height data requires a pulse height analyzer. The Sensit PHA output pulse may be input to any compatible pulse height analyzer for processing and collection. These units tend to be expensive and normally do not acquire a series of spectrum. Sensit plans to produce a PHA module by the 1st quarter 2008 that will process and record up to 1000 spectrum each comprised of 256 channels of 16 bit counters.
Background A pulse height analyzer (PHA) produces a graphical representation of the spectrum of pulse heights. Units of time are not applicable. The x-axis represents pulse height and the y-axis is the number of counts at that pulse height. The longer a PHA is allowed to acquire data, the greater the resolution of information. For example; A peak will become increasingly defined.
The PHA is most commonly used in the field of nuclear scintillation. It is simply the counting and sizing of radioactive particle energy. The energy spectrum of radioactive atomic particles clearly defines a radioactive isotope by "signature" peaks.
Generic PHA instrument structure
A pulse height analyzer is an instrument with a large number of counters. The number of counters typically vary from 128 to 4095 or more. Each counter is assigned to a small pulse height (voltage) range. Each counter is typically capable of counting 216 -> 220 counts per channel (counter). Example: If the PHA input voltage range for incoming pulse heights is 4.095 volts, and there are 4095 counters, a separate counter is assigned to count pulse heights over every 1mV portion of the 4.095 Volt range.
Sensit PHA data
The amplitude of each Sensit PHA output pulse is proportional to the energy transferred from one particle impact. A pulse height analyzer data acquisition module is being developed to acquire the large amount of data produced.
Sensit expects to have a PHA module available 1st quarter 2008. Alternatively, if your facility is technically inclined, you could build your own pulse height analyzer. The standard Sensit PC output pulse can be used as a sync pulse for your PHA. All you need to do is build a PHA performing an A/D conversion of the Sensit PHA output (0->4.095 Volts) within 40uS after the rising edge of the PC output. Your A/D resolution (8, 10, 20 bit A/D) determines the number of counters your memory must support. Use this A/D value to address a memory location where you read the value in that address, add one to it, and put it back. Thats all there is to it, except for dumping the memory via RS232 or USB into your computer. They are really quite simply in their elementary form.
Gain Selection
Note: The dynamic range of the pulse height output covers fine to medium particle impact energies encountered during typical erosion events. The total dynamic range (105) of all possible eroding particle energies is too great to be covered by a single linear A/D system so we incorporated the selectable gain (X1, X10) to increase the sensors capability.
Model H11-LIN eroding mass sensor
Dimensions:
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Base diameter: 2.050, length: 8.00 +/- 0.250 |
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Upper post diameter: 1.050 length: 5.50 +/- 0.50 |
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Crystal diameter: 0.915 length: 0.475 +/- 0.20 |
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Top of base to center of crystal: length: 3.100 +/- 0.050 |
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Cable diameter: 0.210 length: 25 feet. |
Outputs:
| Particle count (PC) data output is a CMOS/TTL compatible pulse indicating one particle impact, |
| Kinetic energy (KE) is a CMOS/TTL compatible pulse representing a fixed amount of energy that has impacted the sensor. Each pulse is always represents the same amount of total energy and is calibrated by normalizing it to the mass caught by a field catcher. A lab calibration has virtually no values because there is extreme variance due to mean particle density, spin and modulus of rupture for aggregates. The catcher mass normalization method compensates for a multitude of variables including day to day environmental effects such as rain, humidity, radiation etc. |
| NEW: Pulse height analysis (PHA) output is a pulse varying in amplitude with individual particle impacting energy. Pulse width: ~50uS, amplitude: 0 -> 4.8V. When input to a pulse height analyzer the PC output can be used as the sync if required. A PHA module should be available 1st quarter 2008. Due to the extensive amount of data, this data will be output serially via RS232. |
Inputs:
| +12VDC@70ma |
| Gain select (1X, 10X) can be selected via data logger output (open collector w/<10K pull up resistor). Gain also be selected by connecting this wire to ground (1X) or connected to +12V (10X). |
Model H11-LIN Wiring Color Code
New model number -
H11-LIN
Outputs
| (brown) KE (kinetic energy - pseudo mass flux) - CMOS/TTL compatible pulse |
| (white) PC (particle counts) - CMOS/TTL compatible pulse |
| (blue) PHA (particle energy) - variable pulse height |
Input
| (green) GAIN - Gnd(1X), +12VDC(10X). |
Power
| (red) Power + 12VDC @ 70ma/85ma (1X,10X mode) |
| (black) Ground |
Earlier models - H11B or C
(Replaced by Model H11-LIN)
Outputs
| (brown) KE (mass) - pulse |
| (white) PC (particle counts) - pulse |
Alternate outputs (seldom used)
| (green) KE (mass) - variable pulse width |
| (blue) PC (particle counts) -variable pulse width |
Power
| (red) Power + 12VDC @ 90ma |
| (black) Ground |