LabVIEW TM Research Articles

A compact flow injection analysis system for surface mapping of phosphate in marine waters

The design, construction and validation of a compact, portable flow injection analysis (FIA) instrument for underway analysis of phosphate in marine waters is described. This portable system employs gas pressure for reagent propulsion and computer controlled miniature solenoid valves for precise injection of multiple reagents into a flowing stream of filtered sample. A multi-reflection flow cell with a solid state LED photometer is used to detect filterable reactive phosphate (0.2 μm) as phosphomolybdenum blue. All the components are computer controlled using software developed using the Lab view™ graphical programming language. The system has the capacity for sample throughput of up to 380 phosphate analyses per hour, but in the mode described here was operated at 225 analyses per hour. Under these conditions, the system exhibited a detection limit of 0.15 μM, reproducibility of 1.95 % RSD ( n=9) and a linear response ( r 2=0.9992) when calibrated in the field with standards in the range 0.81–3.23 μM. The system was evaluated for the mapping of phosphate concentrations in Port Phillip Bay, south eastern Australia, and during the course of a 150 km cruise, 542 analyses were performed automatically. In general, good agreement was observed between analyses obtained using the portable FIA system and those obtained from manual sampling and laboratory analysis.

Portable triple silicon detector telescope spectrometer for skin dosimetry

The features of a newly developed portable beta telescope spectrometer are described. The detector probe uses three silicon detectors with the thickness: 50 μm/150 μm/7000 μm covered by a 2 μm thick titanium window. Rejection of photon contributions from mixed beta/photon exposures is achieved by coincidence requirements between the detector signals. The silicon detectors, together with cooling aggregate, bias supplies, preamplifiers and charge generation for calibration are contained in a handy detector probe. Through a 3- or 10-m cable the detector unit is connected to a compact, portable processing unit including a laptop computer executing control, monitor, histogram and display tasks. The use of digital signal processing at an early stage of the signal chain has facilitated the achievement of a compact, low-weight device. 256 channels are available for each of the three detectors. The LabVIEW TM software distributed by National Instruments was used for all program developments for the spectrometer, comprising also the capability of evaluating the absorbed dose rates from the measured beta spectra. The report describes the capability of the telescope spectrometer to measure beta and photon spectra as well as beta dose rates in mixed beta/photon radiation fields. It also describes the main features of the digital signal-processing electronics.

Dual parameter analysis of CsI:Tl/PMT with a digital oscilloscope

Abstract Scintillation pulses from alpha-particle and gamma-ray excited CsI:Tl were recorded with a photomultiplier tube and digital oscilloscope card in single parameter (pulse shape or pulse height) and dual parameter (simultaneous pulse shape and pulse height) modes. A 2.8×1.3×1.3 cm 3 CsI:Tl crystal was coupled to a Burle 8850 photomultiplier tube (PMT) and excited with 148 Gd ( E α =3.18 MeV) and 137 Cs ( E γ =0.662 MeV). The timing pulses (50 Ω terminated dynode signal) from the PMT base were directly input to a GaGe CompuScope 8012A/PCI TM (12-bit, 50 MHz dual channel digital oscilloscope card) that resided in a P6-300 MHz personal computer. Individual digitized pulses were processed via a LabVIEW TM V 4.1 interface to the oscilloscope. The ratio of the charge collected over a short time interval to the total charge collected was used for the single parameter pulse shape spectrum while the total charge collected was used for the single parameter pulse height spectrum. The dual parameter spectrum was produced by displaying the pulse shape and pulse height information for individual pulses on a 2-D grid. The digital oscilloscope with LabVIEW TM interface offers a versatile data acquisition system for pulse shape, pulse height and dual-parameter analyses.

Left ventricular pressure and volume data acquisition and analysis using LabVIEW TM

To automate analysis of left ventricular pressure-volume data, we used LabVIEW TM to create applications that digitize and display data recorded from conductance and manometric catheters. Applications separate data into cardiac cycles, calculate parallel conductance, and calculate indices of left ventricular function, including end-systolic elastance, preload-recruitable stroke work, stroke volume, ejection fraction, stroke work, maximum and minimum derivative of ventricular pressure, heart rate, indices of relaxation, peak filling rate, and ventricular chamber stiffness. Pressure-volume loops can be graphically displayed. These analyses are exported to a text file. These applications have simplified and automated the process of evaluating ventricular function.