Pulse generators sensitivity

Photoacoustic or optoacoustic spectroscopy, which detects the absorption of a pulsed laser in a cell by the pressure pulses generated when the light energy is degraded to heat, which is claimed to have sensitivities of 0.4 ppb for nitric oxide and 5 ppb for ethylene, and which can measure the absorption spectra of solids and dusts. ... 

The UW detector uses Sharp low beta anticoincidence electronics and scalers (low beta I) with voltage sensitive preamplifiers (Sharp is a division of Beckman Instrument Co.). The electronic window selected by a pulse generator is 0.75-100 mv. input for the anticoincidence channel and 0.5-oo mv. for the guard channel. The discriminators were set up for use only in natural radiocarbon measurements. 

Ala-Kleme and collaborators have probed the ability of six heptadentate, one octadentate, and three nonadentate polyaminocarboxylates to sensitize Ybm emission by an electrochemically generated process (fig. 62). In these experiments, peroxidisulfate is added to the chelate solutions and electric pulses generate hydrated electrons (E° = -2.9 V vs SHE) which trigger the following reactions ... 

The rise time T, of the pulse generated by a semiconductor detector can be measured at the output of a charge-sensitive preamplifier. If the preamplifier is sufficiency fast, T, is determined by the following factors ... 

A microcomputer acts as a pulse generator and sensor signal processor to pulse the sensor heater at a duty ratio of 8/1000 for an effective power consumption of 14 mW. This particular sensor is sensitive to carbon monoxide and hydrogen gas. 

A programmable pulse generator produces the pulse sequences that drive the p-i-n diode switches in the microwave circuit. To resolve the microwave-induced changes in the phosphorescence intensity from the steady-state emission (usually a few percent or less) phase sensitive detection of the photomultiplier output at the microwave sequence repetition frequency (Fh is typically 150-350 Hz) is applied using a lock-in amplifier. 

Practical ratemeters deviate from the ideal device performance in several respects. These include a deadtime caused by the charge pulse generator, nonlinearity in the plot of analog output voltage versus input rate, errors in the meter reading, and sensitivity of the output signal to temperature variations. All of these deviations are controllable to some extent by the choice of design. 

Fig. 5 Simultaneous excitation of HTC and Eu(III)-l-NCS at oxide-coated aluminum electrode [68], Conditions Oxide-covered Al-strip working electrode, Pt-wire counter electrode, coulostatic pulse generator, appUed pulse voltage -40 V, pulse frequency 20 Hz, pulse chaige 120 pC 0 2 M boric acid buffer at pH 9.2, 1x10 M KzSzOg. Time-resolved spectra were measured with an instrument having relatively good sensitivity but poor resolution [79]...

In conventional HSQC experiments, the preparatory recycle period is determined as a function of the Tj( H) values, typically 1—2 s in routine analysis. Thus, a simple solution to speed up data acquisition should be the reduction of the recycle delay between scans to some milhseconds. However, fast pulsing generates partial signal saturation and the overall sensitivity can be significantly decreased. 

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