Pulse timer

Two AC inputs are connected, the Remote Chart ON/OFF actually determines whether high or low chart speed will be used (high speed when key switch is on). The Pulse Timer input is not used at present. 

FIG. 17-60 Reverse-pulse fahric filter (a) filter cylinders (h) wire retainers (c) collars (d) tube sheet (e) venturi nozzle (f) nozzle or orifice (g) solenoid valve (h) timer (/) air manifold (k) collector housing (/) inlet (m) hopper (n) airlock (o) iipperplenum, (Mikropul Division, US. Filter Coip.)... 

The detector signal is conditioned through a single channel pulse height analyzer whose output pulses are fed to a scaler-timer in the single crystal controller. 

This output is fed to a scaler which counts the number of pulses it receives. A timer gates the scaler so that the scaler counts the pulses for a predetermined length of time. Knowing the number of counts per a given time interval allows calculation of the count rate (number of counts per unit time). 

However the probe, like the bath, does suffer from the same difficulty with respect to temperature control. This problem has been alleviated to some extent in modern instruments by the incorporation of a pulse mode of operation. Quite simply this consists of a timer attached to the amplifier which switches the power to the probe on and off repeatedly. The off time allows the system to cool between the pulses of sonication. The on time is represented as a fraction of the total time involved in the cycle (about 1 s) i. e. 100 % is continuous sonication while 50 % represents 0.5 s bursts of power every 0.5 s. 

A simpler variation would be to use a normal Hall ignition system where you use the induction pulse to trigger a timing circuit to open the HV combined circuit for a specific period of time. The timing can be simple capacitor based or use a simple 555 1C timer with an adjustable variable resistor used to set the actual timing of the firing period. 

With a few components, the 555 timer can be configured to detect missing pulses in a data stream. The schematic for this type of configuration is shown in Fig. 6.7. 

This circuit is actually a clever use of the timer characteristic of the 555 as long as the pulse spacing is less than the timing interval generated by R2 and Cl. Therefore, this circuit not only detects missing pulses, but variations in duty cycle, variations in frequency, and even a terminated pulse stream. Figure 6.8 shows the breadboard in detection... 

Disadvantages Not a true missing pulse detection circuit, actually a timer circuit File names 555 mpd (IsSpice), 555 mpd2 (PSpice), 555.mpd3 (Micro-Cap)... 

LT, low-temperature housing A, amplifier S, pulse shaper D, discriminator CT, counter T, timer, (b) Principle of the discriminator Vj and V2 are the low and high signal limits... 

Figure 1. Block diagram of single-photon time-correlation apparatus from Barker and Weston 11 HV, high-voltage supplies L, lamp PI, photomultiplier M, monochromator FURN, furnace C, sample cell LP, light pipe F, interference filter P2, photomultiplier AMP, amplifier DISCI, discriminator D1SC2, discriminator T-S, timer scaler DL, delay line TAC, time-to-amplitude converter BA, biased amplifier MCPHA, multichannel pulse-height analyzer TTY, teletype printer and paper-tape punch REC, strip-chart recorder.

Feed gas is supplied in pulses of up to about a second in length from a compressor and a surge tank. The pulse is controlled by a solenoid valve and a timer. During this feed pulse the exhaust solenoid valve is closed. Following the feed pulse both valves at the feed end are closed for about 0.5 to three seconds this period is called the delay. Finally the solenoid valve on the exhaust or purge line opens for a period of about five to 20 seconds. Since the pressure in this line is maintained below that in the feed line, a reverse flow of gas from the bed occurs. 

In the time-correlated single-photon counting (TCSPC) technique, the sample is excited with a pulsed light source. The light source, optics, and detector are adjusted so that, for a given sample, no more than one photon is detected. When the source is pulsed, a timer is started. When a photon reaches the detector, the time is measured. Over the course of the... 

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