Pneumatic switching

For liquid feed, a double-channel syringe pump with two 500 pi syringes, a highspeed pneumatic switching valve and PTFE tubing with an inner diameter of254 pm was used [110] 0.5 pm PTFE microfilters were set in front of the micro mixer to remove particles. The flow rate was set to 6 ml h-1. 

Logical elements (pneumatic switching elements) as links for connective instructions... 

Multiple-column systems were previously explored in the petroleum industry and some process-control situations. In the former case, typical petrochemical samples share some similarities with biochemical samples in terms of complexity while the GC column typically receives a total sample, only certain portions of it may be of interest. Thus, selected parts of a column effluent can be pneumatically switched over to a second column for an optimum analysis, while the residual uninteresting substances (heavy ends) are being rapidly removed through backflushing. In the case of process GC analysis, such backflushing is essential to the speed of analysis required from these industrial analyzers indeed, a similar situation is often found in a clinical laboratory. 

Use of single cells which are pneumatically switched between reference and eluent gas flow (about 10 Hz sampling rate) improves the signal-to-noise ratio and avoids problems due to mismatches between reference and measuring cells. 

Ultrasensitive pneumatic switch actuated by slight mouth pressure. 

The oven contains the column, the katharometer and the pneumatic switch valve so that no condensation can take place in the switch valve. Other items of the gas chromatographic equipment not shown in Figure 7.1 include the katharometer bridge unit, the flame ionisation amplifier and the respective potentiometric recorders for the two detectors (1 mV, f.s.d.)... 

Set timer (iii) (Figure 7.1) for 5 min. Open the split heater, move it forward on its travel and close it over the sample tube. Operate the push button for timer (iii). After the set time of 5 min the pilot valve, Mi, is triggered which operated the pneumatic switch valve, F, thus allowing helium carrier gas to flow around the external loop, H, through the sample tube and flushing the liberated volatile constituents on to the gas chromatographic column. The carrier gas remains routed around the external loop, H, until the re-set button is pressed. It is then diverted through the internal loop, G. 

Simple electrical or pneumatic switches that produce a state change when the limiting condition is exceeded. These can be subdivided into sub classes ... 

Keywords Flexible electronics, polydimethylsiloxane (PDMS), microfabrication, transmission line, coplanar waveguide (CPW), pneumatic switching, metamaterials, negative index, terahertz, fishnet... 

In this section, we report on the combination of PDMS-based RF electronic devices and pneumatic valves to achieve a pneumatically-switched RF coplanar waveguide. PDMS has stable high frequency dielectric constant and low loss [21], while pneumatic valve technology offers a non-electronic form of control of RF devices eliminating electromagnetic interference and parasitic effects caused by bias lines. The outcomes present opportunities for pneumatically-switched addressable RF devices and elements. These can be utilized to control RF transmission in order to potentially activate or disable RF devices such as antenna and metamaterials [28]. 

Figure 14.11a presents a photograph of the realized pneumatic switch assembled with the CPW electrode. The... 

Figure 14.13 Measured and simulated transmission data presented in (a) and (b), respectively, demonstrates the effect of placing the valve (in its inactive, open state) on top of the CPW line. A slight increase in loss is observed. Measured and simulated data presented in (c) and (d), respectively, characterizes the pneumatic switching. A minimum 20 dB difference can be observed between the valve open (full transmission) and closed (nil transmission) states.

Figure 14.14 Return loss of the pneumatically-switched coplanar waveguide device.

Figure 14.15 Characterization of repeatability of pneumatically-switched elastomer-based transmission line. Excellent overlap of multiple measurements can be observed.

C.M. Shah, S. Sriram, M. Bhaskaran, M. Nasabi, T.G. Nguyen, W.S.T. Rowe, and A. Mitchell, Elastomer-based pneumatic switch for radio frequency microdevices. Journal of Microelectromedianical Systems, Vol. 21, Issue 6, pp. 1410-1417, 2012. 

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