Position Switching

Limit Switches and Stem-Position Transmitters Travel-limit switches, position switches, and valve-position transmitters are devices that, when mounted on the valve, actuator, damper, louver, or other throtthng element, detect the component s relative position. The switches are used to operate alarms, signal hghts, relays, solenoid valves, or discrete inputs into the control system. The valve-position transmitter generates a 4-20-mA output that is proportional to the position of the valve. 

The manual-automatic transfer switch is a five position switch that alters the mode of operation. 

Online SPE after conditioning of the SPE cartridge, the sample solution is flushed into the cartridge by the washing solvent after a positional switch of the injection valve. A large volume of washing solvent is used to clean up the sample. 

The U.S. Army Defense Ammunition Center and School is employing the use of intrinsically safe electrical circuits in equipment designed to demilitarize and renovate munitions - from small arms to large projectiles. This is accomplished by using pneumatics and hydraulics to provide the power, while using position switches and solenoid valves linked to programmable controllers to direct the total machine process. 

FIGURE 4.5 Example of coupling of two 6-port two-position switching valves. (Reprinted with permission from Tanaka, N. et al., Anal. Chem., 76, 1273, 2004. Copyright 2004, American Chemical Society.)... 

Scheme 25 Photochemical switching processes of LC-phase 41 and chiral dopants M-c/s-17a and P-trans-17b, representing a three position switch.

Fig. 2.15. Schematic automated isocratic and gradient elution nemo-liquid chromatograph/ capillary electrochromatograph according Alexander et al. (reproduced from Ref. [44] with permission of the publisher). 1, high-voltage power supply (negative polarity) 2, platinum electrode 3, outlet reservoir vial 4, UV detector with on-column flow cell 5, nanocolumn 6, two-position switching valve 7, jack stand 8, fused-silica make-up adapter (split device) 9, ground cable 10, internal loop micro-injection valve 11, plexiglas compartment 12, autosampler 13, dynamic mixer 14, micro-LC pumps.

The amplifier used with the reference signal may be used in either a unity or variable gain configuration, controlled by a two position switch to the front panel. The amplification is variable from a gain of 0.5 to approximately 2.0. The variable amplification is used to balance the sample and reference signals. 

Umehara T, Kawai H, Fujiwara K, Suzuki T (2008) Entropy- and hydrolytic-driven positional switching of macrocycle between imine- and hydrogen-bonding stations in rotaxane-based molecular shuttles. J Am Chem Soc 130 13981-13988... 

All of the bases commonly fonnd in DNA [adenine (A), cytosine (C), gnanine (G), and thymine (T)] can undergo spontaneous, pH-dependent chemical changes called tautomeric shifts (2). The base T normally exists in the keto form (C=0) in the C-4 position, bnt it can occasionally exist in the rare enol form (C-OH) (Fig. 1). Under snch circnmstances it can anomalously pair with G in the nsnal keto state. Conversely, the C-6 position of G in the rare enol form can pair with T in the usual keto form (Fig. 1). The same is true of the N-6 position of A, usually in the amino form (NH2), switching to the imino form (NH) tautomer in which case, it can mispair with cytosine in the amino form (Fig. 1). Reciprocally C can mispair with A when the C-4 position switches to the rare imino form (Fig. 1). 

Fig. 2-10. Wheotstone-bridge circuit for thermistors. Ri, 1,0000 wire wound Rj, 1,OOCO wire wound Ri, 2,0000 10-turn Helipot R4, 2,OOCO R3, 5,0000 Re, 10,0000 Di, thermistor having 500—2,0000 resistance at operating tenpsrsture Si, single-pole four-position switch (sensitivity control) M, 0—25/sa met, or hotter, e galvanometer, with about a 2,0000 interne resistance.

Fig. 4-6. Detector circuits for vapor-phase chromatography, (a) Thermistor detector Di, D=, Victory Eng. Corp. 32A12 thermistors Ri, Ri, 1,0000 wire wound resistors Rz, 1,0000 Helipot Rt, 10,0000 1% carbon film resistor Rs, 5,0000 1 % carbon film resistor Rt, Rj, 2,5000 1 % carbon film resistor Sw, single-pole four-position switch, (b) Hot-wire detector Rz, filament current control, to adjust filament current between 150—300 ma ( 20 ohm 5w) Ri, R4, reference detectors Rs, R, sample detectors Re, zero control 20 Re, 600 1 % carbon film resistor R, 300 1 /, carbon film resistor R, 150 1% carbon film resistor Rse, 7.5Q 1 % carbon film resistor Rs, 7.SCI 1 % carbon film resistor M, 300 ma meter,- S, single-pole six-position sv/itch.

There are two dials on the front panel of the unit. One is marked E, for energr, or LLD, for lower-level dial the other is marked AE or ULD/AE, for upper-level dial/AE. There is also a two-position switch with INT (integral) and DIFF (differential) positions. In the INT position, only the E dial operates, and the unit functions as a discriminator. In the DIFF position, both E and AE operate, and the unit is then a single-channel analyzer. 

Sensors - For ESDI, the sensor is a pressure switch. For ESD2, two pressure transmitters and two position switches mounted on the separator inlet valve are sensors. The pressure transmitters and limit switches are configured for loo2 voting. The position switches are included as part of this safety function since there is a direct correlation between the closing of the separator inlet valve and high line pressure. 

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