A temperature switch is an instrument that automatically senses a change in temperature and opens or closes an electrical switching element when a predetermined temperature level is reached. Figure 6.47 is an illustration of a common type of temperature switch which has an accuracy of ±1 F maximum.
This temperature switch is provided with an adjustment screw at the top end in order to change the actuation point. In order to facilitate its mounting on the hydraulic system whose temperature is to be measured, the bottom end of the switch is provided with threads. As in the case of pressure switches, temperature switches can also be wired either normally open or normally closed.
Leaky fittings are a cause for concern in hydraulic circuits especially with increase in the number of connections. This is where manifolds play a very important role. Their incorporation in a hydraulic circuit helps drastically reduce the number of external connections required. Figure 6.50 shows a simple manifold commonly employed in hydraulic systems.
In the case of modular valve stacking, the manifolds used are provided with common pressure and return ports, with each valve station being incorporated with individual A and B work ports. Manifolds are normally specified according to system pressure, total flow, number of work stations and valve size and pattern.
Flowmeters are used to measure flow in a hydraulic circuit. As shown in Figure 6.49, flowmeters mainly comprise of a metering cone and a magnetic piston along with a spring, for holding the magnetic piston in the no-flow position.
Flow meters are normally not bi-directional in nature. They in fact act as check valves and block flow in the reverse direction. Initially the fluid entering the device flows around the metering cone, exerting pressure on the magnetic piston and spring. With increase in flow in the system, the magnetic piston begins compressing the spring and thereby indicates the flow rate on a graduated scale.