Monthly Archives: January 2016

What is Transmitter suppression and elevation

A very common scenario for liquid level measurement is where the pressure-sensing instrument is not located at the same level as the 0% measurement point. The following photograph shows an example of this, where a Rosemount model 3051 differential pressure transmitter is being used to sense hydrostatic pressure of colored water inside a (clear) vertical plastic tube: Consider… Read More »

Stock Tips 29/1/16

Buy Bajaj Auto @2270  SL 2255 TG 1  2315 TG 2 2325 Buy Hero moto @2452 SL 2445 Tg1 2500 TG2 2520  

Ethernet Cabling

Along with hubs came another form of Ethernet cable and connector: unshielded, twisted pair (UTP) wiring and RJ-45 “flat” connectors. These cables use multiple twisted pairs of wires instead of the coaxial cable specified in Metcalfe’s original Ethernet. The purpose of using twisted-wire pairs is to reduce magnetic signal coupling. For 10 Mbps Ethernet over UTP cable (called… Read More »

Repeaters (hubs)

Bob Metcalfe’s original design for Ethernet consisted of DTE devices connected to a common coaxial cable through the use of “tee” connectors, like this: This cabling arrangement suffered several problems. First, it was inconvenient to run through an office building, since each DTE device needed to be coupled rather closely to the main “trunk.” Short cable segments (called… Read More »

Ethernet network

An engineer named Bob Metcalfe conceived the idea of Ethernet in 1973, while working for the Xerox research center in Palo Alto, California. His fundamental invention was the CSMA/CD method of channel arbitration, allowing multiple devices to share a common channel of communication while recovering gracefully from inevitable “collisions.” In Metcalfe’s vision, all of the “network intelligence” would be… Read More »

Ziegler-Nichols Tuning method

Ziegler-Nichols open-loop tuning procedure :- The first process tuned in simulation was a “generic” process, unspecific in its nature or application. Performing an open-loop test (two 10% output step-changes made in manual mode, both increasing) on this process resulted in the following behavior: From the trend, we can see that this process is self-regulating, with multiple lags… Read More »

On-Off control sytem

Once while working as an instrument technician in a large manufacturing facility, a mechanic asked me what it was that I did. I began to explain my job, which was essentially to calibrate, maintain, troubleshoot, document, and modify (as needed) all automatic control systems in the facility. The mechanic seemed puzzled as I explained the task of “tuning”… Read More »

Working Principle of Electronic positioners

Recall that the purpose of a valve positioner is to ensure the mechanical valve’s position matches the command signal at all times. Thus, a valve positioner is actually a closed-loop control system in its own right: applying as much or as little pressure to the actuator in order to achieve the commanded valve stem position at all times.… Read More »

Working Principle of Motion-balance pneumatic positioners

Motion-balance pneumatic valve positioner designs also exist, whereby the motion of the valve stem counteracts motion (not force) from another element. The following illustration shows how a simple motion-balance positioner would work: In this mechanism, an increasing signal pressure causes the beam to advance toward the nozzle, generating increased nozzle backpressure which then causes the pneumatic amplifying relay… Read More »