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History of 3-15 psi, 10-15 mA, and 4-20 mA signals

S Bharadwaj Reddy
Before 4-20 mA the signals were 3-15 psi and 10-50 mA. These signals all have a “live zero” (3 psi, 10 mA, and 4 mA) rather than a “dead zero”...

Vibrating Tube Densitometers Working Principle

S Bharadwaj Reddy
One of the many parameters that must be accurately measured for product quality control, custody transfer, process control, or liquid interface detection purposes is liquid density. Often density measurement is...

Troubleshooting a 4-20mA Current loop

S Bharadwaj Reddy
The basic layout of every 4-20mA loop consists of a power supply, a transmitter, and passive loop devices. The supply produces the energy to run the loop. The transmitter controls...

Why 4-20 mA Standard is so popular ?

S Bharadwaj Reddy
4-20 mA Standard 4-20mA has an inherent ‘live zero’. Zero engineering units is 4.0mA, not 0.0mA. 0.0mA indicates an open circuit, a failure or a fault mode like cut wires...

Fire and Gas System Loop Checks Procedure

S Bharadwaj Reddy
Guidelines to be followed by Panel Engineer during Fire and Gas System Loop Checks: 1. Location of the FGS Tag no. to be checked (As per Drawing, it should be...

How to Do Loop Checks During Plant Pre-Commissioning

S Bharadwaj Reddy
Basic Guide lines to be followed during DCS Loop Checks (Follow P&ID and Instrument Index): 1. Location of the instrument Tag no. to be checked (As per P&ID) 2. Tag...

How to Do Logic Checks During Plant Pre-Commissioning

S Bharadwaj Reddy
Basic Guidelines to be followed during Logic Checks (Follow Cause & Effect, Control Narrative, P&ID and Latest Alarm & Trip Schedule): 1. Understand the Cause & Effect Matrix, if any...

Why Use a Current Loop?

S Bharadwaj Reddy
A Little Bit of History Before the advent of electronic circuitry, process control was a wholly mechanical endeavor. Facilities used pneumatic control signals where controllers were powered by varying pressures...

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