Here is the list of Most Frequently Asked Instrumentation Questions and Answers for an Instrument Engineer during the technical interview round.
To increase the sensitivity of conductivity measurement, the sample is first passed through a column of cation exchange resin in the hydrogen form, which converts all cations in sample into hydrogen ions.
As a result of salts like NaCl and magnesium sulphate (which may enter into condenser through leakage) get converted into hydrochloric acid and sulphuric acid which have much higher conductivity than the salts.
In such treatment, CO2 is unaffected. but amononia, / hydrazinc and caustic soda are completely removed from sample..
This type of measurement known is cation conductivity measurement. (and is proportional to the mineral carryover and independent of CO2 hydroxides,carbonates,NH3 or amines concentration) and the conductivity measurement made directly without passing the sample through the cation exchange resin is known as specific conductivity measurement
Contacts having not potential. E.g. Relay contacts/ field switches contacts. They are used in logic circuits. A potential free contact is usually wired into an electrical circuit. However it must be ensured that the contact ratings are suitable for the service in which it is used.
There are two different types of torque measurements:
1) actual instantaneous torque
2) dynamic torque where primary objective is to measure variations of torque rather than the torque itself e.g. torque measurement in case of centrifuge.
Torque can be measured by
1) using an appropriately connected strain gauge transducer,
2) measuring the twist (angular) of an elastic element e.g.. The power transmitting shaft of a rotating machine or the twisting of torque tube in a displacer type level transmitter.
In case of power transmitting rotating shafts, two identical slotted discs are installed at opposite ends of the shaft. Optical pickups are used to generate electrical pulses. Speed of the shaft is also measured.
The phase difference between two pulse trains is related to the twist in the shaft, which in turn is related to the torque transmitted.
Cooling fans are used to prevent transfer of heat of the process medium to the electrical parts of the switch and maintain their temperature within suitable limits.
Smart tuning, also known as self-tuning, refers to the ability of a controller to adjust its parameters/response automatically for optimum control loop performance when process parameters/response/characteristics change.
Typically this is performed by a combination of mathematical calculations and heuristics (intelligent decisions based on the designer’s experience) and continual measurement of process characteristics.
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nice
Explanations is superb
Q 11 Answer
zero suppression means the transmitter range is above then zerolike 100 or 250 etc. its called zero suppression
if the range below then zero its called zero elevation like -250 or-100 etc
Q 12 Answer
we use the "O" ring in between transmitter body to kidney flange or manifold for removing the process leakage