Matrimony.com Limited interview questions and answers - Wikitechy

Why we don’t use 2-20mA, 1-20mA, 3-20mA or 10-50mA signal instead of 4-20mA ?

Editor — Thu, 05 Aug 2021 07:07:00 +0000

Why we don’t use 2-20mA, 1-20mA, 3-20mA or 10-50mA signal instead of 4-20mA ?

Generally, in a transistor some amount of voltage is required for turning it on.
This voltage is the cut in voltage. Up to this voltage it exists a nonlinearity in its characteristics. Beyond this cut in voltage the characteristics of transistor is linear.
This nonlinear region lays between 0-4mA, beyond 4ma it linear. That’s why 4-20 mA range is used.

Due to some following reasons 4-20mA signal is used,

4-20mA has an inherent ‘live zero’. Zero engineering unit is 4mA not 0.0mA indicates an open circuit, fault in the line which is not valid.
4-20 mA has little, if any, signal loss in its circuit; current regulation compensates for minor resistances in terminal boxes, whereas voltage drop across resistances for voltage signals creates an error.
S 4-20 mA signal is less susceptible to noise pickup than a voltage circuit. So it is free from interference from other signals.
4-20 mA works at a relatively long distance(>1 Km ) boosting the power supply voltage will drive the signal further.

Editor — Thu, 05 Aug 2021 07:05:18 +0000

How to calculate the flow rate in Vortex flow meter ? What is K factor ? Can you give me an example calculation to understand the same as better ?

Vortex flow meters are flow sensors that detect the frequency of vortices shed by a bluff body placed in a flow stream.
The frequency of the vortices is proportional to the flow velocity.

Where:

f_v is the frequency of vortex shedding.
D is the diameter of the pipe.
w is the width of bluff body over diameter of pipe.
K is the a constant for all fluids given design of meter. A k factor is introduced to compensate for the non-uniform profile of pipe flow.
S is the Strouhal number, determined experimentally.

K-factor is a dividing factor.
The term is usually encountered when dealing with pulse signals although analog K-factors are sometimes used.

Editor — Wed, 04 Aug 2021 06:37:39 +0000

Bacterial toxins present in food causes food poisoning.
This leads into nausea, vomiting, abdominal discomfort diarrhea and even death.
The food poisoning bacteria are Clostridium botulinum, Salmonella enteritis, Staphylococcus aureus etc.

Souring of milk, rotting of vegetables and meat are caused by many saprotrophic bacteria.

Spirochaete cytophaga cause cellulose degradation thereby destroying textiles, wooden articles and canvas.

Denitrifying bacteria like Thiobacillus denitrificans, Micrococcus denitrificans, Pseudomonas aeroginosa convert soil nitrates and ammonia into free nitrogen and thus reduce the soil fertility.

The improved variety of infective agents (bioweapons) are widely been used as an agent of effective weapon of bioterrorism.
The antibiotic resistant microorganisms like Bacillusanthracis are being produced at large scale and when these are released at strategic locations, they cause acute infection of anthrax.
The spores of B. anthracis can be produced and stored in a dry from keeping them vaible for decades in storage or after release.
An attack with bioweapons (antibiotic resistant strains mould) leads to spread of communicable diseases like anthrax and plague etc.

Editor — Wed, 04 Aug 2021 06:37:36 +0000

Mammals give birth to their young ones. The babies are fed by its mother’s milk which is fed through her breasts.
Some mammals have two breasts while some have eight or even more the mothers show intensive care towards the babies.They give them love and affection.

They eat their own babies if faced to a threat. The mothers give them warmth by lying down beside them or making pillows from dried grass and even feathers to keep the babies away from the predators they may keep the babies in a hole underground or something.
During these times the mothers are very protective that they may not even allow any other creature to pass nearby that area.