Golgappa.net | Golgappa.org | BagIndia.net | BodyIndia.Com | CabIndia.net | CarsBikes.net | CarsBikes.org | CashIndia.net | ConsumerIndia.net | CookingIndia.net | DataIndia.net | DealIndia.net | EmailIndia.net | FirstTablet.com | FirstTourist.com | ForsaleIndia.net | IndiaBody.Com | IndiaCab.net | IndiaCash.net | IndiaModel.net | KidForum.net | OfficeIndia.net | PaysIndia.com | RestaurantIndia.net | RestaurantsIndia.net | SaleForum.net | SellForum.net | SoldIndia.com | StarIndia.net | TomatoCab.com | TomatoCabs.com | TownIndia.com
Interested to Buy Any Domain ? << Click Here >> for more details...

why we use -ve voltages in vibration prob?

Answer Posted / steve sabin

As a 20-year Bently Nevada employee, and as someone
responsible for answering such questions over the years
within our company as well as externally, allow me to
explain the rather interesting circumstances behind the use
of negative voltages (-24 vdc) for powering eddy current
vibration oscillator/demodulator devices.

The short answer is that when Don Bently worked on making
solid-state versions of the eddy-current measurement system
(it was actually originally designed in the 1930s by GE
engineers using vacuum tubes), he had a choice between
using N-P-N transistors or P-N-P transistors. At the time,
transistors were quite expensive, so he chose the least
expensive of the two: P-N-P (apparently, PNP transistors
they were less expensive to manufacture 50 years ago than
their NPN counterparts).

Because the circuits used PNP transistors, a negative bias
voltage was required rather than a positive bias voltage.
Don chose -18V. This was later changed to -24V to allow
more linear range from the transducer.

At that time, the industrial instrumentation community had
not yet standardized on +24 vdc, and by the time they did,
there were so many Bently Nevada eddy current vibration
sensors installed that changing to +24V rather than -24V
was not greeting with enthusiasm by users. Hence, it has
remained -24V to this day.

This was not a deliberate effort to "be different" or "non-
conformist" on the part of Bently Nevada. It was quite
literally based on which components were the least
expensive when the technology was originally introduced 50-
plus years ago.

Regards,

Steve Sabin
Marketing Communications Manager
Bently Nevada Asset Condition Monitoring
GE Energy Services

Is This Answer Correct ?    24 Yes 0 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

please tell me what is a light up procedure of Cfbc boiler and what it's axuillaries of cfbc boiler?

8672


why use 50% lel methane gas concentration for gas detector calibration instead of 60% lel gas concentration whereas the hi alarm set at 60% lel.

2738


Is it ok, to use non-contact type Radar type LT, on a tank that is half circular from the bottom side? If yes the, isn't the waves gonna bent in other directions? 

2188


how many type of plug are used in pneumatic control valve,name them.

5453


ORP sensor working principle?

2016


where uses EXe /EXd/Exo/Exn/Exp/Exq/EXia

9927


How to erection of DCS Panel at site step by step

1503


(1) In turbine, what does term CDP, NI, NH, HSSOC, means. (2) What is the purpose of LO overhead tank in turbines.(3) An equipment is certified for EEX, IA, IIC,T6, what do you under stand by this.(4) what is SURGE, and how it is prevented, what is the purpose of bypass valve across AS valve.(5) Give 2 application of quartz crystal used for process parameter measurement.(6) what is meant by cold float of compressor shaft. (7) state four different types of flow measurement. For gas flow measurement mmscfd is the common unit. Expand the unit and specify significance of word S in the unit.(8) what is meant by Gap voltage, in vibration measurement. Normally how much Gap voltage is set and state the reason.(9) what will the new flow factor if D/P transmitter is Re-Ranged from 25” wc to 50” wc.(10) what is the usage of QDV & Volume booster.

4046


how to calibrate steam control valve in steam turbine

3332


what is surge and how is it prevented, what is the purpose of bypass valve across AS valve.

1980


How we can check the 2 wire proxy switch? & how it is connected to DI MODULE OF PLC?

2606


how to connect transmitter measuring sulfur process? 1-by using long impulse line or 2- by using coated short impulse line

2115


Calibration of controller (pneumatic)

1982


What is the Working principle of Dozing valve?

2217


Why all the drains(Gland sealing,ESV,Casing inlet etc) are directly connected to the flash tank instead of hotwell of the condensor in the power plant? My Email Id:naba02222@gmail.com

2291