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Why vibration siginal negative voltage ?

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تم إضافة السؤال من قبل mohamed eliwa , instrument and control engineer , egyptian maintenance company 'emc'
تاريخ النشر: 2014/04/08
khalid Abdur Rehman
من قبل khalid Abdur Rehman , instrument technician , dh fertilizers limited

yes the circuit used pnp transistor which needs negetive signal for biasing butt its actual reason is that our harmonics and noise signals which are present every time in our medium are positve so it can not affect the vibration signal. so this is the main reason that our vibration signal is negetive and we precisely and accurately measure the vibration of rotating equipment.

Hussam Adnan, CPMgr
من قبل Hussam Adnan, CPMgr , Maintenance Manager , Teeba Investment for Developed Food Processing Co.

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.

Ali Raza lakhwaira
من قبل Ali Raza lakhwaira , Instrument and Controls Foreman , Adnoc Onshore

what differ between normal power supply and loop power supply

 

mohamed eliwa
من قبل mohamed eliwa , instrument and control engineer , egyptian maintenance company 'emc'

Please  lakmuddian  send me  document simply describe how measure vibration and difference between radial and sismic and kay phasor

LAKMUDDIN AHMAD
من قبل LAKMUDDIN AHMAD , Lead Engineer, Instrument Control and Communication , Asyad International Co. Ltd.

your answer is already hidden in your question that is PNP( positive-negative-positive). In PNP there is Emitter Base Junction and Emitter is at +2v. Then how you can give a +ve voltage???

Main funda of the NPN and PNP is electrons & holes. In PNP holes are majority careers. Since the Base Collector junction is always at reverse biased then the opposite polarity voltage (-ve) shoulde be for the Collector. That is why Base of the PNP transistor must be -ve with respect to Emitter. and Collector is also more -ve as compare to Base.

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