Vibration & Thrust Monitoring

Probably so that you will likely have to use a separate power supply for this sensor. Why did you select Proximeter to measure your parameters of Vibration and Thrust if this is a problem?

Admittedly, it is unusual to have a DC-powered industrial device powered by a negative voltage with respect to ground, and I've wondered the same thing while examining Bently-Nevada proximitor units. Redfred's answer makes sense: if everything else runs on a +24 V supply, this is one way to ensure you connect it to the proper supply (the -24 VDC supply on the Bently-Nevada rack).

Undefined: "we".

Ask Bently Nevada [now buried in GE]

I wonder if it is because proximitor was developed in days when germanium (PNP) transistors were the only available choice and supply was usually negative to common.

When silicon came along, they just went to PNP silicon - else they would have had to change the construction or power supply polarity, giving either a performance problem or spares compatibility problem for existing systems.

With critical sensors it is often unwise to let the customer power them from whatever "24V" supply he has. Ripple and noise from the supply could easily look like vibration! This results in a defect investigation (followed by modification to correct problem) which costs far more than an integral power supply.

Hi,

I had the opportunity to go to Bently Nevada training offered by GE (they own Bently Nevada) when the instructor talked about negative voltage. Some people asked why negative voltage is used, he said that Mr.Bently decided to use negative voltage for no specific reason.

All the Bently Nevada Racks we have are powered with 110 volts AC.

The racks have -24VDC integrated redundant Bently Nevada power supply modules these modules supply power to temperature,thrust, vibration..... modules(cards) via back plane.

There is no "stand alone" or external DC power supplies used to power the modules; Bently Nevada DC power supplies have to be used.

I am not sure where the confusion of supplying negative or positive DC power comes into play,the only power being supply to the rack is 110 volts AC.

Thank you