The basic reason is that the power supply is -24 VDC. So since the supply voltage is negative the output voltage will be as well.

IRD at one time made prox probes with a positive supply and as a result a positive output.

Way back in the 50's uncle Don Bently made a design decision to use a negative supply voltage (back then it was -18 VDC rather than -24 VDc in the modern device) in his circuit. This decision has stuck and is now even included in the API standards.

Thank you very much for your help.

I know that supply is negative, what I acually want to know is whether it is the only choice to use negative supply and output as well. Wasn't it possible with Positive supply? Is there any other reason for using negative voltage except for the API standard.

Has there been any proximitor with positive power supply?

thanks,

because the proximeter is use a nigative power supply since it is made or design by bentlley. hence, the output will be negative.

So, Do you know the reason for using negative voltage instead of positive?

This Thread has sparked my interest as well, Can someone explain the benifits and/or reasons for using the negative voltage instead of the positive voltage?

As I said, a positive voltage can and has been used. Bently made a design choice to go with a negative voltage, and that is the way it has been.

Some things are just a matter of convention.

Positive are also there for example.

Metrix 5465F is -ve gap voltage

Metrix 5465E is +ve gap volatge

It does not make much of a difference wether you use positive or negetive voltages. It is -ve because Bently started with the design of -ve and now we stick to -ve.