Answer / naveed iqbal

actually in proximaty probes inside used PNP tanasistor.so
transistor baising supply need - dc voltage.

Answer / chandrakant sahu

There is PNP type transistor used in ocsilator and also ti keep minimum interference negative voltage is suitable for this

Answer / waleedmahmoud

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

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.

Answer / md. rizwan

Because we measure the negative voltage in vibration system.

Instrumentation symbols interpration, P& ID, Logic diagram analysis, Electrical drawing analysis.

0 Answers   CCIE,

---

How can I make calculation for Install level transmitter (DP) for open tank and cloes tank?

1 Answers   Petrofac,

---

how to caluculate flow by using transmitter?tell me plz I am eagerly waiting for your reply..

2 Answers   Agi Glaspac, Reliance Power,

---

What are the type of bonnets in the control valves?

0 Answers   CCIE,

---

why does a transmitter o/o signal starts from 3-15psi or 4- 20mA?

11 Answers  

---

---

Why do we use triad cable for RTD to Temp.transmitter connection? Why we don't use 3 core cable?

1 Answers   Process Control Technologies,

---

Ega interview going on for power plant. Which type of question will asked. For questions

0 Answers   EGA,

---

how u measure flow?orifice measurement?why all ft in square root?

1 Answers  

---

what is the calibration standard for pressure and differential pressure transmitters?

1 Answers   Thermax,

---

what is the difference between cold loop and hot loop

2 Answers  

---

why direct mounted pressure transmitters is always installed with DBB ( double bleed block) valve in process line or top of the tanks ?

0 Answers  

---

Regarding MOS (maintenance override switch), I want to know its function and its state ( 1 or 0 when not activated ). An example will be very helpful..thank you.

1 Answers  

---