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.

What are the types of control valves available

0 Answers   CCIE,

---

1.what is beta in control valves? 2.what is the condition followed by light in LASERs? 3.1kg/cm2=?psi 4.Integral action reduces what? 5.about vena contracta 6.a simple RC circuit 7.thermistor material's temp coefficient of resistance 8.if wave passes through the thicker area of a chord to a thinner area what changes will occur to wavelength? 9.if 4-20 mA represents 0-10 kg/cm2 what will be the current when pressure is 5 kg/cm2.................

0 Answers   Lurgi,

---

what is the role of proportional in process control?

6 Answers   OGDCL, Trident,

---

Why 1-5 vdc a standard?

1 Answers   Process Control Technologies,

---

why vortex flow meters and electro magnet flow meters are used in water treatment plants

1 Answers   Elite Construction,

---

---

If a transmitter is installed 10 m below its tapping point how much pressure exerted if fluid is water?

10 Answers   QAFCO,

---

How does one detrmine the direction of movement of core in an LVDT?

2 Answers   Honeywell,

---

why we are using orfice plate? then difference between orfice 7 nozzle plate?

1 Answers   Flour Tech Engineers (P) Ltd,

---

how to calculate interface capelary level transmetar lower S.G.0.54 and uper S.G. 0.26 and h=490 mm

3 Answers  

---

how flame detectors sense the flame.

3 Answers  

---

how to calibrate load cell

0 Answers   Siemens,

---

what are different types of cables used in instrumention how to calibrate a level transmitter online ( rosemount )

1 Answers  

---