Answer / mugil

Instrument Earth:
Instrument Earth is also called as Reference earth.Instrument Earth all individual shields(Screen) and
over all shields single or multi pair cable shall be isolated from electrical earthing due to avoiding interference and terminated different bus bar.
Instrument bus bar will be connected to grounding dispatcher by 25 sqmm green- yellow cable.Grounding dispatcher to earth pit is connected to 70 sqmm green -yellow cable.

Electrical Earth:
Electrical earthing also called as dirty earth or protective earth.It is used to protect the power system,electrical equipment and personnel from electric shock.

Answer / jigaranadkat

Dear Shashank,

There are mainly three types of earthing used in instrumentation.
1) Power earth
2) Signal / Instrument Earth
3) IS Earth

Power earth :
Provides ground reference to all power cables. Usual practice to have MAX . Earthing resistance ~ 100 Ohms (There is no harm if it is lower)

Signal / Instrument Earth :
Provides ground reference to all Signal cables (including ICS systems).
Usual practice to have MAX . Earthing resistance ~ 10 Ohms (There is no harm if it is lower)

3) IS Earth (Intrinsically Safe Earth) :
Provide ground reference for all IS signals. MUST NOT EXCEED 1 OHM.

You can have multiple earthing pits of same kind of earth and can be connected in parallel in order to reduce the over all resistance.

Answer / elam

How long distance need to plant earth to instrument earth

what do we mean by hook up drawing. what r the information we get from it?

7 Answers   Reliance,

---

sir, i preparing hpcl,ongc,barc,hal exams(instrumentation engg)pls send a placement papers

2 Answers   BARC,

---

what is output of FOUNDATION FIELD BUS transmitter

0 Answers  

---

What is the use of double seated valve?

0 Answers  

---

State four different types of flow measurement.

4 Answers   ADMA OPCO,

---

i have a dp tx range is 5000mmwc. in which calibration i use in a open tank.1.5*3.5*2.5 mtr.for level msmnt. what is the calculation.

2 Answers   Bajaj Hindusthan,

---

What is the differerence between hysterisis and linearity.

0 Answers   CCIE,

---

How do you troubleshoot accelerometers used in Vibration monitoring/tripping

1 Answers   Air Liquide,

---

what is the use of shield cable?

2 Answers  

---

During valve sizing from all calculation you got flow coefficient CV 12,than what it means? like for selecting pressure transmitter if your MAWP is 12 bar than you select a capsule of max. 20 bar which cover your mawp 12 in same way for selecting control valve If CV is 12 than how we use it in selecting valve??????

1 Answers  

---

Explain why plc require in analog input 4-20amp & 0-10 volt?

0 Answers  

---

A DP Endress and Hauser flow transmitter is always tripping pump at low flow. set point is 74 cubic meter/hr. Thorough impulse line flushing and zero calibration has been done, yet problem persists. What do you think is the problem and how do you rectify this fault?

5 Answers  

---