Loop Powdered Inductive Sensor Voltage and Current Fluctuation

  • Thread starter I&C Engineer_Evil Genius
  • Start date
I

Thread Starter

I&C Engineer_Evil Genius

We have 2-wire loop powered (24VDC/4~20mA) inductive sensor installed on Steam Turbine Turning Gear Motor for engaging/ disengaging purpose. This sensor basically senses the movement of plate gap (mm) and transforms this gap (mm) information into mA.

The problem is when its target moves. sensor mA & biasing voltage also starts fluctuating simultaneously (Volts fluctuates from 24VDC to 6VDC & signal current fluctuates from 5mA to 19mA).

The sensor is loop powered from INFI90 Bailey DCS (Analog Input Slave Card having Termination Unit#NTAI05). Though the Slave Card Termination unit supply remains constant.

We did this checks on several new sensors but observing the same results. Wire loop from DCS till sensor is OK. DCS card also checked, verified and found ok.

Please suggest what could be the possible reason for such fluctuation?

Sensor Model# PEPPERL+FUCHS NJ2-12GM-N
 
H

Heinrich Baumann

> We have 2-wire loop powered (24VDC/4~20mA) inductive sensor installed
> on Steam Turbine Turning Gear Motor for engaging/ disengaging purpose.

>Sensor Model# PEPPERL+FUCHS NJ2-12GM-N

I think this is what this sensor is designed to do. However, I would connect it to a digital input.

Remember Namur has a lot of recommendations, not just about analog equipment. see. http://www.namur.de/

I think you misinterpreted the namur functionality as stated with this sensor with the namur NE43 recommendation for analog signals. See http://www.divize.com/techinfo/namur-ne43.html

hope this helps.
Regards,
HeiBau
 
Is this a new installation or something that used to work?

These types of NAMUR sensors usually has a supply of 8V and switch points of 1 and 3 mA. To connect it to a control system you either need a special input module or or a switch amplifier relay like this KCD2-SR-Ex1.LB:

http://www.pepperl-fuchs.com/global...mxattrib=a_192/107877&amxattrib=a_193/107398&

to connect it to an ordinary digital input.

This is IS, but comes in a lot of other flavors as well.

Geir
 
Top