Connecting Current Transducer into AI 8xI 2-/4- wire BA

Hello MFMF,

it's nice to see you again.

Your wiring is absolutly correct.

I habe onlyy some questions:

• what for current do you want to mweasure (AC or DC)
• is the direction of your current the right? (please look at the installation manual
• are the dIP-switches at the right position?

regards
CaOd

CaOd

Hello MFMF,

it's nice to see you again.

Your wiring is absolutly correct.

I habe onlyy some questions:

• what for current do you want to mweasure (AC or DC)
• is the direction of your current the right? (please look at the installation manual
• are the dIP-switches at the right position?

regards
CaOd

 Hello CaOd! 

Thank you for your time again.

1. I intend to measure DC current. Just curious, any difference if I measure AC current? Reason I ask is that multi-meter shows that there is one tap to measure both AC/DC current. 

2. Hmm, for this , I would say yes. Because if it is not, I will get an incredibly odd number. 

3. I managed to review and change one of the DIP switch. (DIP-3) It does not make much difference. Thus I revert back to default setting. Other switches seems to have no much meaning. DIP-1 says about the range (0- 25A or 0 - 50A). DIP-2 is the refreshment rate which I think it has not much effect.  

Update:

I decided to place both live(+) wire and neutral(-) wire with different direction into the hole. I also switched the DIP switch to its default setting, resulting in value to be in 60 - 80 with no voltage supplied instead of a 5 digit number (E.g. 13000). The value in TIA portal finally shown some trend. (E.g. %IW0 = 220 when 24 V - 25V, %IW0 = 100 when its 12 V)

The unusual trend happened in between 0 - 4V.  When the voltage is adjusted from 4V and below, %IW0 started to increase and stop at the value 86 at 0V. (Illustrated at SS5). Not sure why such effect happened. 

At this rate, is it safe to say that TIA portal is not at fault for now?

Thank you and looking for everyone's reply. 

Hello MFMF,

at 2.

If your current is not in the rigth direction, tehn you measure nothing.
The output of your transducer is 4 mA if the current floe not in the right direction

The differences at your measuring is that you have a sensor which based on the Hall-effect.

Otherwise is that your analog module have accuracy of 0.5 % and your sensor 0.3 %.

The other thing is that current Hall-sensors have a "problem" with low currents.
Please look e.g. at Wikipedia for the functionality of a Hall-sensor.

The difference of 86 inkrements by 0 A is (at 50A measuring range)
0.155 A = 0,3 %.(calculated 86 / 27648 * 50)

I think that TIA have here no problem, it's a measurment problem.

regards
CaOd 

Hi CaOd,

Currently, I am thinking and working on it still. I will post my other updates later. 

Technically, if nothing is in the hole, it would result in 4mA right?

I tried that but I didn't get any value in the multimeter. In TIA, whenever I connect it without the multimeter, it would show approximately -700 or 700 instead of the usual -34k or 34k for %IW0. Currently, really lost on why such thing happens, especially on the multimeter part.

If this cant be solved, I really cant determine if what the PLC/ AI module reading is in direct proportion to mA. (E.g. the INT value readed from %IW0 is related to 4-20 mA). 

Hello MFMF,

you are right if you have no cable in the transducer then you should measure 4 mA.

I'm looking forward to your updates.

regards
CaOd

Hi everyone and CaOd,

I have some updates with the topic on hand. It may not come in order but here it goes.

1) What happened is that the multimeter used - Fluke 175 has either its resistor or the fuse burnt out. (Tested with continuity test with other multimeter - multimeter shows OL/0L). This is why the readings in the multimeter is undetermined or not consistent. What was done is that we used a different multimeter to test out and there is some result. Other correction action is the placement of ammeter at different points . 

2) What the PLC TAG %IW0 is displaying (INT) that is shown in the attachments is actually displaying milliAmpere (mA). My friends and I discussed and tested out and realised that it was actually mA. Some mystery that have yet to solve is 

a) How the signal really does work? Does the signal come in a form of current ? Does the Siemens AI used the difference of Current/Voltage to step up/down as part of its calculation? 

E.g. 4.04mA @ 0V load (INT = 60), 4.12 mA @ 24V load (INT = 220 )
**** when measured from (-) transducer to (-) PLC terminal.

220mA is the current of our sample load @ 24V as supported in its technical sheet.

b) Following up with Qn 1, we are wondering why INT = 60 at 0V load. (Multimeter give 4.04 mA when measured from (-) transducer to (-) PLC terminal). Ideal Current Transducer would produce 4 mA. Does this mean that ideal result would be 4 mA would result in INT = 0? 

However, since Current Transducer is sending signal AND since Current is Signal, this would explain that the difference of value is the signal sent from Transducer to PLC. Is this true? 

Looking forward for replies and discussions. :) 

Hello MFMF,

at 2)
Ithe %IW0 nshow you a 'INT value which is depended of the current.
The measurement measure the voltage drop over a internal resistor.

At 4,04 mA is the INT-value of 60 right (calculate 60 / 27648 * 16 mA)
The difference of 0.04 mA is in the "normal" precision of your sensor.
If you have different supply voltage then have you also a little bit different quiescent current.

at 3)
yes the "ideal" result of 4.0 mA is INT = 0.

At your transducer is the current at the output the "real" measurement signal.
Your sensor should (must) have a current consumption of 4.0 mA for a high precision.

regards
CaOd