12mA while we should have 4

userxyz

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May 2002
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Hi,

Today we did a retrofit connection from Siemens S5 connectors with retrofit-adapters connected to the S7-400 front connectors. All digital IO worked okay. But the analogue signals are measuring 50% and when we measure we do get 12mA. Could this be a mass problem... ? Weird that we measure 12mA while we should have 4. All measurements are around 12mA.
Weird problem, but I think the problem is electrical... just don't know what could be wrong..

Kind regards,
G
 
No specific S5 experience, but:


My guess is that the scaling is off. 4mA is 0 for unipolar, but 12mA is 0 for Bipolar.
 
Maybe I did not understand it well but:

12mA is just the average value between 4 and 20mA and is the expected reading for an analog input at 50%.

Where is the problem ?
 
Measure

Hi,

The problem is that everything is measuring at 12mA. Flowmeters that do not have actual flow, volume measurement while there is nothing in the tank... etc...
I am think in a direction of a Mass problem...

Kind regards
C

Maybe I did not understand it well but:

12mA is just the average value between 4 and 20mA and is the expected reading for an analog input at 50%.

Where is the problem ?
 
A common mistake is to use the 2-wire measurement setting instead of the 4-wire measurement setting.

2-wire: means the sensor is powered by the analog module
4-wire: means the sensor is powered by +24VDC separately.

*** you must make sure the jumper blocks on the side of the card match the setting in the hardware configuration!
 
Blocks

Blocks are correct.
C = 4DMU and in the hardware config correct also.

A common mistake is to use the 2-wire measurement setting instead of the 4-wire measurement setting.

2-wire: means the sensor is powered by the analog module
4-wire: means the sensor is powered by +24VDC separately.

*** you must make sure the jumper blocks on the side of the card match the setting in the hardware configuration!
 
Check

I checked the old S5 program.
No blocks were setted on bipolar mode.
They used type 3 on all blocks.

Untitled.png
 
Last edited:
C

Hi

I placed all jumpers in C position as we only have 4-20mA 4DMU.
But setting to C means arrow direction the texts CH0, CH1, etc.. ?

A common mistake is to use the 2-wire measurement setting instead of the 4-wire measurement setting.

2-wire: means the sensor is powered by the analog module
4-wire: means the sensor is powered by +24VDC separately.

*** you must make sure the jumper blocks on the side of the card match the setting in the hardware configuration!
 
Hmm

I'm doubting the jumper now...
Maybe a placed this one wrong... the C arrow is pointing to the text...

But maybe the arrow should be in the same direction of the info on the card... ?

If that is the case, then all my jumpers are on B, wich maybe may cause the 12mA ?


See this:
 
Hi,

The problem is that everything is measuring at 12mA. Flowmeters that do not have actual flow, volume measurement while there is nothing in the tank... etc...
I am think in a direction of a Mass problem...

Kind regards
C

Well you should go to that tank and those flowmeters and see if there is 12mA there too. Maybe someone put them in test mode to generate 50% of the full scale.

From the PLC side and that connector you only see a part of the installation.
 
Last edited:
Found

Hi,

I found the issue.
It's because of the mode blocks (PCS7).
Weird that these blocks can do things like this...

Anyway, the mode was on all analogue blocks still 80000109, and it has to be 800000203 for 4 to 20mA inputs. This is because on start-up I setted all the chanlles to 4-20mA in the hardware config and I did not a regeneration of the channel blocks in PCS7, so these thinks it is still 0 to 10V. Because my L+ is connected I think these blocks do something with the hardware and therefor we measure 12mA. After regeneration all modes were corrected and we measured 7mA instead of 12mA on a temperature measurement for example.

Module mode.png

Kind regards,
C
 

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