I have an offset current on my analog input SM331 AI 8x12 Bit

Hi ,

i try to read a 4-20 ma signal on my analog input card.

the issu is that i have always 56ma above the sensor signal ( i measur 56ma on my input even befor i connect the sensor ) , so i m always on a max reading ( minimum 4 ma + 56ma )

how can i eliminate that

Rgds

hi,

how do you measure that?

do you have a 2-wire or a 4-wire transducer?

how is it connected?

Have a look in the manual, how to connect it, chapter 6.7:

SIMATIC S7-300 S7-300 Module data

hope this helps,

regards,

mopS04

hi,

how do you measure that?

do you have a 2-wire or a 4-wire transducer?

how is it connected?

Have a look in the manual, how to connect it, chapter 6.7:

SIMATIC S7-300 S7-300 Module data

hope this helps,

regards,

 Hi,

i take the measure by a multimeter.

its a 2-wire , i do the wiring following the manual ( CH0 two terminals ) nothing on the other CHs , desactivated from software .

thanks for the reply

how is the measurement range module setting?

it has to be on D

on what pins is the transducer connected?

for channel 0 you need to connect on pin 2 and 3.

mopS04

how is the measurement range module setting?

it has to be on D

on what pins is the transducer connected?

for channel 0 you need to connect on pin 2 and 3.

 hi,

yes its on D, and yes its connected to 2 and 3

how do you measure? in row?

4mA  + 56mA = 60mA ; this is the max. supply current per channel(see technical data)

it seems there is a short circuit on the channel.

mopS04

how do you measure? in row?

4mA  + 56mA = 60mA ; this is the max. supply current per channel(see technical data)

it seems there is a short circuit on the channel.

 i measure the current between pin 2 and 3, i found 56mA (befor connecting),after connecting 60mA, i activate the sensor i measure 76mA ( like the 56mA is an offset )

AutoGen_6129952

  i measure the current between pin 2 and 3, i found 56mA (befor connecting),after connecting 60mA, i activate the sensor i measure 76mA ( like the 56mA is an offset )

sorry it is not clear to me how you are measuring.

between pin 2 and 3? How could you measure without connecting?

When you measure current you have to measure in row:

M0+ o----(A)-----[transducer]----o M0-

Have you also tried with ext. compensation? whit a bridge between COMP+ and Mana(pin10 and 11)? like on the scetch in the manual.

mopS04

 

AutoGen_6129952

  i measure the current between pin 2 and 3, i found 56mA (befor connecting),after connecting 60mA, i activate the sensor i measure 76mA ( like the 56mA is an offset )

sorry it is not clear to me how you are measuring.

between pin 2 and 3? How could you measure without connecting?

When you measure current you have to measure in row:

M0+ o----(A)-----[transducer]----o M0-

Have you also tried with ext. compensation? whit a bridge between COMP+ and Mana(pin10 and 11)? like on the scetch in the manual.

 maybe I m wrong with the measurements, but my principle issue is why I always have maximum reading  (37260) even if nothing connected to the pin  (only +24V, jump 10 and 11 and  Mana )

it normally describes an overflow, when the installation and projecting is right.

Many users have also problems in the understanding of 2-wire and 4-wire transducers.

the difference between 2-Wire and 4-wire-transducers is that the 2-wire-transducers have their power supply through the measurement-wires. Thats the reason why only 4..20mA-range can be used with it. 4-wire transducers have the powersupply seperately.

which device are you measureing from?