Resolution issue of transducer through Siemens Analogue input

uptown47

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Hi all,

I have a linear transducer connected to a Siemens analogue input card (6ES7 334-0CE01-0AA0).

When the transducer is at its lowest it reads 6252 in the PLC (via the PIW) and at it's highest it is reading 17182.

When the machine lowers slightly the transducer value jumps by quite a large amount (around 100 each time).

I wondered whether this is an issue with the transducer just not being very sensitive or whether I could help this issue by installing a 12 'bit' resolution analogue card?

Would the fact that my card is only 8 bits make a difference (please excuse if this is a stupid question).

Thanks for any light you can shed on this :)
 
What is the stroke length and required resolution..that will answer your question tbh

I would say if it has been ok all these years it is not the analog card resolution but the wiper inside the transducer is worn out. What does 100 represent.. 0.1mm? 1 metre lol

Why not look into other transducers, for example Balluff.

Cheers
 
It is a Balluff. The value only changes when the transducer has travelled a couple of mm. The length of the transducer is about 300mm.

The transducer has never been used for anything before as far as I know.

Would putting a 14bit analogue card in make any difference in theory (assuming the transducer isn't faulty) or does it not work like that?
 
17182-6252 = working range in counts for 300mm

is 36.4 counts/mm which is pretty good.

Try connecting a meter and see if the power to the balluff is stable

Also in the 4-20/0-10 loop and see if mA/V changes are jumping.

I would say one of the component parts is faulty not the resolution
 
I think you are 'bang on' with your theory on the number of bits. The analogue inputs are 8 bit, that is a maximum count of 255, so that is 255 steps from min to max. I don't know the maximum analog output value for the card, working with your min and max will flatter the results. With max and min at 17182-6252 range is 10930, but there are a maximum of 255 steps so that is a analog value change of 43 for each step. So a jump of 100 for a small movement is not unexpected.
 
For 0-10v analogue inputs, PIW value=32767 @ 11.852 volts
With 8 bit resolution, PIW value will change in 32767/256=128 bit increments.

ana.JPG
 
This is where I get confused by the analogue inputs. It is 8 bit, so we know that it can have 255 steps. But is that 255 steps from 0% to 100% or does it include the over-range shown here as going up to 118.515. From the values given by uptown47 a single step in the 0% to 100%, or 0 to 27648, giving a change of about 108 for each step is much closer than the 128 change that a range that includes over-range would give.
 

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