5/21/2015 4:13 PM | |
Posts: 15 Rating: (0) |
Hello Everyone, I am using a AI module (SM 1231) with CPU 1212C DC/DC/DC for a distance measurement project. I am using a Draw wire sensor from Kubler. The sensor has a output of 0V (at 0 meters) to 10V (at 1 meter). I am reading out the sensor value but I don't understand the followings. 1. AI module states that it is a 13 bit A/D converter, so I expect at 1V sensor output it would give a reading of 8191 but instead it gives a value around 27648. How can a 13 bit A/D converter give such high value?
2. Every time I pull the wire from the sensor the output changes but the change in output is very slow. Is there a way to solve this problem? What is causing this delay? I tried increasing the integration time from 50 Hz to 400 Hz but still the response time is not fast enough. Any suggestion is highly appreciated. |
5/21/2015 10:31 PM | |
Joined: 7/7/2010 Last visit: 9/20/2024 Posts: 15213 Rating: (2417)
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1. 27648 (base 10) = 0x6C00 = 0b1101 1000 0000 0000. This thread may help explain it: https://support.industry.siemens.com/tf/ww/en/posts/how-27648-analaog-maximum-value/26057/?page=0&pageSize=10
2. Look at your channel smoothing value. If it is too slow, change it to None rather than 4 (the default).
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science guy |
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5/22/2015 8:57 AM | |
Posts: 15 Rating: (0) |
Hi Huggy, I tried changing the channel smoothing value to None but it doesn't seem to help. Any other way to improve the A/D converter response?
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5/26/2015 3:22 PM | |
Joined: 7/7/2010 Last visit: 9/20/2024 Posts: 15213 Rating: (2417)
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You can try reading it manually every 2 ms by creating an OB that runs every 2 ms, and reads directly from the analog input.
Let's say for example the analog input is IW64. In your 2 ms OB, you read it by referencing like this: IW64:P Do not do much in the OB or it will cause the OB to stop working properly and generate a lot of diag buffer messages.
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science guy |
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This contribution was helpful to1 thankful Users |
5/26/2015 3:23 PM | |
Joined: 7/7/2010 Last visit: 9/20/2024 Posts: 15213 Rating: (2417)
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If you need faster still, you need a faster PLC system or a PC based data AQ. |
science guy |
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