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I am trying to create a project and I am running into a few roadblocks. I need to record a pressure every 2mS and record it to the SD card. I have a 16GB card so I should be able to record a ton of data, all I need to record is a 4-digit MI value. My problem is writing the data to the SD card. What is the best way to do this?

Currently I am trying to do it in pulses. Step 1) for the first 5sec I record my value every 2mS with an indirect store. Step 2) for the next 25sec I want to write this vector of values to the SD card. Step 3) Rinse and repeat.

What would be the best way to record tthe vector to the SD card?

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I am trying to create a project and I am running into a few roadblocks. I need to record a pressure every 2mS and record it to the SD card. I have a 16GB card so I should be able to record a ton of data, all I need to record is a 4-digit MI value. My problem is writing the data to the SD card. What is the best way to do this?

Currently I am trying to do it in pulses. Step 1) for the first 5sec I record my value every 2mS with an indirect store. Step 2) for the next 25sec I want to write this vector of values to the SD card. Step 3) Rinse and repeat.

What would be the best way to record tthe vector to the SD card?

Someone may correct me if I am wrong, but I think 4GB is the largest SD memory that the Unitronics will recognize. So even with a 16gig card your still bumping into that 4gig limit.

2mS is pretty fast. What is your scan time? What OPLC are you using? You probably want something with the fastest CPU like the V570.

Does your 2mS need to be precise, or can you cope with just sampling it every scan?

One trick you can do to keep things linear is to use the interval timer to time stamp the interval between each sample. This way when you chart things out in for example excel you can plot against your time interval axis.

Also leep in mind, at 2mS the instrumention and the electronics reading that instrumentation is probably not fast enough to be giving you realistic data at that rate. Depending on what hardware you are using to read the values in (I am assuming analog) the unitronics modules all have varying degrees of update rates from one product to the next. Before you go too fat down the programming path you may wish to verify that your hardware is capable of the response times you require.

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The Unitronics will recognize a larger SD, but remember that the largest size file that is supported under windows is 4 Gig, so after that you need to create a new file.

Hi TM, thanks for the correction on the SD card and the Unitronics.

On a side note......

Isn't the 4Gig thing more to do with FAT32 than windows? I have plenty of files in windows over 4GB in size under NTFS. My outlooking.pst file being the largest.

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Someone may correct me if I am wrong, but I think 4GB is the largest SD memory that the Unitronics will recognize. So even with a 16gig card your still bumping into that 4gig limit.

2mS is pretty fast. What is your scan time? What OPLC are you using? You probably want something with the fastest CPU like the V570.

Does your 2mS need to be precise, or can you cope with just sampling it every scan?

One trick you can do to keep things linear is to use the interval timer to time stamp the interval between each sample. This way when you chart things out in for example excel you can plot against your time interval axis.

Also leep in mind, at 2mS the instrumention and the electronics reading that instrumentation is probably not fast enough to be giving you realistic data at that rate. Depending on what hardware you are using to read the values in (I am assuming analog) the unitronics modules all have varying degrees of update rates from one product to the next. Before you go too fat down the programming path you may wish to verify that your hardware is capable of the response times you require.

I am using a V130 and my scan time says 2mS so I am just recording every scan. I am hoping to catch a pressure increase as the flight of a screw rotates in front of an injection port, which at 60rpm looks to be around 100mS so we are hoping to catch some good numbers "over time" which is why we want to grab so many samples.

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