1734-vhsc24

Did you leave the encoder set to 200ppr?

Also possible that it was a lucky capture. If you have 1mm window and you're skipping every 8.6mm, then what, like 12% chance of getting it anyway?

It seems you have all the math now. Start from scratch with the math ad make sure you are programming and configuring everything to ensure you don't miss. Maybe program in error handling code for when you do miss the window, for example comms loss for 10ms.

AustralIan said:

... a 1MHz VHSC samples the signal every nanosecond,...

Click to expand...

(newbie trying to follow this thread).


you meant microsecond, right?

drbitboy said:

(newbie trying to follow this thread).


you meant microsecond, right?

Click to expand...

Haha, yes! Millisecond. In fact if it is rated for 1MHz signals, it probably samples slightly faster than that.

Trying to understand the process

vinigusto said:

For a period of 1 ms, a missed pulse rate would be: Freq = (1000PPRx2600RPM) / 60 ~ = 43.33 KHz. Thus 43.33 KHz * 0.001 ms ~ = 43.33 Pulses equivalent to 8.6 mm.

Click to expand...

Still a newbie trying to follow the thread and learn summat; I understand the math, it's basically multiplying by 1, like 90% of engineering, but I have a few queries:


You meant 3600RPM, not 2600RPM, so 12mm, is that correct (and ~6mm at 1750RPM)?




Does the following describe the process?

• A defective discrete part triggers a failure at inspection station X
• Record the current conveyor position, "Pfail," via [counter+encoder],
  • Triggered by defective part inspection event above
• Calculate the future conveyor position when defective part will reach expulsion diverter:

• • Pdivert = Pfail + [known diverter position] - [known station X position]

• Monitor conveyor position over time, and
  • Trigger diverter when conveyor position is within some +/- range of Pdivert
    • This is the GRT/LES test referred to?
    • And the problem is that sometimes the measured conveyor position jumps over the [Pdivert +/- range] values?

Does "RPI" mean Request Packet Interval, i.e. how often encoder sends position to PLC, or how often PLC requests position from encoder?


What is a typical distance between each part, defective or not?


What is the defect rate?


These are a lot of questions, thanks in advance for considering a response.

AustralIan said:

Did you leave the encoder set to 200ppr?

Click to expand...

I am working with 200 PPR now

Also possible that it was a lucky capture. If you have 1mm window and you're skipping every 8.6mm, then what, like 12% chance of getting it anyway?

AustralIan said:

It seems you have all the math now. Start from scratch with the math ad make sure you are programming and configuring everything to ensure you don't miss. Maybe program in error handling code for when you do miss the window, for example comms loss for 10ms.

Click to expand...

I do not understand this part: "Maybe program in error handling code for when you do miss the window, for example comms loss for 10ms".

drbitboy said:

Still a newbie trying to follow the thread and learn summat; I understand the math, it's basically multiplying by 1, like 90% of engineering, but I have a few queries:


You meant 3600RPM, not 2600RPM, so 12mm, is that correct (and ~6mm at 1750RPM)?




Does the following describe the process?

• A defective discrete part triggers a failure at inspection station X
• Record the current conveyor position, "Pfail," via [counter+encoder],
  • Triggered by defective part inspection event above
• Calculate the future conveyor position when defective part will reach expulsion diverter:

• • Pdivert = Pfail + [known diverter position] - [known station X position]

• Monitor conveyor position over time, and
  • Trigger diverter when conveyor position is within some +/- range of Pdivert
    • This is the GRT/LES test referred to?
    • And the problem is that sometimes the measured conveyor position jumps over the [Pdivert +/- range] values?

Does "RPI" mean Request Packet Interval, i.e. how often encoder sends position to PLC, or how often PLC requests position from encoder?


What is a typical distance between each part, defective or not?


What is the defect rate?


These are a lot of questions, thanks in advance for considering a response.

Click to expand...

1 - I meant even 2600 RPM.

2 - Exactly


3 - The RPI of the I / O cards is set to 1 ms (minimum possible). VHSC24 card RPI is in 2 ms (minimum possible too)

4 - It is around 200 250 mm.


5 - I have no way to need it, varies greatly.

AustralIan said:

Did you leave the encoder set to 200ppr?

Also possible that it was a lucky capture. If you have 1mm window and you're skipping every 8.6mm, then what, like 12% chance of getting it anyway?

It seems you have all the math now. Start from scratch with the math ad make sure you are programming and configuring everything to ensure you don't miss. Maybe program in error handling code for when you do miss the window, for example comms loss for 10ms.

Click to expand...

Using a periodic 1 ms task, can you really? In practice, it turned out to be, but what would the calculation be?