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Is A PicoLog 1012 Suitable?
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BilloBillo
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- Posts: 4
- Joined: Fri Dec 11, 2020 3:13 am
Is A PicoLog 1012 Suitable?
This is for a PicoLog 1012 logger.
I am sorry for the length of the question, it is difficult without a diagram.
Channel 1 has a sync pulse of about 20 uS width with a notch near the centre of it.
The notch width is about 5 us and the amplitude does not fall to zero.
The sync waveform is not square it has rounded edges.
I want to capture the shape so I assume that is done in Block Mode at 1 million samples per second.
Sampling will be triggered by the leading edge of this sync pulse.
Sampling it at 1 uS between samples will be good enough to see the degree of rounding of the leading and trailing edges and the approximate position and shape of the notch.
Channel 2 has a 100 kHz sine wave.
I want to see the phase of it at the position of the notch in the sync pulse.
It should be a negative going crossover.
Q1 -
Because 2 channels are used will the sampling rate still be 1 uS or will it be divided between the channels and be reduced to 2 uS?
Q2 -
Is this correct?
The 8k internal buffer receiving data from 2 channels will contain 4k samples from each channel.
So the sync channel will have the sync waveform and the remainder being zero and 4k samples of the channel 2 sine wave, ie about 2 cycles during the sync waveform and the remainder being the 100 kHz waveform.
Two cycles during the sync waveform will make it easy to see the phase relationship.
Q3 -
Which application should I use, PicoLog or PicoScope?
Thank you for your advice.
Bill
I am sorry for the length of the question, it is difficult without a diagram.
Channel 1 has a sync pulse of about 20 uS width with a notch near the centre of it.
The notch width is about 5 us and the amplitude does not fall to zero.
The sync waveform is not square it has rounded edges.
I want to capture the shape so I assume that is done in Block Mode at 1 million samples per second.
Sampling will be triggered by the leading edge of this sync pulse.
Sampling it at 1 uS between samples will be good enough to see the degree of rounding of the leading and trailing edges and the approximate position and shape of the notch.
Channel 2 has a 100 kHz sine wave.
I want to see the phase of it at the position of the notch in the sync pulse.
It should be a negative going crossover.
Q1 -
Because 2 channels are used will the sampling rate still be 1 uS or will it be divided between the channels and be reduced to 2 uS?
Q2 -
Is this correct?
The 8k internal buffer receiving data from 2 channels will contain 4k samples from each channel.
So the sync channel will have the sync waveform and the remainder being zero and 4k samples of the channel 2 sine wave, ie about 2 cycles during the sync waveform and the remainder being the 100 kHz waveform.
Two cycles during the sync waveform will make it easy to see the phase relationship.
Q3 -
Which application should I use, PicoLog or PicoScope?
Thank you for your advice.
Bill
Re: Is A PicoLog 1012 Suitable?
Hi Bill,
To answer your questions:
1/ Yes, the sample rate would be divided among the active channels (to the nearest power of 2 if you were using more than two).
2/ Yes, when using block mode the data has to be captured in the hardware buffer, so the memory available for sample data will be halved between the channels, and your calculations are correct regarding what you will capture.
3/ You should use PicoScope 6 as PicoLog 6 doesn't have a block Mode (or Fast Sampling Mode).
However, you mention a sinewave, with a negative phase that you want to see. As the PicoLog 1012 is single ended, you would need to use offset and scaling to transform the sinewave into a positive only waveform. Is there any other specific reason why you want to use the PicoLog 1012 because, if 8-bit resolution is sufficient, then a PicoScope (such as the PicoScope 2204A) would be a better choice if you are only capturing those 2 signals (no offset and scaling necessary)?
Regards,
Gerry
To answer your questions:
1/ Yes, the sample rate would be divided among the active channels (to the nearest power of 2 if you were using more than two).
2/ Yes, when using block mode the data has to be captured in the hardware buffer, so the memory available for sample data will be halved between the channels, and your calculations are correct regarding what you will capture.
3/ You should use PicoScope 6 as PicoLog 6 doesn't have a block Mode (or Fast Sampling Mode).
However, you mention a sinewave, with a negative phase that you want to see. As the PicoLog 1012 is single ended, you would need to use offset and scaling to transform the sinewave into a positive only waveform. Is there any other specific reason why you want to use the PicoLog 1012 because, if 8-bit resolution is sufficient, then a PicoScope (such as the PicoScope 2204A) would be a better choice if you are only capturing those 2 signals (no offset and scaling necessary)?
Regards,
Gerry
Gerry
Technical Specialist
Technical Specialist
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BilloBillo
- User
- Posts: 4
- Joined: Fri Dec 11, 2020 3:13 am
Re: Is A PicoLog 1012 Suitable?
Hi Gerry,
Thank you very much for your detailed answers.
The question was for an initial acceptance test by my customer.
I will reply to both my topics in each one so a forum member who only reads one will see the complete situation.
I considered using the 1012 logger because of the number of channels.
Thank you for suggesting the PicoScope 2204A, unfortunately 10 channels are eventually required but I will inform the user that only 8 are possible and I will quote for using a PicoScope 4824.
I will also quote for designing and building a 10 channel logger with A-D and buffers in each channel and all channels driven by a common clock.
The huge cost mainly due to including precision channel amplifiers, etc will make the PicoScope 4824 seem inexpensive.
My reason for wanting to align the channel data is that the user is smart enough to see the misalignment (in a table or charts) and say something like "while one channel is being sampled the state of the other channels are unknown" and will reject that data and the whole logging system.
By cheating and making the data appear to be aligned the data will be accepted and the tiny notional errors will still be there but will not be anywhere near significant.
I know what is needed and it is nothing like what has been specified.
I suppose you have experience with people dreaming up specifications without understanding what they mean and what is required to achieve them.
Thanks again for your help.
Thank you very much for your detailed answers.
The question was for an initial acceptance test by my customer.
I will reply to both my topics in each one so a forum member who only reads one will see the complete situation.
I considered using the 1012 logger because of the number of channels.
Thank you for suggesting the PicoScope 2204A, unfortunately 10 channels are eventually required but I will inform the user that only 8 are possible and I will quote for using a PicoScope 4824.
I will also quote for designing and building a 10 channel logger with A-D and buffers in each channel and all channels driven by a common clock.
The huge cost mainly due to including precision channel amplifiers, etc will make the PicoScope 4824 seem inexpensive.
My reason for wanting to align the channel data is that the user is smart enough to see the misalignment (in a table or charts) and say something like "while one channel is being sampled the state of the other channels are unknown" and will reject that data and the whole logging system.
By cheating and making the data appear to be aligned the data will be accepted and the tiny notional errors will still be there but will not be anywhere near significant.
I know what is needed and it is nothing like what has been specified.
I suppose you have experience with people dreaming up specifications without understanding what they mean and what is required to achieve them.
Thanks again for your help.
Re: Is A PicoLog 1012 Suitable?
Hi BilloBillo,
Thanks for your explanation. and I'm glad you have what you need to respond to your customer.
Just as an aside, there is never any need to 'cheat' the customer. For data logging, the data needs to be aligned because the purpose of collecting it is for making comparisons. If relative channel timing is important, the misalignment (1us of clock skew between the channels) can be legitimately explained as the timing error between channels. The significance of this, and how it will affect the measurement application can then be debated.
In data logging applications (which is what the PicoLog 1000 series devices were designed for) it is typically the overall sample rate that it is more important. So, for instance, a customer will be typically less concerned that when sampling on all 12 channels of the PicoLog 1012, channel 12 will be skewed 12us from channel 1, rather than the fact that the minimum effective sample interval on any single channel will be 16us (which would be more important in your customers case, as he wouldn't have the 1us effective sample rate per channel that you were referring to originally, if he's using all of the inputs).
Yes, we do get some 'interesting' requirements, however, that's what this Forum is for, as not everyone has the benefit of the knowledge that you've acquired
.
Regards,
Gerry
Thanks for your explanation. and I'm glad you have what you need to respond to your customer.
Just as an aside, there is never any need to 'cheat' the customer. For data logging, the data needs to be aligned because the purpose of collecting it is for making comparisons. If relative channel timing is important, the misalignment (1us of clock skew between the channels) can be legitimately explained as the timing error between channels. The significance of this, and how it will affect the measurement application can then be debated.
In data logging applications (which is what the PicoLog 1000 series devices were designed for) it is typically the overall sample rate that it is more important. So, for instance, a customer will be typically less concerned that when sampling on all 12 channels of the PicoLog 1012, channel 12 will be skewed 12us from channel 1, rather than the fact that the minimum effective sample interval on any single channel will be 16us (which would be more important in your customers case, as he wouldn't have the 1us effective sample rate per channel that you were referring to originally, if he's using all of the inputs).
Yes, we do get some 'interesting' requirements, however, that's what this Forum is for, as not everyone has the benefit of the knowledge that you've acquired
.Regards,
Gerry
Gerry
Technical Specialist
Technical Specialist