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TTL signal to analog waveform
mujat@my-deja.c
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06-19-2000 08:44 AM
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I want to read the signal from a photomultiplier (TTL signal 3V, 9ns
wide pulses) and convert the reading into an analog waveform
proportional to the intensity of the light incident on the
photomultiplier.
The number of pulses given by the photomultiplier unit is directly
proportional to the intensity of the incident light (which varies more
or less sinusoidal with a frequency of about 50kHz).
I have a DAQ PCI-MIO-16E-1, and LabView 5.1.
I assume I have to use a counter input, to count the number of pulses,
but I don't know how to convert the output of the counter.vi into an
analog waveform.
Anybody has a clue?
Than you in advance.
Mircea
Sent via Deja.com http://www.deja.com/
Before you buy.
wide pulses) and convert the reading into an analog waveform
proportional to the intensity of the light incident on the
photomultiplier.
The number of pulses given by the photomultiplier unit is directly
proportional to the intensity of the incident light (which varies more
or less sinusoidal with a frequency of about 50kHz).
I have a DAQ PCI-MIO-16E-1, and LabView 5.1.
I assume I have to use a counter input, to count the number of pulses,
but I don't know how to convert the output of the counter.vi into an
analog waveform.
Anybody has a clue?
Than you in advance.
Mircea
Sent via Deja.com http://www.deja.com/
Before you buy.
Dr. Holger Hofmann
Member
06-22-2000 07:36 AM
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To get the possible working range of the method you proposed: First a short
calculation of timescales and
accuracies.
I assume you would like to measure the shape of the sinusoidal light intensity
variation.
Taken 12 sample points for one period of intensity wave, this means 1.67
us per sample.
To get an accuracy of 10%, you will need 100 counts per sample intervall.
This gives 16.7 ns
mean time per light puls. The MIO counters run at maximum 20 MHz. This means
50 ns per puls.
So this can only work with reduced accuracy (down to 30% or so) and only
8 points per sine.
All this only makes sense if you do not have any puls pile up on the PMT.
I assume your PMT-unit
works in single photon counting mode and light intensities are low.
My recommended approac
h would be: analogous integration of the TTL-pulses
and then analog input with the PCI-MIO card.
Hope this can help.
Holger
mujat@my-deja.com wrote:
>I want to read the signal from a photomultiplier (TTL signal 3V, 9ns>wide
pulses) and convert the reading into an analog waveform>proportional to the
intensity of the light incident on the>photomultiplier.>The number of pulses
given by the photomultiplier unit is directly>proportional to the intensity
of the incident light (which varies more>or less sinusoidal with a frequency
of about 50kHz).>I have a DAQ PCI-MIO-16E-1, and LabView 5.1.>I assume I
have to use a counter input, to count the number of pulses,>but I don't know
how to convert the output of the counter.vi into an>analog waveform.>>Anybody
has a clue?>>Than you in advance.>Mircea>>>Sent via Deja.com http://www.deja.com/>Before
you buy.
calculation of timescales and
accuracies.
I assume you would like to measure the shape of the sinusoidal light intensity
variation.
Taken 12 sample points for one period of intensity wave, this means 1.67
us per sample.
To get an accuracy of 10%, you will need 100 counts per sample intervall.
This gives 16.7 ns
mean time per light puls. The MIO counters run at maximum 20 MHz. This means
50 ns per puls.
So this can only work with reduced accuracy (down to 30% or so) and only
8 points per sine.
All this only makes sense if you do not have any puls pile up on the PMT.
I assume your PMT-unit
works in single photon counting mode and light intensities are low.
My recommended approac
h would be: analogous integration of the TTL-pulses
and then analog input with the PCI-MIO card.
Hope this can help.
Holger
mujat@my-deja.com wrote:
>I want to read the signal from a photomultiplier (TTL signal 3V, 9ns>wide
pulses) and convert the reading into an analog waveform>proportional to the
intensity of the light incident on the>photomultiplier.>The number of pulses
given by the photomultiplier unit is directly>proportional to the intensity
of the incident light (which varies more>or less sinusoidal with a frequency
of about 50kHz).>I have a DAQ PCI-MIO-16E-1, and LabView 5.1.>I assume I
have to use a counter input, to count the number of pulses,>but I don't know
how to convert the output of the counter.vi into an>analog waveform.>>Anybody
has a clue?>>Than you in advance.>Mircea>>>Sent via Deja.com http://www.deja.com/>Before
you buy.
