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Technical Discussions
Pim van Andel
Pim van Andel
04:11 Jun-02-1998
pulse repetition frequency

I am working on the design for electronics of a PC based ultrasonic
instrument.

For manual weld inspection the pulse repetition rate must be rather high
(250Hz?) in view of the probe speed (150mm/sec) and the requirement that
you do not want to miss defect echos. The problem is that a PC screen
can only display A-scans at a rate of e.g. 20 A-scans/sec.

My question: How to reduce 250 Hz prf to 20 A-scans/sec; how is this
solved in digital UT instruments?

Eugene Suchcicki
Eugene Suchcicki
02:25 Jun-03-1998
Re: pulse repetition frequency
My private( I am not an expert in this field) it would
be to make "average" of let say 25 scans and calculate
one PC screen of information. This "average" could be
inteligent enough to represent miningfull data.
In its simplest form it could be just average.
But having 25 sets of data to be reperented by "one"
event you could for example display such values as
1. min
2. max
3. average
The other alternative is to make the probe movment slower
to match speed( refresh rate) of PC screen. But even so
can anyone spot the problem on the screen if the refresh
rate is high (and probe speed is high). ( Actual information
is on the sceen for fraction of a sec only)
So real time data on the PC screen is of little benefit.
More static screen with recalculated(evaluated)data is what
I would aim for.

: I am working on the design for electronics of a PC based ultrasonic
: instrument.

: For manual weld inspection the pulse repetition rate must be rather high
: (250Hz?) in view of the probe speed (150mm/sec) and the requirement that
: you do not want to miss defect echos. The problem is that a PC screen
: can only display A-scans at a rate of e.g. 20 A-scans/sec.

: My question: How to reduce 250 Hz prf to 20 A-scans/sec; how is this
: solved in digital UT instruments?

Rainer Meier
R & D
retired from intelligeNDT Systems & Services, Germany, Joined Nov 1998, 15

Rainer Meier

R & D
retired from intelligeNDT Systems & Services,
Germany,
Joined Nov 1998
15
02:46 Jun-03-1998
Re: pulse repetition frequency
: I am working on the design for electronics of a PC based ultrasonic
: instrument.

: For manual weld inspection the pulse repetition rate must be rather high
: (250Hz?) in view of the probe speed (150mm/sec) and the requirement that
: you do not want to miss defect echos. The problem is that a PC screen
: can only display A-scans at a rate of e.g. 20 A-scans/sec.

: My question: How to reduce 250 Hz prf to 20 A-scans/sec; how is this
: solved in digital UT instruments?

For my opinion, it is very important to avoid the suppression of relevant
data. Therefore I would suggest, to show a kind of envelope of the A-scans,
that means to view at each point of time of flight the maximal as well
as the minimal amplitude.
Advandages: - No significant information lost
UT-result at your component: The speed is slow enough,
if there is only a small difference bedween minimum
and maximum amplitude.

Rainer Meier

Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
01:18 Jun-03-1998
Re: pulse repetition frequency
: For manual weld inspection the pulse repetition rate must be rather high
: (250Hz?) in view of the probe speed (150mm/sec) and the requirement that
: you do not want to miss defect echos. The problem is that a PC screen
: can only display A-scans at a rate of e.g. 20 A-scans/sec.
The alarm suppose to be automated in order not to miss echoes.

: My question: How to reduce 250 Hz prf to 20 A-scans/sec; how is this
: solved in digital UT instruments?
As already was mentioned, use minimal, maximal,average or trailing envelope
of desired number of A-scans.

rysiek
rysiek
01:42 Sep-01-1999
Re: pulse repetition frequency
: My private( I am not an expert in this field) it would
: be to make "average" of let say 25 scans and calculate
: one PC screen of information. This "average" could be
: inteligent enough to represent miningfull data.
: In its simplest form it could be just average.
: But having 25 sets of data to be reperented by "one"
: event you could for example display such values as
: 1. min
: 2. max
: 3. average
: The other alternative is to make the probe movment slower
: to match speed( refresh rate) of PC screen. But even so
: can anyone spot the problem on the screen if the refresh
: rate is high (and probe speed is high). ( Actual information
: is on the sceen for fraction of a sec only)
: So real time data on the PC screen is of little benefit.
: More static screen with recalculated(evaluated)data is what
: I would aim for.

:
: : I am working on the design for electronics of a PC based ultrasonic
: : instrument.

: : For manual weld inspection the pulse repetition rate must be rather high
: : (250Hz?) in view of the probe speed (150mm/sec) and the requirement that
: : you do not want to miss defect echos. The problem is that a PC screen
: : can only display A-scans at a rate of e.g. 20 A-scans/sec.

: : My question: How to reduce 250 Hz prf to 20 A-scans/sec; how is this
: : solved in digital UT instruments?
POWODZENIA GIENEK

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