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the counter by yourself. This is primarily
why we recommend the READ? query.
Block Synchronized
Measurements
In the block synchronized mode, the con
-
troller only starts a sequence of measure
-
ments. The counter then measures,
without any controller intervention, at the
highest possible speed. It “dumps” the re
-
sults into internal memory and reads them
out for evaluation later. This method
gives the highest possible data capture
speed.
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READ:ARRay?
This is the basic method for starting up a
measurement sequence and reading the
data. Set up the counter using CONFigure
or individual programming commands
before sending the READ:ARRay?
query. This method will make the mea-
surements with a high measurement rate.
The speed depends on a number of indi-
vidual measurement parameters; see also
“General speed improvements” below.
The counter stores the data in its internal
memory and when it has captured all
data, it transfers the resulting array to the
controller.
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INIT + GET + FETCH:ARRay?
The READ:ARRay? method has one
drawback, it includes some unwanted
firmware overhead between when the
counter receives the command and it
starts the first measurement. This can be
solved by setting up the counter to wait
for a GET before it starts the measure
-
ment sequence. The default actions for
GET include sending a single result ( the
first value) when the counter has com
-
pleted the sequence. This makes it possi
-
ble to let the controller wait for the Mes
-
sage AVailable status bit to find out when
the data capture is ready. You can read
the complete array by using the
FETCH:ARRay? command. So if, for
example, the array size is 4, GET gives
the first result in the array and
FETC:ARR?83 fetches result two, three,
and four.
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MEAS:ARRay?
The MEASure:ARRay? query ensures
that the measurement sequence is started
after the command is received. It will also
send back the results. It also includes set
-
ting up the counter. This is the command
that has the highest possible degree of
compatibility with other instruments;
however, this command reprograms the
counter and often you need to program
the counter yourself. This is why we rec-
ommend using the READ:ARRay?
query.
General Speed
Improvements
The CNT-8X has many options to im
-
prove measurement speed. Here you will
get a list of actions that you can use to
improve the measurement speed. Most of
these commands decrease the average
dead time. The dead time is the time be
-
tween measurements, that is, from stop to
the next start. These actions are all gen
-
eral, that is, they affect the rate of mea
-
surements for all measurement methods
given above; however, they are especially
valuable for the block synchronized mea
-
surements. In this mode, the dead time
can be as low as 120µs ( PM6681 ).
How to Measure Fast
General Speed Improvements 7-7