Fluke PM6681 General Speed Improvements, Block Synchronized Measurements, READARRay?, MEASARRay?

How to Measure Fast

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.

￿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.

￿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?￿3 fetches result two, three, and four.

￿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 120∝s ( PM6681 ).

General Speed Improvements 7-7