Comments 1. Digitizer Configuration. Both channel’s HI differential inputs (ports 3 and 4) are CONFigured for 10 readings on the 5V range. Two readings (channel 1 and channel 2) are taken on each sample trigger. The sample rate, as set by the CONFigure command, is 50 ns (20 MHz). Thus, data is transferred at a rate of 40 MSamples (80 MBytes)/second.

Before setting the digitizer’s Local bus configuration the Local bus chip is reset. Next, the Local bus mode is set to GENerate and the feed (data source) is set to CONVerter:BOTH.

2.Post-Arm Readings. When transferring readings over the Local bus from the digitizer A/D, all readings must be post-arm.

3.Initiating the Digitizer. After the memory card is configured, it is INITiated first so that it is ready to receive the digitizer readings. When the digitizer is INITiated, *OPC? is used to allow the readings to complete and be transferred before they are retrieved from the memory card.

4.Reading Sequence and Format. When this program executes, the readings are transferred to the memory card and later displayed in the following sequence:

channel 2 reading 1 channel 1 reading 1 channel 2 reading 2 channel 1 reading 2

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The memory card was set up to store the readings in the digitizer’s packed data format. The packed readings are signed, 16-bit numbers preceded by the ANSI/IEEE Standard 488.2-1987 Definite Length Arbitrary Block header. Packed readings are always numbers between -1.0230 (-2046) and +1.0235 (2047). To convert the readings to voltages, each reading is divided by 16 to remove the data label bits (0 - 3), and is multipled by 0.0025 which is the reading resolution for the 5V range.

5.Additional Information. Additional information on Local bus operation and on the Local bus commands can be found in Chapter 3 - "Understanding the Digitizer", and in Chapter 4 - "Command Reference."

Chapter 2

Using the Digitizer 87

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HP E1429A manual Chapter Using the Digitizer