Scanning a Range of Switchbox Channels

Example: MakingVoltage Measurementsby Scanning

You can scan a range of channels of a switchbox consisting of single or multiple multiplexer modules. Scanning involves sequentially closing each channel on a range of specified channels. The selected TRIGger mode determines when the channel closure will advance. During scanning, the FET which was previously closed opens before the next FET closes.

You can use any of the TRIGger modes to advance the channel list. TRIGger:SOURce EXTernal requires an external trigger source to be connected to the HP E1300/1301 Mainframe "Event In" port. For computer controlled or HP-IB triggering (TRIGger or *TRG) use TRIGger:SOURce BUS. The OUTput ON command enables the mainframe’s "Trig Out" port to synchronize multimeters when not in the TRIGger:SOURce DBUS IMM modes.

For the fastest scan rate (up to 100 K switches/sec.) use TRIGger:SOURce DBUS. Use a custom cable (see “ Di gital Bus and Triggering” on page 15) to connect the multimeter handshake lines (Voltmeter Complete and External Trigger) to the multiplexer digital bus.

Figures 3-4 and 3-5, and the following commands, show how to make voltage measurements by performing a single scanning cycle of all channels on two multiplexer modules in a single switchbox. In the example, the:

∙A Tree Terminals of each terminal module connect to each other and to the multimeter in Figure 3-5. To connect the A tree terminals to each other, use either the analog bus cables (shown in Figures 2-10 and 2-11) or wire the terminals together between the terminal modules.

∙HP-IB Bus trigger command advances the switchbox channel list.

∙HP E1300A/E1301A Mainframe’s "Trig Out" pulse synchronizes the switchbox with the multimeter.

∙Multimeter HP-IB select code is 7 and primary address is 22.

∙Switchbox HP-IB select code is 7, the HP-IB primary address is 09, and the HP-IB secondary address is 14.

∙Computer is an HP Series 200/300 Computer with HP BASIC using HP-IB.

Enter and Execute:

10

OUTPUT 722;"TRIG EXT;DC 10"

!Sets multimeter to external

 

 

triggers and to measure dc volts

20

OUTPUT 70914;"OUTP ON"

!Enables "Trig Out" port

30OUTPUT 70914;"TRIG:SOUR BUS" !Sets switchbox to receive bus triggers

40OUTPUT 70914;"SCAN:MODE VOLT"!Setup switchbox to measure voltage

50OUTPUT 70914;"SCAN:PORT ABUS"!Closes the appropriate tree isolation switches while scanning; automatically makes connection to the analog bus and tree terminals.

36 Using the HP E1351A/53A FET Multiplexer Modules

Chapter 3