Hameg HO88, Manual

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Sous réserve de modifications / Reservado el derecho de modificación
so, unscrew the 6 screws on the rear panel of the instrument and take off the plastic
back cover; the enclosure can then be pulled off towards the back. Looking at the
instrument from the back, the interface card is installed in the upper right corner of
the instrument, with its component side facing down. The interface card is attached
using the 3 supplied self-tapping screws.
First, however, the two cables for power supply and data transfer are inserted into the
corresponding flat socket connectors on the circuit board of the instrument. The short
cable is the power supply for the interface. The longer cable connects the interface
card with the electrically isolated serial interface of the instrument itself. The enclosure
is then slid back on. When doing so make sure that the edges of the metal enclosure
slide exactly into the grooves of the plastic covers on the front and back. After the
rear plastic cover has been replaced and fastened, the unit is again ready for operation.
Specifications
Connector: Standard 24-pin IEEE-488 connector:
Amphenol Series 57 MICRORIBBON
Output: Open collector
Output voltage levels: High: 2.5V
Low: 0.4 V at 48 mA
Input voltage levels: Typical hysteresis: 0.8V
Input, high: 2.0V
Input, low: 0.6V
Terminations: 3.3 k
Ω
+ 5% (+5 V)
6.2 k
Ω
+5% (ground)
Capacitance : 100pF
Supply voltage: 9.36 V AC
Current consumption: 250 mA
All data and signal lines are electrically isolated from ground (even after installa-
tion in a Series HM8100 instrument)! When the IEEE-488 cable is unconnected-
there is no electrically conductive path to the instrument chassis or the grounded
wire of the power supply!
Address selection
All instruments connected to an IEEE488 bus must receive unique device addresses.
This is done using the 5 DIP switches to the left of the IEEE488 bus connector on the
instruments rear panel. The switches are binary-coded. All addresses are allowed
except decimal 31 (binary 11111). If the switches are set to 11111, this has the effect
of defining Talk-only mode. This mode is selected if it is wished for measurement data
to be output directly, i.e. without the use of a controller. It may be wished, for example,
to directly connect an instrument (Talk-only) with a printer (listen-only). The printer
then continuously prints out the measurement data received from the counter. The
Talk-only mode must never be used in bus configurations incorporating, a Controller,
since the instrument is then unable to „listen to“ the Controller and consequently
cannot be given instructions. If an instrument is accidentally set to Talk-only mode it
will monopolize the bus and interfere with commands issued by the Controller and/or
data on the bus coming from other instruments.
Interface attributes
Not all messages must be decoded by every device. Interface messages are only
decoded If an instrument is properly equipped to do so. Devices that only have Listener
capabilities, for example, do not decode Talker addresses. So-called subset ratings
are used to indicate the capabilities of a given instrument for decoding interface mes-
sages. The IEEE488 standard divides the interface into twelve basic functions, each
of which has a set of options that can be used to implement different subsets of these
capabilities. For example, the specifications for an IEEE-488 interfaceable device might
list the subset functions it supports as SH7, AM1, T5, L3, RL1, DC1, SR1 and C0. The
letter or letters stand for the basic interface functions, and the following digit for the
subset. In each case, a zero indicates that the corresponding capability is not given.