HP 3478A Technical Manual Download

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TM 11-6625-3071-14

3478A

defines the state. The following lists the home
commands and the corresponding operating states.

HO Command.

The instrument state for this command

is as follows:

Function ................................................... DCV (F1)
Range..................................... 30mV, Auto (R-2RA)
Trigger...................................................... Hold (T4)
Number of Digits Displayed.................... 4 1/2 (N4)
Autozero......................................................On (Z1)

In addition, the 3478A’s External Trigger is disabled and
the instrument is set into the lowest range (R-2) before
Autorange is selected. Also, any data (reading) output to
the Bus or the front panel is erased when the home
command is sent. The corresponding program codes of
the instrument state are: "FIT4R-2RAZIN4".

b. HI Command (DCV).

This command is the same

as the "HO” command, except a trigger occurs and the
resultant output can be read. The corresponding
program codes are: "FIR-2RAZIN4T3".

c. H2 Command (ACV).

The same as the "HI"

command, except the selected function is AC Volts. The
corresponding program codes are: "F2R-2RAZIN4T3".

d. H3 Command (2-Wire Ohms).

Same as the "HI"

command, except the selected function is 2-Wire Ohms.
The corresponding program codes are: "F3R-
2RAZIN4T3".

e. H4 Command (4-Wire Ohms).

Same as the "HI"

command, except the selected function is 4-Wire Ohms.
The corresponding program codes are: "F4R-2RAZ
1N4T3".

f. H5 Command (DCI).

Same as the "HI" command,

except the selected function is DC Current. The
corresponding program codes are: "F5R-2RAZIN4T3".

g. H6 Command (ACI).

Same as the "Hi" command,

except the selected function is AC Current. The
corresponding program codes are: "F6R-2RAZIN4T3".

h. H7 Command (Ext. Ohms).

Same as the "Hl”

command, except the selected function is Extended
Ohms (see paragraph 3-118). The corresponding
program codes are: "F7R-2RAZIN4T3".

3-111. Reading Data from the 3478A. Data in the form
of readings can be output by the 3478A over the HP-IB
(other data that can be output is discussed in later
paragraphs). To output a reading (if available), the
3478A has to be addressed to "talk". The readings are
output using 13 ASCII characters and are in the following
form:.

3-112. Each character in the output statement (except
EOI) is one byte, which adds up to 13. The exponent will
be in engineering notation (E-3, E+0, E+3, or E + 6) and
the mantissa will always have I, 2, or 3 digits before the
decimal point (D.DDDDD, DD.DDDD, or DDD.DDD). If
the 3478A is in the 4 1/2 or 3 1/2 Digit mode, the 5th
and/or 6th digits will be output as zeroes. An overload
condition (whether plus or minus) will be output as: +
9. 9. If a different output is requested (Binary,
Front/Rear Switch position, etc.), the other output
supersedes the reading. If a data transfer is interrupted
while being output, the 3478A continues the output
wherever it left off, when addressed again. This partial
output (or any output) can be disabled by a Group
Execute Trigger (GET), Clear Message (DCL or SDC),
sending any valid program code, or pressing the LOCAL,
Shift, and TEST/RESET buttons on the front panel. 3-
113. Front/Rear Switch Position. The 3478A's
Front/Rear Switch position can be remotely determined
by sending program code "S" to the multimeter and then
reading its output. If "0" (CR LF) is output the switch is
set to Rear, and if "1" (CR LF) is output the switch is set
to Front.

3-114. Data Ready Feature. The Data Ready feature
of the 3478A, when enabled, outputs a Require Service
Message (SRQ) after each completed measurement
cycle. Before the message can be output, bit 0 of the
SRQ Mask must be set. This is done by sending
program code "M01" (bit 0 of the Status Byte and Status
Register). When the Require Service Message is sent,
the front panel "SRQ" annunciator turns on and bit 0 of
the Status Byte is set. The SRQ condition remains until
the data is read by the controller, or a Serial Poll is done.

3-115. Front Panel SRQ. The Front Panel SRQ feature
of the 3478A outputs a Require Service Message (SRQ)
each time the Front Panel SRQ button is pressed. Before
the message can be output, bit 4 of the SRQ Mask must
be set. This is done by sending program code "M20" (bit
4 of the Status Byte and Status Register). Once this is
done, the Require Service Message will be output and
the front panel SRQ annunciator turns on, whenever the
SRQ button is pressed. The SRQ condition remains until
a Serial Poll is done by the controller.

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