HP 8920B, Programmer'S Manual

Page: 72 / 682

72
Chapter 3, HP-IB Command Guidelines
Guidelines for Operation
Reading-Back HP-IB Units.
Use the UNITs? command to read back the current
HP-IB Units setting for a measurement or instrument setup field. For example, the
following BASIC language program statements read back the current HP-IB Units
setting for the
TX Power
measurement:
!Query the current HP-IB Units setting for TX Power.
OUTPUT 714;"MEAS:RFR:POW:UNIT?"
!Enter the returned value into a string variable.
ENTER 714;A$
Guidelines for HP-IB Units
• When setting the value of a numeric field (such as
AFGen1 Freq
), any non–HP-IB
Unit unit-of-measure must be specified in the command string, otherwise the current
HP-IB Unit is assumed by the Test Set.
For example, if the command RFG:FREQ 900 is sent through HP-IB, the Test Set will
interpret the data as 900 Hz, since HZ is the HP-IB Unit for frequency. This would
result in an
Input value out of range
error. Sending the command
RFG:FREQ 900 MHZ would set the value to 900 MHz.
• When querying measurements or settings through HP-IB, the Test Set always returns
numeric values in HP-IB units, regardless of the current Display Unit setting. Numeric
values are expressed in scientific notation.
For example, if the
TX Frequency
measurement is displayed as 150.000000 MHz
on the Test Set, the value returned through HP-IB is 1.5008 (1.5
×
10
8
). Con-
verting the returned value to a format other than scientific notation must be done pro-
grammatically.