3-52
BOP HIPWR 091719
3.4.6
MONITORING OUTPUT CURRENT USING AN ANALOG SIGNAL
The BOP provides an output analog signal, 0 to ±10V, that is proportional to the output current
which is always available. For the master of a parallel or series configuration this signal is pro-
portional to the output current of the parallel or series combination. This signal is available at pin
3, referenced to pin 10, of the Analog I/O port. To protect the BOP circuitry this signal is provided
via a series 2K ohm resistor, thus requiring a high impedance monitoring device or instrument.
3.5
DIGITAL REMOTE MODE PROGRAMMING
BOP models may be digitally programmed over a control bus using SCPI (Standard Commands
for Programmable Instruments). SCPI provides a common language conforming to IEEE 488.2
for instruments used in an automatic test system (see PAR. 3.6). The control bus used must be
either the IEEE 488 standard communication bus (General Purpose Interface Bus, GPIB), or the
RS 232C Serial Bus.
Refer to Table 2-11 for input/output signal allocations for communication via the GPIB, Table 2-5
for RS 232, and Table 2-2 for the BITBUS. All power supply functions available from the keypad
can be programmed via remote SCPI commands. In addition, some features that are not avail-
able from the keypad may be implemented using remote commands (see PAR. 3.5.1).
This section includes a discussion of GPIB bus protocols (PAR. 3.5.4), instructions for changing
the GPIB address (PAR. 3.5.3.2.1), a discussion of the VISA (Virtual Instrumentation Software
Architecture) driver supplied with the unit (PAR. 3.5.5), RS 232C Operation (PAR. 3.5.6), fol-
lowed by a detailed explanation of SCPI programming (PAR. 3.6).
3.5.1
OPERATING FEATURES AVAILABLE ONLY BY REMOTE COMMANDS
The following paragraphs describe features of the BOP that are not available from the front
panel, but can be implemented using remote commands.
3.5.1.1
MEASUREMENT CAPABILITIES
The default measurement functionality continually samples the voltage and current and saves
the samples in an array. Every 16 sample pairs the sample is averaged and compared to the
previous measurement sample. If the new sample is more than a few LSBs different from the
previous one, the new sample and the next sample are provided to both the SCPI processor
and the front panel display. Once a difference from one sample to the next is within a few LSBs
for 64 samples, the average is created for the 64 samples and provided to the SCPI processor
and the front panel display. If the absence of a difference remains for 128 samples, the average
of 128 measurement samples will be provided to the other processors. This time, from the first
detected difference to the 128 average being provided to the unit, is defined as the unit settling
time, and is available in the operating status register as bit 1.
The command MEASure:MODE can modify this settling behavior by changing it to SYNChro-
nous mode. In SYNChronous mode, whenever the main channel set point or the protection lev-
els are changed, the sample pair logic is reset to start a new 16 pair sample. The average of this
sample will be forced to be different than the previous sample value. The measurement system
continues to operate after this sample, providing the 64 and 128 sample averages as required. It
is possible to ensure this first sample is returned by the measure command; paragraph 3.5.1.2.3
describes this in detail.
Summary of Contents for BOP-ME 1KW
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