Some models are slow to switch meter functions to specific MQs. This was
observed with 34405A and AC V/I modes, where USB connections timed out
and suffered from pipe errors.
Add an optional delay after "CONF:<mode> [<range>]" SCPI requests. The
duration of the delay is per model, the use of the delay is per MQ on
that model. The 200ms delay for 34405A was found by experimentation.
Speaking about 34405A: Only the "INIT" request in temperature mode
remains as an issue, which is not covered by this commit's approach.
Don't use the "[SENS:]<mode>:RANGE..." request on Agilent protocol
speaking devices. Use "CONF:<mode> [<range>]" instead. This was tested
with all devices which reference this model.
In theory there is the question whether previously configured ranges
should be re-used when (exclusively) the MQ is switched. It's assumed
that this is not useful, instead users or their applications should
select the function first and optionally pick the range then. Re-use of
e.g. 10k resistance range when switching to capacitance might be seen as
confusing (and results in errors in the device).
Use the combination of INIT and FETCH? to get measurements. The READ?
request is more complex and might "undo" what INIT already initiated.
This improves perception of the 34405A meter's operation.
While queries for the range are supported for voltage, current,
resistence, capacitance, the same queries in temperature, frequency,
diode, continuity modes not only fail but even lose the USB connection
to the device. This was consistently observed with 34405A and 34465A.
Suppress get and set range requests for the known problematic modes of
the Agilent protocol speaking meters.
Add support to get and set the auto/manual range on Agilent protocol
speaking devices (34405A, 34465A). The range values are mere numbers
without a unit or MQ associated with them. Support to list available
ranges is prepared but not used (not needed on these meters). Common
logic could open code the lists of ranges from the model description
if desired in a future implementation.
The SCPI standard requires OPeration Complete command,
but some Owon meters do not implement it. This commit
makes the probe try OPC once, and if it gets no reply
it assumes it is not supported.
Address minor style issues: Need not assign NULL after g_malloc0(), need
not check for NULL before g_free(). Rephrase diagnostics messages which
are user visible by default, remove internal development details. Reword
a few comments, and adjust their grammar for consistency across the code
base. The sr_analog_init() routine executed immediately before getting
measurements, need not (re-)assign endianess or floating point details,
except those which do change after initialization (double vs float).
Rephrase model dependent checks for easier adjustment during maintenance.
Unobfuscate string comparisons.
The current implementation of the SCPI DMM driver is conservative about
checking the device's being operational, but the *OPC? queries are found
in unfortunate locations. Run the OPC query right before running the
next "actual" command, not afterwards. And certainly not between sending
requests and potentially gathering responses in subsequent calls.
This commit does not change current behaviour, but improves maintenance
before pending commits.
The "get MQ" helper routine communicates SCPI responses and translates
them to internal "MQ and flag" values. Optionally return the MQ table
entry reference to callers, so they don't have to repeat the table
lookup when the function's default precision is required, or should
future "start acquisition" requests need to refer to the meter's current
function.
Implement the scpi-dmm driver in such a generic way that it could work
with several protocol variants and with differing models which happen to
use any of these protocol variants. Prepare a list of supported models
with their respective SCPI command set, set of DMM functions and their
precision.
Add support for Agilent 34405A. The ten functions of this device got
tested and are operational, in continuous mode as well as with sample
count or capture time limits. The driver can query the current meter's
function, can change the function, and can run acquisitions in either
the current mode or with a user specified function selection. There is
some potential for improvement: AUTO/MIN/MAX/HOLD indicators are not
supported by this implementation.
Gerhard Sittig
Petteri Aimonen
Timo Kokkonen
Adrian Godwin