www.vtiinstruments.com
EX1629 Basic Operation
57
The confidence scanlist contains the list of confidence channels to be measured on each main
input channel. There is a single confidence scanlist for the entire instrument, so all channels in the
main input channel scanlist have the same confidence measurements taken. That is, if there are 16
channels enabled in the main input scanlist, say channels 0 through 15, and the confidence scanlist
is configured with 4 channels, say excitation current (positive and negative) and excitation output
voltage (positive and negative), 64 confidence measurements will be taken (16 x 4).
The confidence system runs at a fixed rate (500 Sa/s), regardless of the sampling rate of the main
input channels, and asynchronously to the main input measurements. Confidence measurement
data is inserted into the same data stream as the main input channel data. When the main input
sampling rate is equal to or less than 500 Sa/s, all scans of data include confidence data. Between
500 Sa/s and 1000 Sa/s, confidence data is included in the scans when available – the data stream
is self-describing a manner such that clients can tell when confidence data is available and when it
is not. Above 1000 Sa/s, the confidence data is not available.
NOTE
The key restriction that MUST be enforced is that any confidence scan list that includes
+V_SENSE and -V_SENSE must also iEXCITEOUT and -EXCITELOW as well.
C
ONFIGURATION
S
TORAGE
By default, all configuration options on the EX1629 are at factory defaults when the instrument is
powered-on or is reset. The instrument does support the ability to save user configurations to non-
volatile storage, however. This option saves all configuration variables, and automatically restores
them at power-on or reset, instead of using the factory defaults.
To aid developers, the instrument can generate a “digest” (also known as a “hash”) for the
instrument’s configuration. This digest is a statistically unique value, 16 bytes long, that serves as
a signature or fingerprint for the current configuration state of the instrument. By configuring the
instrument with the desired values and then saving the configuration to non-volatile storage, the
configuration will be available whenever the instrument powers on or is reset. Additionally, by
retaining the digest of the configuration when it is stored, an application can quickly verify that the
instrument is configured identically to the desired state, without laboriously retrieving all
configuration variables and verifying them against the desired state.
NOTES
1)
The configuration storage (and digest) pertains only to the acquisition configuration of the
instrument (e.g., scanlist, EU conversions, excitation voltages, etc.). Other instrument
configuration, such as network and time configuration are not covered by this mechanism.
2)
Due to the way in which the internal configuration state of the instrument is stored, digest
values for the factory default configuration as well as digest values for saved configurations
may change between firmware versions.
W
IDEBAND
O
UTPUT
The wideband output connector carries a buffered image of the main channel signal. It is a single
ended signal, referenced to GND, and shielded to the chassis. The magnitude of this signal is
±15 V. Assmann Electronics’ P/N: AHDS44LL-Z is one example of a mating connector.
15
30
44
1
16
31
F
IGURE
3-9:
W
IDEBAND
O
UTPUT
C
ONNECTOR
Содержание EX1629
Страница 310: ...VTI Instruments Corp 310 EX1629 Command Set...
Страница 342: ...VTI Instruments Corp 342 EX1629 Onboard Memory...