VTI Instruments EX1401, User Manual

Page: 88 / 114

VTI Instruments Corp.
88 EX1401 Instrument Drivers
0x00000020 Open Transducer
The OTD trickle current is enabled and has caused
the input voltage to rise above the upper limit of the
ADC’s valid input range.
0x00010000 ADC Overload
The signal is outside of the ADC’s valid input range,
either too high or too low.
0x00100000 ADC Sync
The channel’s ADC has become unsynchronized
from the others in the instrument, likely due to
electrostatic discharge. While this status bit remains
set, the firmware is resynchronizing it.
T
ABLE
5-2: I
NSTRUMENT
-S
PECIFIC
F
AULT
S
TATUS
B
IT
S
UPPORT
T
IME
S
TAMPS
During data acquisition, the EX1401 returns timestamps along with digitized analog data. The
timestamps are created based on the
TimestampSource clock specified in the ReferenceOscillator
interface. When IEEE 1588 synchronized time stamps are desired, the TimestampSource property
must be set to ReferenceOscillatorTimestampSourceSystem . Otherwise, the time returned will be
the time elapsed since the SYNC signal was received.
When measurement data is retrieved, both a timestamp of the data record and a timestamp of trigger
event are returned. The combination of
TimeSeconds and TimeFraction parameters indicate the time
of the first data sample in each retrieved data record. The time of trigger event is returned in the
AdditionalData parameter.
Timestamp Source Timestamp value Resolution
System (IEEE 1588) PTP or TAI (International Atomic Time) 40 ns
PXIe_CLK100 Elapsed time from last SYNC 40 ns
T
ABLE
5-3: T
IMESTAMP
S
OURCE AND
R
ESOLUTION
A
DDITIONAL
D
ATA
The additional information associated with the data records are returned as a JSON (Java Script
Object Notation) array of name/value pairs:
[[JSON array for channel 1’s first record], [JSON array f or channel
2’s first record], … ]
The JSON object array for each channel is:
[{Object1}, {Object2}, …]
Each object is a list of name/value pairs:
{name1:value1, name2: value2, …}
JSON objects can be parsed using the following defined name strings.