Ptp Triggered Scan; Zero Offset Calibrations; Differential Modules - Scanivalve DSA5000 Series Operation And Service Manual

Section 3: Operation

PTP Triggered Scan

The IEEE1588 protocol allows DSA5000 units to start scan-
ning at a preset time and date while keeping their data
samples time synchronized. This allows a user to syn-
chronize the scan start time across multiple units. A scan
start time and date in the future can be configured in the
DSA5000 using the Scan Start Date (SSD) and Scan Start
Time (SST) variables. After a SCAN command is issued, the
DSA will enter scan mode but will not output data. Once
the SST and SSD time has been met (based on the inter-
nal time of the DSA), the time will trigger the DSA to start
releasing frames of data at the set internal rate. If SST and
SSD are set for a time in the past (based on the internal
time of the DSA), a SCAN command will execute a scan and
the DSA will release data immediately.
The following table describes a start scan time with two
DSA5000 units when setting SSD and SST for a time in the
future.
Two (2) DSA5000s configured with:
SST = 12:00:00, SSD = 2021/2/10, RATE = 1Hz
SCAN
11:59:55 2021/2/10
to DSA 1
11:59:56 2021/2/10
SCAN
11:59:57 2021/2/10
to DSA 2
11:59:58 2021/2/10
11:59:59 2021/2/10
12:00:00 2021/2/10
12:00:01 2021/2/10
12:00:02 2021/2/10
12:00:03 2021/2/10
Note: Due to high scan rate ability and the high-accuracy of
PTP time stamps, it is possible to have a scan start variance
of up to 125us when using SST/SSD to start data sampling.
While the scan may not start exactly on the time requested,
the PTP timestamps in the frame of data will reflect the
exact time the data was sampled.
The following table describes a start scan time with two
DSA5000 units when SSD and SST are a time in the past.
1 1 1612987201 1612987201
2 2 1612987202 1612987202
3 3 1612987203 1612987203
Two (2) DSA5000s configured with:
SST = 12:00:00, SSD = 2021/2/10, RATE = 1Hz
12:59:55 2021/2/10
to DSA 1
12:59:56 2021/2/10
12:59:57 2021/2/10
to DSA 2
12:59:58 2021/2/10
12:59:59 2021/2/10
1:00:00 2021/2/10

Zero Offset Calibrations

The DSA's internal calibration valve incorporates a zero
offset correction feature (Quick Zero). This feature provides
a simple and quick means to correct for the minor zero
drift problems inherent to piezoresistive sensors. Even
with pressure applied to the Px ports, the calibration valve
can be configured into Calibrate mode, providing a pres-
sure to be exposed to the positive and negative side of all
transducers. At that point, with the sensor at its natural
zero state, any offset can be read and recorded. This can
then be factored into the engineering unit conversion and
mathematically removed. Quick Zero calibrations can be
performed in under 10 seconds.
Due to the nature of the piezoresistive sensors used in
the DSA modules, it is recommended that a quick zero
calibration be performed at least daily. Performing a quick
zero more often will not cause any problems and is highly
encouraged. There are no issues using the quick zero cali-
bration each time before data is collected. Keep in mind, if
the temperature of the module changes more than 5°C, a
fresh quick zero should be performed.
Zero offset corrections may become obsolete after several
hours or after the module has changed temperatures.
While the deltas can be saved through a power cycle,
changes in the environment may cause the deltas to be
obsolete.

Differential Modules

For differential modules, a quick zero offset calibration can
be executed using the simple command: CALZ.
In order for the calibration valve to successfully switch and
place the module into Calibrate mode, 90-120 psi clean, dry
instrument grade control pressure air must be supplied to
the CTL SUPPLY port. In the modules default configuration,
18
18
SCAN
1 1612990796
SCAN
2 1612990797
3 1 1612990798
4 2 1612990799
5 3 1612990800
DSA5000
1612990798
1612990799
1612990800