sampling

Usage

>> sampling [ mode | period | availablefastperiods | userperiodlimit | burstinterval | burstlength | gate ]

Security

Description

• mode [= <mode>] reports or sets the sampling mode for the current schedule:
  

  1. continuous mode is supported by all loggers; measurements are taken and stored at the specified period between the start and end times.

  2. burst mode is available for loggers which are so configured in the factory; measurements are taken and stored in bursts between the start and end times. The time between the start of two consecutive bursts is given by the burstinterval, the number of measurements in the burst is given by the burstlength, and the time between measurements within the burst is given by the period.

  3. wave mode is available for loggers which are so configured in the factory, and with one exception is identical to burst mode as far as the logger's behaviour is concerned. The two modes are distinct to allow host software to process the burst measurements for wave applications. The exception is that the altitude command is available only when the logger is capable of the wave sampling mode.

  4. average mode is available for loggers which are so configured in the factory. It works identically to burst mode, except that instead of storing every measurement in the burst, the average value of all measurements is computed and stored as a single sample value at the end of the burst.

  5. tide mode is available for loggers which are so configured in the factory, and is identical to average mode as far as the logger's behaviour is concerned. The two modes are distinct to allow host software to process the data for tide monitoring applications.

  6. regimes mode is available for all loggers, but is intended for vehicle integration. Instead of a deployment containing a single sampling period, averaging burstlength, etc, the regimes mode permits multiple sampling periods, averaging bins, and sampling periods to be set for different environmental conditions-pressure regimes.

  7. ddsampling mode is available for all loggers, but is mainly intended for vehicle integration. Instead of a deployment containing a single sampling period, the ddsampling mode permits two sampling periods depending on the the current direction of the logger (descending or ascending). See command ddsampling.
     

     Use of directional dependent sampling requires the logger to have a suitable sensor for measuring pressure.  Firmware versions 1.135 or later will check this condition when an attempt is made to set ddsampling mode.  If no suitable sensor is available the following error message is returned:
     

     Error E0114
     
     

     For reasons relating to the logger's internal operation, not all types of pressure sensor are suitable for use; for example, high precision quartz sensors can not be used to control directional dependent sampling.

     
     
     

• period [= <period>] reports or sets the time between measurements.
  This is straight forward in continuous mode; in any of the other modes it is the time between continuous measurements within the burst. The <period> is specified in milliseconds.
  Values for 1Hz sampling or slower are supported by all loggers, and must be given in multiples of 1000. In continuous mode the permitted range is typically 1000 (one second) to 86400000 (24 hours), in increments of 1000. Some loggers may have a lower limit which is more than 1000 if an attached sensor has a very slow data acquisition time. For all other modes the upper limit is 255000 (about 4 minutes); this is unlikely to be a constraint in practice, as the period is the time between measurements within the burst.
  If the logger is configured to support fast (sub-second) measurement periods for the selected mode, the <period> must correspond to an exact frequency in Hz, to the nearest millisecond. Permitted values are further constrained to a supported subset of sample rates, which may be determined via the availablefastperiods parameter described below. See also Tips for system integrators.
  
  Note that fast measurement periods may be supported in some modes but not others, depending on the logger's configuration.
  
  

• availablefastperiods reports a list of the fast measurement periods available for the logger for sampling rates faster than 1Hz. Each available period is reported to the nearest millisecond, and the values are separated by a vertical bar, or 'pipe' character, '|'. If there are no fast periods available, the word none is returned instead of a list of values. When a list is reported, the period for sampling rates faster than 1Hz can be set to any value in the list, but no others.
  
  Note that the periods given in the list may be supported in some modes but not others, depending on the logger's configuration.
  
  

• userperiodlimit reports the minimum period which can be used in 'fast' sampling modes, in milliseconds; the period can not be set to a value less than this.
  
  
• gate reports any gating condition currently enabled.
  A gate is an extra requirement that must be satisfied before sampling will occur, in addition to the logger's current time being between the start and the end times. The following gating conditions are presently defined:
  1. none: no gating conditions are enabled.
  2. thresholding: a threshold requirement must be satisfied; see the thresholding command.
  3. twistactivation: the end-cap must be in the "on" position; see the twistactivation command.
  4. invalid: two or more gating conditions have been selected, this is not currently possible and will prevent the logger from being enabled.

For further information about gated sampling, see the section Gated Sampling.

• burstinterval [= <burstinterval>] reports or sets the time between the first measurement of two consecutive bursts; it is not the gap between the end of one burst and the start of the next. The <burstinterval> is specified in milliseconds.
  The absolute limits of the permitted range are 1000 (one second) to 86400000 (24 hours), and the <burstinterval> must be set to a multiple of 1000. However, before the logger can be enabled for sampling the value set must also be consistent with the measurement period and burstlength.
  
  

• burstlength [= <burstlength>] reports or sets the number of measurements taken in each burst.
  The permitted range is 2 to 65535, but before the logger can be enabled for sampling the value set must also be consistent with the measurement period and burstinterval.
  The constraining relationship between the burst parameters is: burstinterval > (burstlength * period).

Examples

The logger has been programmed for continuous 8Hz sampling. It supports 2Hz, 4Hz, 8Hz, and 16Hz operation. The programmed values of the burst parameters are reported but do not apply to continuous sampling. No gating condition is in force.

  Averaging enabled without changing the other parameters; the logger is now programmed to take a burst of 60 measurements at 8Hz every five minutes, and store the average of the 60 measurements.

  The mode is changed to burst recording and the burst interval to ten minutes; the logger is now programmed to take a burst of 60 measurements at 8Hz every ten minutes, storing all measurements in memory.

The logger has been programmed for continuous 4Hz sampling. This logger does not support any of the other modes, so the parameters are not reported.

The first example shows support for sampling at 2Hz, 4Hz, 8Hz and 16Hz in at least one of the available modes; the second example shows that no sampling faster than 1Hz is supported.