Channel

Description

An OBS channel is an Instrument plus an orientation. An Instrumentation complex consists of one or several channels, each one implementing the signal processing of an instrument.

Actual channels all have string labels, which are usually channel numbers. They must specify an orientation. Default chann properties can be specified with a label default. This is not an actual channel. These properties are common to all channels unless overridden by attributes present in specific channels. For example, if a sensor X appears under the label default but a sensor Y appears under the label “2” then for channel 2 the selected sensor will be Y. If a preamplifier Z is specified under the label default and no preamplifier is specified under the label “2”, then channel 2 will have preamplifier Z. All attributes can be specified under the default label.

Configurations are defined at the instrument component level, but are selected at the channel level. A configuration selection attribute specifies a configuration for each of the three instrument components in a channel: sensor, preamplifier and datalogger. They are the attributes sensor_configuration, preamplifier_configuration and datalogger_configuration, respectively.

Python class:

Channel

YAML / JSON label:

  • channels

  • default

  • Particular string labels for each channel

Channels are part of the instrumentation information file.

Corresponding StationXML structure

Channel

Object Hierarchy

Superclass

None

Subclasses

None

Relationships

Attributes

Name

Type

Required

Default

Equivalent StationXML

Remarks

instrument

Instrument

Y

None

None

Attributes of instrument in Channel in StationXML

orientation:

Orientation

Y

None

None

  • orientation_code

List of values: X,Y,Z,1,2,3,H

Y

None

None

If orientation code is 1,2,3 or H it must include as a dictionary azimuth and dip. See example.

  • azimuth

number

Y

None

Channel. Azimuth

0.0 ≤ Azimuth < 360.0 in degrees

  • dip

number

Y

None

Channel. Dip

-90.0 ≤ Dip ≤ 90.0 in degrees

location_code

string

Y

None

locationCode

See LocationBase for details of how location codes are used.

sensor_configuration

string

N

None

None

For obsinfo use only. This selects one of the configurations defined in the instrument components.

preamplifier_configuration

string

N

None

None

For obsinfo use only. This selects one of the configurations defined in the instrument components.

datalogger_configuration

string

N

None

None

For obsinfo use only. This selects one of the configurations defined in the instrument components.

Orientation codes are a FDSN standard. By convention, if the orientation code is X, Y or Z, these represent the regular coordinates in space following the right-hand rule, within five degrees of the actual directions. So X corresponds to an azimuth of 0º and a dip of 0º, Y corresponds to an azimuth of 90º and a dip of 0º, and Z corresponds to an azimuth of 0º and a dip of -90º (the positive Z direction is towards the bottom). However, if 1, 2 or 3 are specified, these represent three linearly independent directions but not necessarily coincidental with the regular coordinates, so an azimuth and a dip _must_ be specified. The same is true of the H (hydrophone) code.

JSON schema

https://www.gitlab.com/resif/obsinfo/-/tree/master/obsinfo/data/schemas/instrumentation.schema.json

https://www.gitlab.com/resif/obsinfo/-/tree/master/obsinfo/data/schemas/definitions.schema.json

Example

Channels part of instrumentation information file https://gitlab.com/resif/obsinfo/-/tree/master/obsinfo/_examples/Information_Files/instrumentation/BBOBS1_2012%2B.instrumentation.yaml

channels:
    default:
        datalogger: {$ref: "dataloggers/LC2000.datalogger.yaml#datalogger"}
        preamplifier:
            {$ref: "preamplifiers/LCHEAPO_BBOBS.preamplifier.yaml#preamplifier"}
        sensor: {$ref: "sensors/NANOMETRICS_T240_SINGLESIDED.sensor.yaml#sensor"}

        preamplifier_configuration: "0.225x"

    "1": {orientation_code: {"2": {azimuth.deg: [90, 0]}}}
    "2": {orientation_code: {"1": {azimuth.deg: [0, 0]}}}
    "3":
        orientation_code: "Z"
        preamplifier_configuration: "1x"
    "4":
        orientation_code : {"H": {azimuth.deg: [0,0], dip.deg: [90,0]}}
        preamplifier: {$ref: "preamplifiers/LCHEAPO_DPG.preamplifier.yaml#preamplifier"}
        sensor: {$ref: "sensors/SIO_DPG.sensor.yaml#sensor"}

Class Navigation

Instrumentation <==> Instrument