Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 509)

Appendix B. Campbell Scientific File Formats
B.1.8.2 File Syntax
CSIJSON contains two subordinate objects: “head” and “data”. The head
object contains the station meta-data and field descriptions while the data
object is an array of record objects.
B.1.8.2.1 The head Object
The head object contains information about the datalogger and program that is
responsible for generating the data as well as information about the fields in the
data.
B.1.8.2.1.1 head.signature
This numeric value is the signature calculated on the table definitions. This
value can be used by the web client to determine whether the table definitions
have changed while that client is monitoring or polling for data. If the web
client is using the DataQuery command in the datalogger web services and
specifies a tablesig value that matches this value, the server will not send the
head.environment or head.fields values.
B.1.8.2.1.2 head.transaction
This optional value specifies a transaction identifier that can be sent by a web
client in the DataQuery parameter. This value can help the client route
responses to the correct object.
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