Caveat: Effect of
In every case, the use of
$ref is to totally substitute that line by the content referenced in the file path (under the “#” tag). It is completely equivalent to write the content of referenced file instead of the
$ref line. This should be taken into account for syntax purposes. If syntax is not validated, a very good chance is that the
$ref file syntax is either wrong or in the wrong place. Not finding the file also causes problems which are not evident at first glance; if you keep getting errors, check if the file is in the right place.
Caveat: Cryptic syntax messages
Unfortunately, the JSON/YAML parser is very terse reporting syntax errors such as unmatched parentheses, brackets or curly brackets, single items instead of lists, etc., usually result in an exception with a cryptic message. It is strongly recommended that YAML files are edited in a suitable editor which can check at least basic syntax errors. See also the Troubleshooting section below.
Caveat: Use of response stages
Although response stages are specified at the component (sensor, preamplifier and datalogger) level, in the end they are considered as a single response for the whole instrument. Response stages are taken in this order: sensor stages, preamplifier stages and datalogger stages, irrespective of the order in which components appear in the information file. Within a component, they are taken in the order specified in the information file. In the end, they are numbered from one to n for the whole response.
Caveat: Treatment of sample rates in response stages
Only the input sample rate should be specified for a response, starting in the ADConversion stage. All other input and output rate are calculated using the decimation factor of each digital stage. Therefore,
output_sample_rate should never be specified for later digital stages, and decimation factor should always be specified for them.
Total sample rate is calculated for the whole response and checked against the sample rate specified in the datalogger. A warning will be issued if they are different.
Caveat: ALWAYS follow the syntax and beware of $ref overwriting your attributes
A naïve approach to syntax might think that we can add fields, for example, to a $ref information file. For example, the file could be an instrumentation file and we could decide to add a datalogger configuration which is not present in the file:
“$ref” : “instrumentations/BBOBS1_2012+.instrumentation.yaml” datalogger_config: “62.5sps”
This is wrong. First, it is the wrong syntax: what channel with the configuration be applied to? There is no indication of that. Remember: modifications should always follow the same syntax. If
datalogger_config belongs under a channel, it should always be applied to a channel.
But there is another problem. “$ref” will substitute all attributes at the same level, thus erasing the attribute
datalogger_config. If this happens it will be a silent error, since substitution occurs before validation and the application will never know
datalogger_config was there. The correct way of applying
datalogger_config is through
channel_modifications at the station level.