Why do Real-time Dashboards sometimes show "no data"?

ArchFX Real-time Dashboards are built using the Grafana open-source business intelligence tool and are made up of queries to a time-series database and/or a relational database. Sometimes a query will return a null result. When Grafana gets a null result for a query, it will show "no data." This typically doesn't mean that the dashboard has a bug or that data is missing from the database.

For example, the Lines with Same PnP as Takt Time and Cycle Time Bottleneck dashboard will check and see if any P&Ps at a site both has the longest takt time (time between product ready events) and cycle time (program running time) on their lines. If so, the query will list all P&Ps that match that query. If there is no P&P at the site that has the longest takt time (time between product ready events) and cycle time (program running time) on its line, the Lines with Same PnP as Takt Time and Cycle Time Bottleneck dashboard will simply show "No data."