Device field value change (number) shows recorded changes to numeric fields on device cards over time. You can view one Spot or compare several Spots and fields. Each combination of a field and a Spot forms its own series.
The report name does not mean that differences between readings are calculated: the chart shows newly recorded values or their averages. The data does not come from Spot messages, changes to the field description or the current value alone. The separate history of the operating hours meter also belongs to a different report.
Prerequisites
You need permission to view the Spots you want to examine. The Attribute selection offers numeric fields that are in use and visible with your permissions. The field must have recorded value history for the period you are examining; an unchanged current value alone does not produce a reading on the chart.
An administrator adds the report to the page and saves its settings. Other users can change the filters on the visible report for viewing purposes. Changing a field value separately requires permission to edit the Spot. See Editing Spot details.
Choose fields with the same unit of measurement for comparison. The report does not convert, for example, temperature, pressure and operating hours into comparable quantities.
Open the report and select the data
- In the browser menu, open Dashboard → Report pages and select a report page. If the report is missing, an administrator selects Add new report on the page, finds the Device field value change (number) report and drags it onto the page.
- Open Settings in the report’s title bar. In the panel that opens, select at least one Attribute and one Spot in the All filters section. No data is retrieved without these selections.
- Above the chart, select Tme period for the data. Date range is suitable for checking a specific period; set the dates under Time period specification. The default is Rolling data.
- In the same area, select Time grouping for data: minute, hour, day, week or month. The default is hour. The time period determines which changes are retrieved, while time grouping determines the intervals used in calculations.
- In the settings panel, under Report settings → Chart type, select Bar, Line or Spline. The default is Line. Check the legend on the updated chart to make sure the series match the fields and Spots you want.
Field value changes successfully saved to the server from Android and iOS can be included in the same report data. These instructions cover viewing the report in the browser interface.
How is the reading calculated?
Enable time aggregation in the All filters section calculates the arithmetic mean of the new values in each interval for each combination of a field and a Spot: the sum of the values is divided by the number of value changes within the interval. Each change has equal weight, regardless of how long the value was in effect.
If a value is changed first to 10 and then to 20 within the same hour, the result for that hour is (10 + 20) / 2 = 15. The result is neither a change of 10 nor a sum of 30. The calculated value is rounded to four decimal places; the chart may not display trailing zeros.
Aggregation is enabled by default. It can only be disabled when grouping by minute; at other levels, it is enforced. Without aggregation, the last new value in the display interval is used and is also rounded to four decimal places. Multiple changes within the same interval are not shown as separate points. With dense data, display intervals may also be longer than a minute.
If there is no value change in an interval, the previous reading is not carried forward into it. Leading and trailing intervals in which none of the series has a value are removed from the aggregated display. The points on the chart therefore do not represent the field’s value continuously over time.
Empty intervals, zeros and the other average setting
In aggregated Line and Spline displays, zero points are added at the edges of empty intervals for drawing purposes. Such a zero is not a recorded measurement. Clearing a field can also produce a zero in the calculation, because the new value in the history is converted to a number. Check the field history to determine where the zero came from.
Fill empty data points in the Report settings section affects the display of zero points and their associated lines in the line chart. When the option is off, actual zero readings may also be hidden. Do not infer that a measurement is missing solely from a break in the line. The gap-edge zeros described above are not added to the Bar display.
Show average in the same section is separate from time grouping. It adds the average of the series displayed at each X-axis position. Missing series values are treated as zeros and included in the divisor; zeros added to the display can also affect the result. The result is rounded to two decimal places. For example, a series value of 20 and a missing value in another series produce an average of 10. This option is off by default.
Keep Show average off when checking the value history of an individual field. When you change these display settings, reload the report data, for example by reopening the page: turning off the average alone does not restore empty points that have already been converted to zeros.
Data limits and known issues
The report includes a maximum of 20 Spots. Selected Spots are given preference when determining which Spots to include, but selecting more than 20 Spots does not guarantee that all of them will appear. Split large comparisons into smaller groups. The report uses Spots and their fields that still exist; old history from a deleted field alone does not guarantee that its series will appear.
History retrieval shortens an excessively long date range based on the end date:
- Minute: the earliest start is the beginning of the end date.
- Hour: the earliest start is the beginning of the day seven days before the end date.
- Day: the corresponding limit is 365 days.
- Week and month: the corresponding limit is 1,825 days.
The user’s time zone affects how timestamps and calculation intervals are handled; the default is Helsinki. Check the time period used, especially for changes near the boundary of a day or week.
There is an issue with minute-level rolling time: the automatic day boundary can place the start date after the end date. To check minute-level data, use Date range and specify a single day.
There is an issue with the calculation boundary in weekly grouping: the last included day of the week ends at the beginning of that day in the calculation, so changes later that day may be excluded from the weekly reading. Check such data using daily grouping and the field history. Do not use the weekly reading to confirm a complete week.
Save and verify the result
After adding a new report, an administrator selects Save the page. For a report that has already been saved, Save Settings appears in its title bar and saves its filters and display settings. Reopen the page and check that the selections were retained. Saving changes the report settings; it does not change, restore or delete the Spot’s field values or their history.
First verify the calculation using one known Spot and field. In the browser, open Assets, devices, tools, open the Spot by clicking its name and find the field on its form. Open the history icon next to the field, select the same time period and use the Only fetch value changes filter. Compare the timestamps and new values of the changes with the report’s intervals. See the detailed instructions for checking a field’s value history.
If an expected series or reading is missing, check the required selections, permissions, changes in the history, the date range retrieval limit and the limit of 20 Spots. Start with one Spot and use the Bar display with Show average off. For general troubleshooting, see Troubleshooting an empty report or a report that will not load.