Combo Chart+

Overview

When to use it

Use this symbol when you need to:

• Trend values together as lines, areas or bars, each on its own value scale when their units differ.
• Show equipment states such as running, stopped or failure next to a measurement.
• Investigate a period: zoom in, place two rulers and read the average, minimum and maximum between them.
• Color a value by limits and draw the limit lines.
• Relate process changes to event frames.

Choose Asset Time Series Chart+ to plot the same attributes for every asset found by an asset search. Choose Period Comparison Chart+ to compare one value in different periods, and Control Chart+ to judge statistical control.

Before you begin

• Use PI Points or AF attributes. Line, area, bar and scatter traces need numeric values. Digital, enumeration and Boolean sources show states, and string sources show text markers.
• Configure PI Web API for Vision Library+. The chart loads its own history, and the summary table and event frames use the same connection.
• Values that share a value scale or a range area should have the same unit. An AF attribute can be shown in another unit of the same kind with Display unit.
• To create event frames you need an AF database, an event frame template and write permission.

Add and set up the symbol

1. Select Combo Chart+ in the PI Vision symbol gallery.
2. Drag the first data source onto the display, for example a tank level. Drag a second one onto the chart, for example a feed rate.
3. Right-click the chart and select Configure Combo Chart....
4. Under Data Retrieval, set Mode to Interpolated and Interval to 20 Minute. This gives one value per interval, which keeps a fast signal readable.
5. Under Trace Options, select each data source in the list and enter a Label.
6. Close the pane. The chart shows one trace per data source, each on its own value scale, and the legend shows the latest values.

A new chart starts with Mode on Default, which suits slow signals.

Common tasks

Show values as lines, areas and bars

Use this when a value reads better as a filled area or as columns, for example a quantity per interval.

1. Right-click the chart, select Configure Combo Chart... and scroll to Trace Options.
2. Select the data source in the list (1).
3. Set Type (2) to Line, Area, Bar, Scatter or Range Area. Here the tank level is an area and the feed rate is a bar.
4. Under Data Retrieval, keep Mode on Interpolated, or choose Summary and an Interval. Neighboring bars then cover equal intervals.

The tank level is drawn as a shaded area and the feed rate as columns, each on its own scale.

An unstacked area scales to its data like a line. Bars and stacked areas keep zero on their scale. To start an area at zero, set Scale Range to Custom with Minimum 0. Set Type to Range Area on one data source and choose the second under Target to shade between two values, such as an upper and a lower boundary.

Give values with different units their own value scale

Use this when one scale would flatten a value or mix units, such as a level in percent and a flow in kilograms per second.

1. Under Scales > Value Scales, set Scale Type to Multiple (1). Each data source then gets its own scale in the color of its trace.
2. Under Trace Options, select a data source and expand Axis Y.
3. Set Position (1) to RIGHT to move the scale to the other side.
4. Set Scale Range (2) to CUSTOM and enter Minimum and Maximum (3), for example 0 and 60.

The tank level uses the left scale from 0 to 100 percent and the feed rate uses the right scale from 0 to 60 kg/s.

Use Single for values with the same unit. Separate draws one plot per data source on a shared time axis. Custom lets you add named scales with + Add Scale and assign several related data sources to each one with the Axis Y list of a trace. A Single or Custom scale also offers Stacking.

Show equipment states next to a measurement

Use this to see which state the equipment was in while a value changed. The data source must be digital, enumeration or Boolean, such as a motor status.

1. Drag the state data source onto the chart.
2. Under Trace Options, select it (1).
3. Set State display (2) to TREND or BANDS.
4. For TREND, set Scale Type to Multiple or Separate under Scales > Value Scales, so the states get their own scale with state names.

TREND draws the state as a stepped line against named ticks. On a Single scale it plots the numeric state codes instead.

BANDS shades each state over the plot, with a label at its start and a legend entry per state.

State colors and names come from the data source's states. With Enable Multi-State on, you can change the colors under States; see Mark limits and color a value by range.

Zoom and pan into a period

Use this to look at part of a long range, for example the hour a motor ran.

1. Hover the chart to show the toolbar. A new chart has Show Toolbar on under Trend Options > Toolbar.
2. Select Box zoom (2) and drag across the period.
3. Or select Zoom In (3) to halve the visible time, and Zoom Out (4) to double it.
4. Select Pan (1) and drag the plot to move the window.
5. Select Reset Zoom (5) to return.

The chart shows the dragged period, here 9:30 AM to 11:30 AM.

With Apply to Display Time on, which a new chart has, the zoom also sets the display time range, so every symbol that follows the display shows the same period. Reset Zoom restores the range the display had before. Turn Apply to Display Time off under Interactivity to zoom only this chart. The mouse wheel zooms too.

Read statistics for an interval

Use this to compare the average, minimum and maximum of each trace over a period you choose.

1. Under Summary Table, turn Show on (1) and Start Expanded on (2).
2. Turn on the columns you need, for example Standard deviation (3).
3. Click the plot to place ruler A and click again for ruler B. Rulers are on for a new chart under Interactivity > Synchronize > Ruler.

The table adds the columns A, B and B - A and shows the average, minimum and maximum between the rulers. Without rulers it covers the display time range.

In this example the motor ran at an average of about 641 rpm between the rulers. The table uses server values for the interval, so they can differ from the boxes at the rulers, which use the points the chart has loaded.

Mark limits and color a value by range

Use this to see at a glance when a value is low, normal or high.

1. Right-click the chart and select Add Multi-State....
2. Select the data source in the list and check Enable Multi-State (1).
3. Under Options, turn Color series (2), Lines (3) and Bands (4) on.
4. Under States, set the upper limit of each range (5) and choose its color. Values below the lowest limit are bad data.

The trace changes color with the range it is in. Dashed lines mark the limits and shaded bands mark the ranges. Here the level is amber below 35 percent, green up to 60 percent and red above.

Use the symbol

Interactions

• Hover the plot to read every value at the pointer time. Lines and areas interpolate between points, steps and bars hold the previous value, and a scatter trace needs a point at that time. A gap in the data stays a gap.
• Click the plot to place ruler A, then ruler B. Drag a ruler's handle to move it, or select Clear rulers. With both rulers placed, the plot outside them is shaded, and an A-B arrow at the plot edge points to rulers outside the visible range. Hover and rulers are shared with other time-series charts on the display.
• Zoom with the mouse wheel or the toolbar. With Apply to Display Time on, drag the plot past its start or end in Pan mode and the display time range follows. The newly exposed part loads when you release.
• Click an event frame label to open its details. What you can do there depends on your permissions.
• Select Fullscreen to open the chart in a larger dialog, and Download to save it as PNG, SVG, PDF, CSV, JSON or XLSX. The data files hold the loaded samples with timestamp, value, unit and status. Fullscreen and downloads leave out the summary table.

Nothing in the chart writes data, except Save in the event frame form, which creates an event frame in AF. While creation is on, dragging draws the creation band and the zoom buttons are not available.

Configure the symbol

The pane has the sections Trend Options, Scales, Data Retrieval, Time Bar, Interactivity, Summary Table, Trace Options, Data Quality, Events and Export Data. Multi-state settings open from the context menu.

Trend Options

Scales

State scales show every defined state at an evenly spaced tick and hide range, logarithmic and tick controls.

Data Retrieval and Time Bar

Interactivity

Summary Table

The statistics are server values, weighted by time. The table range is the interval between the rulers, otherwise a Select interval, otherwise the symbol time range. See Read statistics for an interval.

Trace Options

Select a data source in the list. The arrow buttons reorder it and the delete button removes it from the chart.

A string source shows time markers with text labels.

Multi-state

Data Quality, Events and Export Data

Troubleshooting and limitations

See Troubleshoot chart data loading for the PI Vision log and what to send to support.

• Limitation: Fullscreen and downloads do not include the summary table.
• Limitation: Statistics and event counts are server values. Missing values are left empty; the table does not calculate them from the chart.
• Limitation: A digital trend is not drawn with Summary retrieval.
• Limitation: Moving past the loaded range is not available with Apply to Display Time off, on a DISCRETE time scale, with Fit Data, with a custom time range, or while event frame creation is on.