Yes. Lay the fixed page out in a word processor, export it at the panel's exact pixel size, and import it as one image. Size body capitals to at least viewing distance divided by 150, which on a 15-inch 1024 × 768 panel read from 3 ft means a font near 30 px.
A screen full of instructions does not have to be built from dozens of text objects. Lay the page out once in a word processor, export it at the panel's exact pixel size, and import it as one picture. The picture carries headings, spacing and layout with it, and the project holds a single object per page. Text size decides whether it works: words exported as pixels keep the size they were exported at. Set the letter height for the viewing distance before export. Here is the rule, the steps, and the arithmetic for a 15-inch panel read at arm's length.
How big the text has to be
Size body-text capitals to at least the viewing distance divided by 150, in matching units. One unit of height per 150 units of distance makes each capital subtend about 23 arc minutes. That is a step above the 20 to 22 arc minutes that ergonomics guidance puts forward as the minimum for characters read as a task. Where the readout lives with glare, vibration or a tired crew, tighten the rule to distance divided by 100, about 34 arc minutes, and the letters grow half again.
Road-sign tables are looser by design: the 30 ft of viewing distance per inch of letter height figure (FHWA) works out to about 10 arc minutes, enough for short, bold, guessable words. Work instructions are read line by line at a machine, so hold them to the 23 arc minute rule above.
The rule turns into pixels through the panel's pixel pitch, which comes from the pixel dimensions, not the inch size. That pixel-count view is the same one behind why two HMI panel sizes share one layout in pixels. For room-scale signage the full method sits in what size digital signage screen do you need.
What you need
- The panel's pixel dimensions, from the screen setup in your HMI editor or the panel manual.
- The real viewing distance, measured where the operator stands.
- A word processor or drawing tool that can set a page at a fixed pixel size, or a print-to-image and screenshot path that ends at fixed pixels.
- The image format your editor accepts. Most take PNG or JPG; the file-type list in the import dialog settles it for yours.
- A copy of the project, so the first page is checked in the copy before it goes into production.
How to build and import the page
- Read the screen size in pixels from the editor's screen properties, for example 1024 × 768 on a 15-inch 4:3 panel.
- Measure the eye-to-screen distance where the operator actually stands. At a machine it is usually 2 to 3 ft.
- Compute the minimum capital height: distance divided by 150, in millimeters. Convert to pixels by dividing by the pixel pitch, which is 25.4 mm divided by the panel's pixels per inch.
- Set the page size in the word processor to the panel's exact pixels. Pick a font that clears the minimum: capitals run about 0.7 of the font size in most text fonts, so divide the pixel target by 0.7 and round up.
- Lay the page out as one column of about 60 characters, line spacing 1.4 to 1.5, and margins you can repeat on every page.
- Export at exactly the panel's pixels. The dpi value inside an image file is a print hint; the panel shows pixel counts, so a 300 dpi export buys nothing over the same pixels at 96 dpi. The confusion between dpi tags and physical size is the whole subject of calibrating pixels to mm from an image dpi value.
- Import the picture through the editor's image or picture object and place it at 1:1, so the panel does no scaling.
- Download the project to the panel and run the checks under How to check it worked below.
Worked example: a 15-inch panel read from 3 ft
Take a 15-inch 4:3 panel with a 1024 × 768 screen, read from 3 ft at a machine.
Pixel pitch: a 15-inch 4:3 panel has a 12 by 9 inch active area. 1024 pixels across 12 inches is 85.3 pixels per inch, and 25.4 ÷ 85.3 gives 0.30 mm per pixel.
Minimum capitals: 3 ft is 914 mm, and 914 ÷ 150 = 6.1 mm. In pixels, 6.1 ÷ 0.30 = 20.4, so capitals need 21 px. A font at 30 px has capitals around 21 px and clears it; the same font at 28 px lands near 20 px and falls just short.
Page budget: hold 44 px margins top and bottom, leaving 768 - 88 = 680 px. Line spacing 1.5 on a 30 px font gives 45 px per line, and 680 ÷ 45 = 15.1, so the screen carries 15 lines. Across the width, 1024 - 120 px of side margins leaves 904 px, and proportional fonts average about half the font size per character, so 904 ÷ 15 = 60 characters per line.
One screen therefore holds about 15 lines by 60 characters, some 900 characters of instruction text, a heading plus a solid page of steps. Move the same panel to a 2 ft reading position and the numbers shift: 610 mm ÷ 150 = 4.1 mm, 4.1 ÷ 0.30 = 13.7 px, so a 20 px font now clears it, line spacing drops to 30 px, and 680 ÷ 30 = 22.7, about 22 lines per screen.
When text objects still win
- Any line that changes at runtime stays a text object bound to its tag or register. You can sit that object on top of the image, aligned to the baked-in layout, and keep the fixed frame as pixels.
- Pages you edit often are cheaper as text objects. Every image fix is four steps: edit the document, export, import, download. Across dozens of pages that becomes the maintenance plan.
- Keep the editable source file for every image page beside the project, named and revision-marked. Without it, the next correction starts from a flattened picture.
For procedure pages meant to be read step by step at the machine, the layout choices here are the same ones in putting maintenance procedures on an HMI panel as readable pages. If the pages are reference material for people at a bench, with no machine project behind them, a separate screen that plays exported images from a card does the job with no HMI editor at all; our display category is that range.
How to check it worked
- Open the screen on the panel, in the copy first, and have someone who has not seen the page read it cold at the measured distance.
- Look at character edges. Soft edges mean the panel scaled the image, so put the object back to 1:1 or re-export at the panel's pixels.
- Check for clipped text at the edges and walk the navigation: one screen per page, reached the way operators will reach it.
- Compare the displayed page against the approved procedure and record its revision on screen. If a page carries a safety-critical step, the controlled document is the master copy; a correction flows from that document into a fresh export and reaches the panel by download, and it is never typed straight onto the screen.
Recommendation: For fixed instruction pages read at arm's length, export each page at the panel's exact pixel size, set capitals to distance divided by 150, import the page as one image and place it 1:1. Keep any line that changes at runtime as a text object on top of the image, and keep any page you expect to edit more than a few times in the panel's life as text objects instead. Archive the source document for every image page next to the project so a revision is a fresh export, never a rebuild.
Questions
Can the panel load instruction pages straight from a USB stick at runtime?
Importing an image into the project and reading fresh pages from removable storage at runtime are two different workflows. An imported image is part of the project file, so it downloads with the project and shows with nothing plugged in. Displaying files from a stick needs a file, recipe or media object that your panel's documentation lists for exactly that job. If the manual documents none, build the pages into the project as imported images and update them by download.
Does an imported page survive a power cut?
Yes. The picture is stored in the panel as part of the project, the same as every other screen object, and the screen redraws from that stored copy at power-up. No PC, network or stick is needed. This is the practical advantage over keeping pages outside the project: a replacement panel shows the same pages as soon as its project is downloaded, with nothing else to copy.
What if the editor places my image at the wrong size?
Set the object's width and height to the picture's own pixel count, or 100 percent, before you save. The editor shows object size in screen pixels next to the placement handles. A stretched object makes the panel resample the image and small text goes soft. Re-import the file instead of resizing, and check one page against the source document before you batch the rest of the set.
How do I keep image pages maintainable over years?
Keep the editable source file for every page beside the project files, with the page name and revision in the file name. When a procedure changes, edit the source, export at the panel's pixel size, import over the old picture and download. Give the export the same file name each time so the project history stays traceable, and record the revision shown on screen so operators can spot an out-of-date page.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.