A standard monitor has no signal of its own, so put a client computer between the HMI panel and the screen: the computer opens the panel's browser remote view on the local network, locked so nobody can control the panel from it. Size the monitor from the reading distance at 1 inch of letter height per 20 ft, which puts a 15-inch on stations inside about 14 ft and a 19-inch inside about 18 ft.
A standard monitor has no signal of its own, so showing an HMI screen on a larger monitor is a question of where the picture comes from. On most compact HMI panels the answer is a client computer: the panel serves its screen to a browser over the local network, the computer opens that view, and the 15 to 19 inch monitor shows what the computer shows. No internet connection is involved. You lock the session so the big screen can be read but not pressed, then size the monitor from where people stand: 1 inch of capital letter height per 20 ft of viewing distance. Below, the arithmetic for 15-inch and 19-inch screens, the other ways to move the picture, and what to confirm before you buy anything.
A monitor shows only what a source feeds it
A monitor is a panel and a backlight behind a video input. It generates nothing, so the first job is to find the signal. Your HMI panel is a closed box: open the manual for the exact model and look for a documented monitor output. A few larger panel-PC class units list one, and then the whole job is a single cable. Most compact touch panels list none, and the programming and service ports are not display outputs. If the manual shows no output, do not buy a screen yet; the picture has to travel over the network instead. The reverse arrangement, a panel acting as the display for a PC, raises the same question from the other side, and using an HMI panel as a PC monitor answers that direction.
Four ways to move the picture
The choice comes down to what the panel can serve and what the station must do. Check them in this order and stop at the first one the hardware supports.
| Path | What you add | Best for | Watch for |
|---|---|---|---|
| Panel's browser remote view on a client computer | a small PC or thin client, a network drop at the station, the monitor | a 15 to 19 inch non-touch mirror people only read | confirm the manual documents remote access for your model, and turn on the view-only setting |
| Direct video output from the panel | one cable and a monitor with a matching input | panels whose manual lists a monitor output | most compact panels list none |
| PC-based HMI client at the station | a PC, the HMI or SCADA client software and its license | stations that need their own screens or local control | it is a second HMI station with its own project, not a mirror |
| Managed thin client with an industrial monitor | a compact thin client, an industrial monitor, the management server | several stations administered as one set | server infrastructure; overkill for one station |
The browser view is the low-cost answer when the panel documents it, because the panel already holds the picture and the network is already in place. The PC client costs software and setup but gives the station screens of its own. Managed thin clients earn their keep from the third or fourth station onward.
Lock the view to display only
The panel serves its screen to a browser over the local Ethernet network. No internet is involved, and the session belongs on the machine or plant network. Before the screen goes on the wall, set the panel's remote access security so the browser can look but not press; the manual for your model documents the setting that blocks control and screen changes. Then test it from the client chair. Try to press a button on the big screen: nothing should change. Have someone switch screens at the panel and confirm the copy follows, inside the update rate the manual states.
Set the computer's video output to the monitor's native resolution, commonly 1920 × 1080 at these sizes, and scale the browser view to fill the window. Stretching the panel's picture across more pixels softens edges; text you enlarge in the HMI project itself stays crisp. One Ethernet run is good for 100 m (328 ft), which covers most panel-to-station distances; for a longer run, add a switch, as in connecting a remote HMI screen 1,500 feet from the PLC.
One boundary stays as it is: the aux screen is a copy for people standing farther back, and the machine's local controls, alarms and stops remain what its design requires.
Example: 15-inch and 19-inch monitors at a 10 ft station
Inputs. The reading post stands 10 ft from the wall where the monitor hangs; that is a typical machine-side distance, and you should measure your own. The legibility rule is 1 inch of capital letter height per 20 ft of viewing distance: the highway-signage figure is 30 ft per inch (FHWA legibility planning), and 20 ft per inch is the conservative choice for a value that gets a two-second glance. The candidates are 15-inch and 19-inch monitors with 16:9 panels, the size range you asked for. Last assumption: the project's largest text fills one tenth of the picture height once the view is scaled full screen; replace that fraction with your own. This is the same rule behind sizing a screen from viewing distance, pointed at a mirror instead of a sign.
Rule in words. Required letter height in inches equals the distance in feet divided by 20. Delivered letter height equals the monitor's picture height times the text fraction, and the reach is the delivered height multiplied back by 20.
Arithmetic. A 16:9 picture stands 9 / √(16² + 9²) of its diagonal tall, and √(16² + 9²) = 18.36, so picture height is 0.49 × diagonal.
- Required at 10 ft: 10 ÷ 20 = 0.5 in.
- 15-inch: picture height 15 × 0.49 = 7.35 in; letters 7.35 ÷ 10 = 0.735 in; reach 0.735 × 20 = 14.7 ft.
- 19-inch: picture height 19 × 0.49 = 9.3 in; letters 0.93 in; reach 0.93 × 20 = 18.6 ft.
Result. Both screens clear the 0.5 in requirement at 10 ft. The 15-inch delivers 0.735 in, about 1.5 times the requirement; the 19-inch delivers 0.93 in, about 1.9 times.
Decision. With the largest text near a tenth of the picture, a 15-inch monitor covers posts up to about 14 ft and a 19-inch up to about 18 ft. Take the 15-inch inside the first band and the 19-inch beyond it. Change the fraction and the reach moves with it: text at a twentieth of the picture halves both reaches, text at a fifth doubles them.
When to pick something else
Operators have to work the screens from the big station: skip the mirror and put real control there, either the panel itself or a PC running the HMI client. The PC route is its own project; setting up a PC as an HMI beside an operator panel with OPC walks through the data side, and using a PC monitor as a shop floor HMI display covers the screen choice.
The panel has neither remote access nor a documented video output: the browser path is closed, so the choice is a model with the feature or the PC client above.
The station should also show its own content, shift notices or targets: that is a signage job, and a signage display is the wrong tool for the live mirror. Ours play prepared images and video from their own storage and have no input that could receive your panel's screen. For a screen that runs its own playlist, start from our panel-mount display range.
What to ask for before you buy
- The panel model and the manual page that documents remote access, including whether a view-only setting exists.
- The reading distance in feet, so the 20 ft per inch rule sizes the monitor.
- The client computer's video output and the monitor's matching input, HDMI or DisplayPort at these sizes.
- A network drop at the station, or a switch port within 328 ft of the panel.
- How the computer and the monitor mount at the post, and who switches them on each shift.
- How many hours a day the screen is on. A consumer TV suits an office bench once its sleep timer is off and its input is locked; on the floor, an industrial monitor has those behaviours designed out.
Recommendation: show the panel's documented browser remote view on a small client computer, locked to view-only, whenever the station only needs to read. Size the screen at 1 inch of letter height per 20 ft of distance: with the project's largest text near a tenth of the picture height, that puts a 15-inch monitor on posts inside about 14 ft and a 19-inch on posts up to about 18 ft. Move to a PC-based HMI client when operators must control screens from that station, and to a single cable only when the panel's manual lists a monitor output.
Questions
Does the larger monitor need to be a touch screen?
No. The touch surface stays on the HMI panel, and with the remote view locked to display-only a touch overlay on the big screen would have nothing to press. A non-touch 15 to 19 inch monitor avoids that confusion and costs less than the touch version of the same size. Operators who need to push buttons walk to the panel.
Does the browser remote view need an internet connection?
No. The panel serves the view over the local Ethernet network, so the only requirement is that the computer and the panel reach each other on the machine or plant network. Keep the session on that network; a shop-floor picture has no reason to leave the site.
What if the HMI panel has no remote access feature?
Then the browser path is closed. Check the manual of the exact model for a documented monitor output; a few panel-PC class units list one, and a single cable does the whole job. With neither feature, a PC at the station running the HMI or SCADA client against the same controller data is the remaining route.
What kind of computer do I need at the station?
Anything that runs a browser and drives the monitor's native resolution: a thin client or a small PC. The load is one browser window, so processing demand is light. At a machine-side post, a sealed case with no cooling intake facing the dust and a mount that keeps the box off the floor are worth more than raw speed.
Can a consumer TV stand in for an industrial monitor?
At an office bench, yes. On the floor, check three things first: turn the TV's sleep timer off so the picture returns after a break, lock it to the computer's input so its own menus and pop-ups stay hidden, and hang it by its VESA hole pattern away from coolant spray and dust.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.