Projected capacitive is the default touch choice for interactive signs: multi-touch input, high clarity and scratch resistance with a bare finger. Choose analog resistive when users wear gloves or use an ordinary stylus. Choose surface acoustic wave when a public kiosk needs the clearest glass surface and stays dry.
When you order a touch screen for a sign, the sensing technology is not a footnote. It decides who can operate the sign, gloved hands or bare fingers, whether two fingers work at once, how the image looks through the panel, and how many touches the surface survives. This comparison covers the four methods you will be offered for sign-sized panels, analog resistive film, projected capacitive, surface capacitive and surface acoustic wave (SAW), plus two specials for large and pen-only jobs, and it ends with a decision for each case.
The answer: match the method to the hands on the glass
Bare fingers and customer self-service: order projected capacitive. It is the only one of the four that reads several touch points at once, and its glass front carries the highest rated touch count.
Gloves, an ordinary stylus, or written input: order analog resistive film. Pressure is all it senses, so a gloved hand, a plastic pen or a fingernail all register, and it costs the least of the four.
A public kiosk that must look sharp and stays dry: order surface acoustic wave. The surface is bare glass with the highest light transmittance of the four, it resists scratches better than capacitive glass, and it keeps working after a scratch. Keep water and insects off it, because a drop registers as a touch.
Everything else is a variant: surface capacitive is the lower-cost, single-touch cousin of projected capacitive for larger panels, infrared optical scales to the biggest sizes, and electromagnetic induction is pen-only and belongs to signature capture and drawing tablets.
How each method senses a touch
Analog resistive film. A glass plate and a plastic film, each carrying a transparent electrode coating, sit a narrow gap apart. A press pushes the two coatings into contact, current flows, and the controller reads the voltage at that point. Because pressure is the only input, any point works: finger, glove, stylus, pen.
Surface capacitive. A glass substrate carries one transparent electrode layer under a protective cover. Voltage applied at electrodes in the four corners sets up a uniform low-voltage field across the panel. A finger draws a tiny charge from the field, and the controller locates the touch from the change measured at the corners. Two simultaneous points defeat the structure, so treat every surface capacitive panel as single touch.
Projected capacitive. A pattern of many small transparent electrodes sits under an insulating glass or plastic cover, with the sensing chip behind it. A finger changes the electrostatic capacity of several electrodes at once, and the controller computes the position from the ratios between the resulting currents. Many electrodes mean several independent touch points. The count depends on the layout: self-capacitance designs track one or two points, and mutual designs track more. Indium-tin-oxide electrodes grow more resistive as the panel grows, which adds noise and error, so large projected capacitive panels replace etched electrodes with a grid of very thin wires.
Surface acoustic wave. Piezoelectric transducers in the corners of a glass panel send ultrasound waves across the surface, and transducers on the opposite sides receive them. A finger absorbs part of the wave, and the position follows from where the received signal dips. Nothing presses on the glass, so the viewing side carries no film and no electrode layer.
Two specials. Infrared optical panels run infrared LEDs and an image sensor along the top edge with retroreflective tape along the other edges; a touch casts a shadow and triangulation fixes its position, which is why the method scales to large panels. Electromagnetic induction panels read a special stylus that generates a magnetic field, giving pen precision and pressure sensing with no finger input at all.
Side-by-side comparison
Touch life ratings below come from vendor datasheets, which commonly quote 30 to 35 million touches for resistive film and 60 million or more for capacitive glass.
| Property | Analog resistive film | Projected capacitive | Surface capacitive | Surface acoustic wave |
|---|---|---|---|---|
| Input it accepts | Finger, glove, any stylus, handwriting | Bare finger or special capacitive stylus | Bare finger or special capacitive stylus | Finger or soft object that absorbs the wave; gloved finger works; special stylus only |
| Multi-touch | No, one press point | Yes, count set by electrode layout; self-capacitance tracks one or two points | No, single point by structure | Single point in common panels |
| Image clarity | Lowest, film plus two electrode layers in the light path | High | High | Highest, bare glass with nothing on the viewing side |
| Scratch behaviour | Film surface wears and marks | Glass front, a deep scratch can disturb the signal | Glass front | Glass resists scratches and stays sensitive afterwards |
| Drops and dust | Film covers the surface, dust and drops stay on top of it | Strong resistance to dust and drops | Strong resistance to dust and drops | A water drop or an insect registers as a touch |
| Rated touch life | 30 to 35 million touches | 60 million or more | 60 million or more | No touch wear, nothing presses the glass |
| Cost position | Lowest | Higher, more complex to make | Below projected | Mid, improving |
| Order it when | Gloves, styli, handwriting, hard use, tight budget | Customers tap, multi-touch, image clarity | Large single-touch panel on a budget | Dry indoor public kiosk, clarity first |
Where each technology wins
Projected capacitive: the customer-facing default. Self-order kiosks, wayfinding maps, queue check-in, salon and cafe menus that guests tap themselves. It gives real multi-touch, high image clarity and a scratch-resistant glass front rated for 60 million touches or more. Two things to plan around. Gloves will not operate it, and metal structures close to the panel can cause phantom touches. Heat brings the same behaviour, so before anyone replaces a touch layer for ghost touches, run the checks in ghost touch at high temperature: check before replacing.
Analog resistive: wherever gloves live. Machine terminals, punch stations, food and chemical lines where gloves are mandatory, paper forms and clipboards being replaced, signature and handwriting capture. It costs the least to buy and the least to replace after damage, and a shattered touch layer over a working image becomes broken HMI touch screen with a working LCD: repair or replace arithmetic. Plan the interface for single touch with big targets; a touch screen keyboard shift key on a single-touch panel shows the pattern.
Surface acoustic wave: clarity in dry public rooms. ATMs, ticket machines, library and lobby kiosks. Bare glass, the highest transmittance of the four, scratch resistance above the capacitive glass, and no touch wear because nothing presses the surface. It reads gloved fingers too, since the glove absorbs the wave just as a finger does. The weakness is exact: any water drop or stray insect on the surface registers as a touch, so SAW belongs indoors, away from splashes and condensation.
Surface capacitive and infrared: the large-panel options. Surface capacitive suits relatively large single-touch panels at a cost below projected. Infrared optical steps past the electrode limits completely, which is why it appears on the biggest touch surfaces.
Worked example: a gloved punch station
A machine shop replaces its paper time sheet with a touch screen at the door to the floor. Operators wear leather gloves. There are 50 operators across 3 shifts, and each touches the screen about 30 times per shift: clock in, clock out, confirm a job change.
Touch load: 50 × 3 × 30 = 4,500 touches per day. Over 250 working days: 4,500 × 250 = 1,125,000 touches per year.
Text size: the nearest user stands 24 in away, which is 2 ft. At the planning figure of 30 ft of viewing distance per inch of capital height (FHWA), minimum capitals are 2 ÷ 30 = 0.067 ft, which is 0.8 in. For fast reading at 20 ft per inch, size the capitals at 2 ÷ 20 = 0.1 ft, which is 1.2 in, with line spacing of 1.7 × 1.2 = about 2 in.
Decision: gloves rule out both capacitive types, which read the electrostatic capacity of a bare hand. The screen hangs beside the outside door, where morning condensation forms, so SAW is out too; a film of water on the glass registers as touches. That leaves analog resistive. Its 30 to 35 million touch rating spans 30,000,000 ÷ 1,125,000 = 26.7 to 31.1 years at this rate, so the touch count will never be the reason this panel stops working; film wear will, and film wear is visible and repairable. Order resistive film, size the targets for gloved fingers, and put the 1.2 in capitals behind it; the clarity penalty costs nothing at that text size.
If the same screen also carries line status next to the punch buttons, the andon board guide covers where a small screen fits on a shop floor.
What to ask for before you order
Ask the vendor for four things, in this order.
- The sensing technology by name. Touch screen alone is not a specification. Insist on projected capacitive, surface capacitive, analog resistive film or surface acoustic wave in writing.
- The front material. Glass or film decides the clarity and scratch rows of the table above. If you fit a protective cover on top, its finish changes how small text reads; the anti-glare cover sharpness fix shows by how much.
- The rated touch count from the datasheet, so you can divide it by your own touches per day the way the example above does.
- Glove and stylus behaviour with your own gloves. Bring the gloves the floor actually uses. A thin disposable glove may pass on a projected panel tuned for sensitivity; a heavy work glove will not.
Touch type is an order option on our touch displays, listed size by size with the touch choices for each. Whichever panel you choose, power it up and load a test page before it goes on the wall; the HMI panel startup and runtime check says what to time and what to reject.
The decision
Recommendation: Specify projected capacitive for any sign that customers touch with bare fingers; it is the only method here that delivers multi-touch, and its 60 million or more rated touches sits well above the 30 to 35 million resistive rating. Specify analog resistive film whenever gloves, an ordinary stylus or written input must work, or when the front gets wet, dusty or knocked, and accept its lower clarity. Keep surface acoustic wave for dry indoor public kiosks where image clarity is the point, and keep drops, condensation and insects off the glass. Use surface capacitive for large single-touch surfaces where projected is over budget, and leave infrared optical and electromagnetic induction to the very large and the pen-only jobs.
Get the touch method settled at order time. It is the one line of the quote you cannot change afterwards.
Questions
Why does an ordinary stylus do nothing on a capacitive screen?
Capacitive sensing reads the small electrostatic capacity of a conductive object, and a human finger is the usual one. A plastic pen carries no charge, so the controller sees nothing. A capacitive stylus has a conductive tip that mimics a finger. Resistive and infrared panels read pure pressure or a blocked beam, so almost any rigid point works on them.
Which touch panel type lasts the longest?
Datasheets commonly rate capacitive glass at 60 million touches or more and resistive film at 30 to 35 million. Surface acoustic wave glass has no touch wear at all, because nothing presses on it. At a counter kiosk rate of 500 touches a day, even the resistive rating spans about 164 years, so film surface wear, the backlight and the bezel age first. Inspect the film surface on resistive panels as part of routine cleaning.
Can a metal frame or heat cause false touches on a capacitive panel?
Yes. Projected and surface capacitive panels react to nearby metal structures, so a bracket tight against the panel edge can create phantom touches. Heat does the same: a panel that starts ghost-touching as its enclosure warms should have its surface temperature measured before the touch layer is blamed or replaced. Leave whatever clearance the maker's installation notes call for, and load brackets onto the bezel, not the glass.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.