Comparison

ASHRAE Psychrometric Chart vs Duet Display

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

ASHRAE Psychrometric Chart

This interactive tool allows users to plot and customize psychrometric charts on their iPad. Easily create and save HVAC process graphs, update properties dynamically, and share charts and data via email. Supports both IP and SI units.

Highlights
  • Interactive psychrometric chart plotting
  • Customizable chart appearance
  • Dynamic property updates
  • Create and edit points and labels
  • Email charts and data
  • Unlimited projects and templates
  • Zoom and pinch functionality
Features
Read full description

The HVAC Psychrometric Chart app is the first truly interactive graphical psychrometric chart for the iPad, and it includes both IP and SI units. It is now optimized for iOS 16. Using your finger, you can easily plot HVAC and other psychrometric processes on the iPad screen while you are out in the field, save the graphs, and then email the graph and results to yourself or clients. The HVAC Psych Chart app includes the following features and functionality: 1. Displays a fully customizable psychrometric chart in both landscape and portrait modes. 2. Allows you to customize the graph in many different ways including specifying the psychrometric chart line colors, chart background color, hide/display status of chart lines, point colors, process line colors, units of graph values, and the min/max limits of the chart. 3. Using your finger, you can plot as many points as you want on the screen. As you move your finger around the graph, the psychrometric properties at the top of the screen dynamically update . In addition, you can double-tap a point to display the point properties and then edit them. 4. Create psychrometric processes by plotting points then connecting them with process lines. Also, create custom labels anywhere on the chart. 5. After you have completed creating the chart, you can email a list of all the points and their properties along with a PDF of the chart, itself. 6. Create an unlimited number of psychrometric chart projects. Also, you can create templates that you can reuse over and over again. 7. Zoom in or out of the chart by "pinching" the iPad screen so as to view items in more detail. 8. Display sensible heat ratio (SHR) line 9. Display psych process line as curved along 100% RH line.

About

Duet Display

Transform your iPad or iPhone into an advanced, lag-free extra display for your Mac or PC. Interact with your computer using touch and gestures, and unlock professional drawing capabilities with Apple Pencil support.

Highlights
  • Extra display for Mac & PC
  • Lag-free performance
  • Touch and gesture support
  • Apple Pencil integration
  • Professional drawing tools
  • Portable productivity
Read full description

#1 best-selling iPad app in US, Japan, UK, Germany, and 17 other countries! Duet turns your iPad or iPhone into the most advanced extra display for your Mac & PC. Developed by a team of ex-Apple engineers, Duet offers unparalleled performance and display quality - all with zero lag. — DO MORE — Be twice as productive by multitasking with two screens. And for those that travel, have a portable way to stay productive. — INCREDIBLY SIMPLE — To get started, plug your iPad into your desktop using your charging cable. The free Duet desktop app will automatically detect your device, and transform it into a high performance touchscreen display. There’s no need to worry about unreliable Wi-Fi, laggy performance, pixelated screens or managing network passwords. — TOUCHSCREEN — Interact with Mac & PC like never before, with touch & gestures, including two-finger scrolling, pan and zoom. And with our latest release, you can even add a touch bar to any iPad with any Mac. — PERFECT FOR APPLE PENCIL — With Duet Pro, you can turn your iPad and Apple Pencil into a professional graphics tablet. We’ve re-engineered our rendering algorithms for ultra-responsive drawing, optimized specifically for designers, illustrators and artists. Duet Pro also unlocks pressure & tilt sensitivity, hover, palm rejection, and more to seamlessly draw in the most powerful programs for professionals. Get precise control in Photoshop, Corel Painter, Lightroom, ToonBoom, Illustrator, Manga Studio and more.  — PRESS — TechCrunch - "Feels Like Magic" TIME - "Getting Work Done Faster and More Efficiently" The Guardian - "Lag-free" Forbes - "The simple thing to note is this...Duet Display works." The Verge - "Glorious Fluidity" Lifehacker - "It's fast, easy to use, and works great" Business Insider - "Zero lag and true retina resolution” Wall Street Journal - “It’s as easy as just plugging it in" — REVIEWS — “Awesome! My iPad Pro can be an extra monitor! Cool app” ~CEO of T-Mobile, John Legere “Very smooth and responsive indeed, plus you could use the touch screen to “click” on screen interfaces!” ~Photographer, Lok Cheung “Love the ability to use my iPad as a monitor with Duet.” ~Former Chief Evangelist of Apple, Guy Kawasaki “Just started using this app called Duet… Kinda love it so far.” ~Comedian and Youtube, Phillip DeFranco “All my mac folks look at the Duet app… GREAT!” ~Actor and Comedian, Sinbad  "I really like the app, I suppose the biggest compliment I can give is that it's so easy to setup it almost seems like an Apple product.” ~Early Adopter, M. Nightingale "Amazing solution for me by the way. Works as I was hoping for and actually my main reason for getting an iPad : )” ~Early Adopter, M. Gemzoe Duet Works With: All iPhones and iPads with iOS 7.0 and later All Macs with 10.9 (Mavericks) and later All PCs with Windows 7 and later Duet Pro Works With: All iPad Pros with Apple Pencil All Macs with 10.9 (Mavericks) and later All PCs with Windows 8.1 and later (64 bit) Duet Pro is an optional upgrade for additional features, and price may vary by location. Duet Pro subscriptions will be charged to your credit card through your iTunes account. Your subscription will automatically renew unless canceled at least 24 hours before the end of the current period. You will not be able to cancel the subscription once activated. Manage Duet Pro in Account Settings after the optional upgrade. Learn more at http://www.duetdisplay.com Terms: https://www.duetdisplay.com/help-center/duet-terms-and-conditions Privacy Policy: https://www.duetdisplay.com/help-center/duet-privacy-policy

Screenshots

Duet Display3 screens

Verdict

The call

The clearest difference is price: Duet Display at Free against ASHRAE Psychrometric Chart's $19.99. Duet Display also leads on update cadence (every 3 weeks vs every 11 months) and review sentiment (45% vs 27%). ASHRAE Psychrometric Chart's advantage is in-app purchases (none vs 6) and ads (none vs shown). On iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Duet Display is free to download; ASHRAE Psychrometric Chart costs $19.99 up front. Duet Display sells 6 in-app purchases, starting at $3.99 per month. ASHRAE Psychrometric Chart asks for nothing beyond the download.

UpkeepUpdate frequency

ASHRAE Psychrometric Chart ships an update every 11 months, Duet Display every 3 weeks. The most recent releases landed on October 12, 2026 and October 31, 2026 respectively.

Scorecard7 real differences · 3 level
ASHRAE Psychrometric Chart versus Duet Display: the parameters behind the verdict, then further details
ParameterASHRAE Psychrometric ChartDuet Display
Price$19.99Free — better
Rating—4.4 (49K ratings) — better
Positive reviews27.3% of reviews45.5% of reviews — better
Number of ratings—49K — better
Update frequencyEvery 11 monthsEvery 3 weeks — better
AdsNo — betterYes
In-app purchasesNo — betterYes
MonetizationPaidFree with in-app purchases — better
DevicesiPadiPhone, iPad, iPod, Vision Pro — better
Requires iOS13.013.0
Further details — not scored
Size2 MB59 MB
Age rating4+4+
DeveloperASHRAE, Inc.Duet, Inc.

Customer experience

ASHRAE Psychrometric Chart

Written reviews11 reviews
Positive27.3%
Neutral27.3%
Negative45.5%

Duet Display

All ratings48,776 ratings
Positive86.2%
Neutral3.1%
Negative10.7%
Written reviews2,386 reviews
Positive45.5%
Neutral6.7%
Negative47.9%

Bugs and requests

ASHRAE Psychrometric Chart

Not enough reviews yet to summarise bugs or requests.

Duet Display

Reported bugs

3 issues
  • Incompatibility with certain software and drivers
  • Laggy performance and input delays
  • Unreliable connection and frequent disconnects

Requested features

4 requests
  • Improved resolution and scaling options
  • Better support for older devices and Windows
  • More customization and control over settings
  • Wireless connectivity without subscription

In-app purchases

None

ASHRAE Psychrometric Chart

No in-app purchases

6 purchases

Duet Display

Subscriptions6
  • Duet Starter (Monthly)$3.991 Month
  • Duet Air (Monthly)7 Days trial$5.991 Month
  • Duet Pro7 Days trial$7.991 Month
Show 3 more
  • Duet Starter (Annual)$39.991 Year
  • Duet Air (Annual)7 Days trial$49.991 Year
  • Duet Pro (Annual)7 Days trial$79.991 Year

Questions

Is ASHRAE Psychrometric Chart free?
ASHRAE Psychrometric Chart costs $19.99, with no in-app purchases.
Is Duet Display free?
Duet Display is free to download, with in-app purchases available.
Do ASHRAE Psychrometric Chart or Duet Display have ads?
Duet Display shows ads; ASHRAE Psychrometric Chart does not.
Which is updated more often, ASHRAE Psychrometric Chart or Duet Display?
ASHRAE Psychrometric Chart ships an update every 11 months, and Duet Display every 3 weeks. Most recently, ASHRAE Psychrometric Chart was updated on October 12, 2026 and Duet Display on October 31, 2026.

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