Comparison

RTD Reference vs Units App

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

Head to head
About

RTD Reference

Instantly convert resistance to temperature and vice versa for over 70 RTD types and 9 popular thermistors. This tool uses precise algorithms for accurate calculations, ideal for field technicians and engineers.

Highlights
  • Resistance to temperature conversion
  • Temperature to resistance conversion
  • Support for 70+ RTD types
  • Support for 9 popular thermistor types
  • Uses Steinhart-Hart and Callendar-Van Dusen formulas
  • Accurate 64-bit double precision math
  • Customizable display colors and sounds
Features
Read full description

This application is a simple, fast, and comprehensive tool for field technicians, engineers and programmers to quickly and easily convert resistance to temperature and vice versa for many popular temperature sensing devices. It includes support for over 70 types of RTDs (Resistance Temperature Detectors) and 9 types of popular Thermistors (Thermal Resistors). These devices exhibit predictable changes in their resistance depending on their ambient temperature, a characteristic that makes them useful for measuring temperature in many residential, commercial and industrial applications. Merely select your entry mode (resistance in ohms or temperature in deg F or C) and your RTD or Thermistor type. Your entries are converted to the other two units instantly as you type. The app supports: Platinum RTDs – 56 combinations of reference resistance and alphas Copper RTDs - 4 combinations of reference resistance and alphas Nickel RTDs - 8 combinations of reference resistance and alphas Nickel-Iron RTDs (Balco) - 6 combinations of reference resistance and alphas Thermistors – 9 popular types including two types of 10K thermistors Although the behavior of RTDs and Thermistors is predictable, they are not linear. This app uses the Steinhart-Hart formula for Thermistor calculations, the Callendar-Van Dusen formula for Platinum RTDs and similar algorithms for the other types of RTDs. All formulas and coefficients used by the app are described in the documentation provided with the app. A number of lookup charts are included showing resistance vs temperature for many of the most popular types of RTDs. The app uses 64-bit double precision math to provide the best possible resolution and accuracy for its calculations. However, since the algorithms are curve-fitting approximations, there will certainly be some points at which there are very small (usually insignificant) differences between the calculated values and a manufacturer’s published data table. You can use the Settings application to change background and text colors, change keyclick sounds, and adjust keyclick volume. Please send any comments, suggestions or corrections to support@dohmann.com

About

Units App

Easily convert between various units across multiple categories including length, temperature, and weight. Access past conversions through a history list and send calculations via email. Supports a wide range of Apple devices.

Highlights
  • Multiple unit categories
  • Metric and imperial systems
  • Conversion history
  • Send calculations via email
  • iPad multitasking support
Features
Read full description

Convert between many units from several categories and different unit systems (metric, imperial, ...). Features: - categories: length, temperature, capacity, weight, energy, power, pressure, area - access previous conversions from the history list - categories have different colors (in the history as well) - flip units - send calculations by email - support for the iPhone 6 and 6+ - support for the iPad multitasking (split view..)

Screenshots

RTD Reference4 screens
Units App4 screens

Verdict

The call

The clearest difference is rating: RTD Reference at 5.0 against Units App's 2.0. Units App's advantage is price ($0.99 vs $3.99). On ratings volume, update cadence, ads and in-app purchases 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

RTD Reference costs $3.99 and Units App $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

RTD Reference holds the better App Store score, 5.0 against 2.0. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

UpkeepUpdate frequency

RTD Reference ships an update every 8 months, Units App every 9 months. The most recent releases landed on September 25, 2026 and October 1, 2026 respectively.

Scorecard2 real differences · 8 level
RTD Reference versus Units App: the parameters behind the verdict, then further details
ParameterRTD ReferenceUnits App
Price$3.99$0.99 — better
Rating5.0 (1 ratings) — better2.0 (1 ratings)
Positive reviews50.0% of reviews—
Number of ratings11
Update frequencyEvery 8 months — betterEvery 9 months
AdsNoNo
In-app purchasesNoNo
MonetizationPaidPaid
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS12.012.0
Further details — not scored
Size5 MB2 MB
Age rating4+4+
DeveloperDohmann Engineering ServicesPiet Jonas

Customer experience

RTD Reference

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews2 reviews
Positive50.0%
Neutral0.0%
Negative50.0%

Units App

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%

In-app purchases

None

RTD Reference

No in-app purchases

None

Units App

No in-app purchases

Questions

Is RTD Reference free?
RTD Reference costs $3.99, with no in-app purchases.
Is Units App free?
Units App costs $0.99, with no in-app purchases.
Which has better reviews, RTD Reference or Units App?
RTD Reference is rated higher. RTD Reference averages 5.0 out of 5 from 1 ratings, while Units App averages 2.0 from 1 ratings.
Do RTD Reference or Units App have ads?
Neither RTD Reference nor Units App shows ads.
Which is updated more often, RTD Reference or Units App?
RTD Reference ships an update every 8 months, and Units App every 9 months. Most recently, RTD Reference was updated on September 25, 2026 and Units App on October 1, 2026.

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