RTD Reference vs Units App
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
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.
- 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
Read full descriptionHide 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
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.
- Multiple unit categories
- Metric and imperial systems
- Conversion history
- Send calculations via email
- iPad multitasking support
Read full descriptionHide 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
Verdict
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
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.
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.
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.
| Parameter | RTD Reference | Units App |
|---|---|---|
| Price | $3.99 | $0.99 — better |
| Rating | 5.0 (1 ratings) — better | 2.0 (1 ratings) |
| Positive reviews | 50.0% of reviews | — |
| Number of ratings | 1 | 1 |
| Update frequency | Every 8 months — better | Every 9 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 12.0 | 12.0 |
| Further details — not scored | ||
| Size | 5 MB | 2 MB |
| Age rating | 4+ | 4+ |
| Developer | Dohmann Engineering Services | Piet Jonas |
Customer experience
RTD Reference
Units App
In-app purchases
RTD Reference
No in-app purchases
Units App
No in-app purchases




