# 4 vs PID Controller Simulation

The clearest difference is price: 4 at Free against PID Controller Simulation's $3.99. PID Controller Simulation's advantage is update cadence (every 3 months vs every 11 months) and iOS requirement (13.0 vs 15.6). On rating, ratings volume, ads and in-app purchases there is nothing between them.

4 is free to download; PID Controller Simulation costs $3.99 up front. Neither carries in-app purchases, so what you see is what you pay.

On the App Store both sit at effectively the same score — 3.0 for 4 against 3.0 for PID Controller Simulation. Both are backed by a comparable volume of ratings — 2 and 2 respectively.

4 ships an update every 11 months, PID Controller Simulation every 3 months. The most recent releases landed on September 29, 2026 and October 9, 2026 respectively.

## The numbers

| Metric | 4 | PID Controller Simulation |
| --- | --- | --- |
| Price | **Free** | $3.99 |
| Rating | [3.0 (2 ratings)](https://appshunter.io/ios/app/4-20-temperature-calculator/id1602351736/reviews) | [3.0 (2 ratings)](https://appshunter.io/ios/app/pid-controller-simulation/id6612009107/reviews) |
| Number of ratings | 2 | 2 |
| Positive reviews | — | 33.3% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 11 months | **Every 3 months** |
| Monetization | **Free** | Paid |
| Size | 30 MB | 6 MB |
| Requires iOS | 15.6 | **13.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Mantas Kamarauskas](https://appshunter.io/developer/975306268) | [立娜 王](https://appshunter.io/developer/1761096632) |

## What reviewers say

### 4

[App page](https://appshunter.io/ios/app/4-20-temperature-calculator/id1602351736)

This utility app converts between 4-20 mA current signals and temperature readings. It's designed for engineers and technicians to quickly check transmitter scaling, verify loop values, and troubleshoot signal issues in various industrial applications.

**Highlights:** Two-way current to temperature conversion, Custom min/max process range, Support for negative temperatures, Celsius and Fahrenheit support, Fast and clean interface

**Features:** macOS Compatibility

**In-app purchases:** none


### PID Controller Simulation

[App page](https://appshunter.io/ios/app/pid-controller-simulation/id6612009107)

Master PID control theory and practice with this comprehensive simulation platform. Learn fundamental concepts, tune parameters, and simulate real-world applications like temperature and motor speed control. Export PID parameters as production-ready code in multiple languages.

**Highlights:** Comprehensive tutorial system, Interactive scenario simulations, Performance analysis tools, Code generator for multiple languages, Real-time curve visualization, Advanced PID algorithm explanations

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is 4 free?

4 is free to download, with no in-app purchases.

### Is PID Controller Simulation free?

PID Controller Simulation costs $3.99, with no in-app purchases.

### Which has better reviews, 4 or PID Controller Simulation?

4 and PID Controller Simulation are both rated 3.0 out of 5 on the App Store, from 2 and 2 ratings respectively.

### Do 4 or PID Controller Simulation have ads?

Neither 4 nor PID Controller Simulation shows ads.

### Which is updated more often, 4 or PID Controller Simulation?

4 ships an update every 11 months, and PID Controller Simulation every 3 months. Most recently, 4 was updated on September 29, 2026 and PID Controller Simulation on October 9, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*