# 4 vs Nellin controllers

The clearest difference is update cadence: Nellin controllers at daily against 4's every 11 months. 4's advantage is device support (3 vs 1). On price, ads, in-app purchases and iOS requirement there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

4 ships an update every 11 months, Nellin controllers daily. The most recent releases landed on November 3, 2026 and November 6, 2026 respectively.

## The numbers

| Metric | 4 | Nellin controllers |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.0 (2 ratings)](https://appshunter.io/ios/app/4-20-temperature-calculator/id1602351736/reviews)** | — |
| Number of ratings | **2** | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 11 months | **Daily** |
| Monetization | Free | — |
| Size | 30 MB | 38 MB |
| Requires iOS | **15.6** | 16.4 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 17+ |
| Developer | [Mantas Kamarauskas](https://appshunter.io/developer/975306268) | [Aleksandr Liashov](https://appshunter.io/developer/1881074623) |

## 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


### Nellin controllers

[App page](https://appshunter.io/ios/app/nellin-controllers/id6801412782)

**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 Nellin controllers free?

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

### Do 4 or Nellin controllers have ads?

Neither 4 nor Nellin controllers shows ads.

### Which is updated more often, 4 or Nellin controllers?

4 ships an update every 11 months, and Nellin controllers daily. Most recently, 4 was updated on November 3, 2026 and Nellin controllers on November 6, 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.*