# Milking Prep Lag Timer vs HMI Viewer

The clearest difference is update cadence: HMI Viewer at every 2 months against Milking Prep Lag Timer's every 6 months. HMI Viewer also leads on price ($0.99 vs $2.99) and device support (4 vs 1). On ads, in-app purchases and iOS requirement there is nothing between them.

Milking Prep Lag Timer costs $2.99 and HMI Viewer $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Milking Prep Lag Timer ships an update every 6 months, HMI Viewer every 2 months. The most recent releases landed on September 19, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | Milking Prep Lag Timer | HMI Viewer |
| --- | --- | --- |
| Price | $2.99 | **$0.99** |
| Rating | — | **[5.0 (4 ratings)](https://appshunter.io/ios/app/hmi-viewer/id1261910446/reviews)** |
| Number of ratings | — | **4** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 6 months | **Every 2 months** |
| Monetization | — | Paid |
| Size | 6 MB | 17 MB |
| Requires iOS | 15.6 | **15.0** |
| Devices | iPad | **iPhone, iPad, iPod, Mac** |
| Age rating | 4+ | 4+ |
| Developer | [University of Wisconsin - Madison School of Veterinary Medicine](https://appshunter.io/developer/871872159) | [Greg Maendel](https://appshunter.io/developer/507756979) |

## What reviewers say

### Milking Prep Lag Timer

[App page](https://appshunter.io/ios/app/milking-prep-lag-timer/id1105510997)

**In-app purchases:** none


### HMI Viewer

[App page](https://appshunter.io/ios/app/hmi-viewer/id1261910446)

This application allows end users to interact with PLC-controlled processes through custom-designed Human Machine Interfaces. Integrators can create and deploy these interfaces securely, enabling seamless control and monitoring of industrial systems.

**Highlights:** View-only HMI interface, Interact with PLC-controlled processes, Secure deployment to end-user devices, Supports major PLC brands, Native application performance

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Milking Prep Lag Timer free?

Milking Prep Lag Timer costs $2.99, with no in-app purchases.

### Is HMI Viewer free?

HMI Viewer costs $0.99, with no in-app purchases.

### Do Milking Prep Lag Timer or HMI Viewer have ads?

Neither Milking Prep Lag Timer nor HMI Viewer shows ads.

### Which is updated more often, Milking Prep Lag Timer or HMI Viewer?

Milking Prep Lag Timer ships an update every 6 months, and HMI Viewer every 2 months. Most recently, Milking Prep Lag Timer was updated on September 19, 2026 and HMI Viewer on October 24, 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.*