Comparison

Video tachometer vs Duct Sensor Assistant

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

Head to head
About

Video tachometer

This app uses slow-motion video to create a strobe light effect, allowing you to measure rotational speeds. It records video with detailed information like frame rate and exposure, and offers customizable text overlays.

Highlights
  • Strobe light effect simulation
  • Rotational speed measurement (RPM/Hz)
  • Slow-motion video recording
  • Customizable text overlays on video
  • Adjustable frame rate and exposure
  • Records 4K video (if supported)
Read full description

When the frame rate of a video matches the speed of a particular part, the effect is the same as using a strobe light. In the video, that part freezes. Since the frame rate of a video can be adjusted, this effect can be used to determine the rotational speed of a part. The smartphone must support slow-motion video recording (filming at a high frame rate). This is the case for all smartphones starting with iPhone 5S. The range is as follows: • 0.5—240 Hz (30—14400 RPM), for all phones from iPhone 6 onward • 0.5—120 Hz (30—7200 RPM), for iPhone 5S THE HERTZ (Hz) VALUE IS MORE ACCURATE THAN THE REVOLUTIONS PER MINUTE (RPM) VALUE, SINCE REVOLUTIONS PER MINUTE ARE CALCULATED FROM HERTZ AND ROUNDING IS DONE. To get a clear image, good lighting is important. The clarity of the image is controlled by the exposure of the video (exposure time and light sensitivity (ISO)). If the exposure time is reduced, the image will increase in clarity, but brightness will lower. To increase the brightness, you need to raise the camera's light sensitivity (ISO), but then the amount of noise increases. You also need to manually adjust the focus of the camera. The app can record video. The video format depends on the selected format in the app settings. If your iPhone supports 4K video format (3840x2160), then you can record 4K video at the frame rate supported by your iPhone. Text with important information is added to the frames of the recorded video: the selected frame rate, exposure duration, ISO, time stamp, time difference between the current and previous frames (Tcurr. − Tprev.), the sequence number of the frame in the recorded video. If you want any other information to be added, then let me know. You can choose to add only part of this information, and you can choose a different text color. You also have the option of not adding any information. You can change the information that is added and the color of the text while recording a video. At high frame rates, frames that do not have time to be processed may be discarded. This does not affect subsequent frames and can be controlled using the time difference between the current frame and the previous frame (Tcurr. − Tprev.). Dropping frames affects the video frame rate displayed in the "Photos" app. But the time interval between frames that were taken one after another and were not discarded will correspond to the selected frame rate. Frames may be dropped even when shooting slow motion video using the "Camera" app. You can check this by looking at the frame rate for slow motion video in the "Photos" app. Video containing the app's interface can be captured using the iOS "Screen Recording" function. The app can take a photo with the measurement result, date, and time written on the photo. The exposure time and ISO settings will be saved in the photo's metadata. To take a photo that shows the app interface, tap the "Pause" button and take a screenshot. It is possible to choose a video format that has the best quality, but has a significantly lower maximum frame rate. The difference between the formats is clearly visible only when using the digital zoom. Also, when using a format with better quality, the Rolling Shutter effect is stronger. Therefore, the best quality format can be used at speeds less than about 2000 rpm. You can turn on hints for easier observation of changes in rotation speed. Hints show how to change the frame rate (decrease or increase) depending on the direction of rotation of the mark. The hints are selected manually, but then you do not need to remember this information. The hints are relevant for frequencies close to the rotation frequency. If the direction of rotation of the impeller is known, hints can be selected in advance. The arrow showing the direction of rotation of the impeller must correspond to the "+" button. The video tachometer measures the rotational speed in exactly the same way a stroboscopic tachometer would.

About

Duct Sensor Assistant

Features
Read full description

Via the Belimo Duct Sensor Assistant App it is possible to extend the range of use and to adapt the configuration individually to application requirements. A Bluetooth® dongle is required for configuration via the Belimo Duct Sensor Assistant App (sold separately, A-22G-A05). Features: • Communication via Bluetooth BLE • Bluetooth Dongle A-22G-A05 required, which will communicate with the sensor via a Micro-USB-connector • Can be used for the following sensors: 22ADP-.., 22DTH-..5.., 22DTH-..6.., 22DC-..3, 22DTC-.., 22DTM-.., 22DCV-.., 22DCM-.., 22DCK-.., 22UTH-..50X, 22UTH-..60X • Supported languages DE, EN, FR, IT, ES, PT Configuration options: • Individual configuration of output signals • Setting of different measuring ranges • Additional adjustment of offset values • Parameterization of Live-Zero-Signal (2..10 V etc.) and the system of units • Setting options for display indications • Customized parameterization of traffic-light function (TLF) • Extension of the physical bus address • Store settings on the mobile device and load on other sensors • Representation and output of the differential pressure as a volume flow value

Screenshots

Video tachometer4 screens
Duct Sensor Assistant4 screens

Verdict

The call

The clearest difference is in-app purchases: Duct Sensor Assistant at none against Video tachometer's 1. Duct Sensor Assistant also leads on iOS requirement (12.0 vs 15.6). On price, update cadence, ads and device support 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

Both are free to download. Video tachometer sells 1 one-off in-app purchase. Duct Sensor Assistant asks for nothing beyond the download.

UpkeepUpdate frequency

Video tachometer ships an update every 3 months, Duct Sensor Assistant every 6 months. The most recent releases landed on September 21, 2026 and September 16, 2026 respectively.

Scorecard2 real differences · 8 level
Video tachometer versus Duct Sensor Assistant: the parameters behind the verdict, then further details
ParameterVideo tachometerDuct Sensor Assistant
PriceFreeFree
Rating4.6 (84 ratings) — better—
Positive reviews84.6% of reviews—
Number of ratings84 — better—
Update frequencyEvery 3 months — betterEvery 6 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.612.0 — better
Further details — not scored
Size5 MB31 MB
Age rating4+4+
DeveloperDmitriy KharutskiyBELIMO Automation AG

Bugs and requests

Video tachometer

Reported bugs

3 issues
  • Does not read anything
  • Pop-ups for paid features
  • Interface visible in screen recording

Requested features

4 requests
  • Ability to record video
  • Slow phase shift mode
  • Improved UI for initial setup
  • Long press for gradual increment/decrement

Duct Sensor Assistant

Not enough reviews yet to summarise bugs or requests.

In-app purchases

1 purchases

Video tachometer

One-time1
  • Full version$2.99
None

Duct Sensor Assistant

No in-app purchases

Questions

Is Video tachometer free?
Video tachometer is free to download, with in-app purchases available.
Is Duct Sensor Assistant free?
Duct Sensor Assistant is free to download, with no in-app purchases.
Do Video tachometer or Duct Sensor Assistant have ads?
Neither Video tachometer nor Duct Sensor Assistant shows ads.
Which is updated more often, Video tachometer or Duct Sensor Assistant?
Video tachometer ships an update every 3 months, and Duct Sensor Assistant every 6 months. Most recently, Video tachometer was updated on September 21, 2026 and Duct Sensor Assistant on September 16, 2026.

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