Video tachometer 4+

Strobe light effect, RPM meter

Dmitriy Kharutskiy

    • 4.7 • 61 Ratings
    • Free
    • Offers In-App Purchases

iPhone Screenshots

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.

To take a photo with the result of the measurement written on it, press 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 1000 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.

What’s New

Version 2.0

• Video recording. 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, 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.
• Bug fixes.

Ratings and Reviews

4.7 out of 5
61 Ratings

61 Ratings

mtc-xyzzy ,

Works beautifully!

I used this to check the accuracy of the engine tachometer in my Cessna 172 airplane. I was checking “static RPM” (wide-open throttle with brakes set on the ground) and found it to be lower than spec, which was concerning. I checked with the shop and they had measured it at 2306 which is to spec. The tach indicated only 2200. Using this, I measured 2310 (I had not yet upgraded to the full version allowing adjustments of 1) which confirmed the shop’s findings and made me feel a lot better about the engine’s output. Very happy with the app!

ammarlow ,

Very Helpful

I acquired an old Snapper riding lawnmower that was reving very high until I adjusted the governor down. I wanted to verify the engine RPM was in a good spot, so I thought about the Tachometer RPM testers I use at work and started wondering if my iPhone camera could check RPM. Sure enough I found this! This app helped confirm that the old powerful little engine was running at the factory rating of 3300 RPM. I was very impressed by the app and how easy it was to use. Wish I could download it for the first time again. 5 stars

John_in_WI ,

Finally, one that works!

I’ve tried several apps that use the camera’s flashlight as the timing mechanism, which works fine if you’re in a darkroom and can be within 4” of your mark. Those apps have long since been deleted. Using the video frames per second is the way to go and now you can actually see your mark to know if you have your frequency set right. Thank you! Thank you! Thank you! This is the one you want.

App Privacy

The developer, Dmitriy Kharutskiy, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More

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