Comparison

KD Serials vs Four

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

Head to head
About

KD Serials

Features
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KD series volt-ampere meter is a new type of coulomb meter that can measure various physical parameters such as voltage, current, power, charge and discharge capacity, remaining time, etc. At the same time, parameters can also be set to achieve full capacity voltage, zero capacity voltage, low capacity alarms, etc. Features. The meter can automatically identify the direction of the current, and can monitor the battery capacity in real time and use a broken code liquid crystal display. The measured data display information is comprehensive and user-friendly.

About

Four

Features
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1. After logging in to the APP, you can simultaneously view the devices installed in the sensor cloud platform; 2. After the account obtains the corresponding permissions, it can edit and delete the installed equipment and other management operations; 3. After switching the video device, you can view, play back and capture the installed video device in real time; 4. When the device has an alarm, the alarm will be displayed in the device alarm column, and it will also be pushed to the mobile phone through the message; 5.The APP also provides functions such as notification announcement, message setting, language setting, beginner's guide, and personal information editing.

Screenshots

KD Serials2 screens
Four3 screens

Verdict

The call

The clearest difference is update cadence: KD Serials at every 4 weeks against Four's every 2 months. KD Serials also leads on iOS requirement (9.0 vs 12.0). On price, ads, in-app purchases 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. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

KD Serials ships an update every 4 weeks, Four every 2 months. The most recent releases landed on October 1, 2026 and October 14, 2026 respectively.

Scorecard2 real differences · 4 level
KD Serials versus Four: the parameters behind the verdict, then further details
ParameterKD SerialsFour
PriceFreeFree
Update frequencyEvery 4 weeks — betterEvery 2 months
AdsNoNo
In-app purchasesNoNo
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS9.0 — better12.0
Further details — not scored
Size39 MB58 MB
Age rating4+17+
DeveloperHangzhou Junce Instruments Co., Ltd.Xiamen Sixin IoT Technology Co., Ltd.

In-app purchases

None

KD Serials

No in-app purchases

None

Four

No in-app purchases

Questions

Is KD Serials free?
KD Serials is free to download, with no in-app purchases.
Is Four free?
Four is free to download, with no in-app purchases.
Do KD Serials or Four have ads?
Neither KD Serials nor Four shows ads.
Which is updated more often, KD Serials or Four?
KD Serials ships an update every 4 weeks, and Four every 2 months. Most recently, KD Serials was updated on October 1, 2026 and Four on October 14, 2026.

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