uSpectrum MK350N vs RPN
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
uSpectrum MK350N
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MK350 is using advanced spectroscopic technique architecture; therefore, the measurement accuracy is better than traditional color sensors. Traditional spectrometer needs to use PC or notebook for data analysis, UPR RD Team combines all functions into MK350 to let users process data analysis operation easily. MK350 is a cost-effective LED Meter which provides CRI、CCT、LUX、λp、Spectrum、CIE x,y 6 major functions. The light weight design and the measurement data which appear instantly without computer connection solutions both enhance the usage experience in the place where people live and work. It is the perfect measurement equipment that aids the LED industry and customers greatly. The 3.5-inch colored touch screen and simple interface keep up with the times. Measuring is made easy like never before. SD card storage is an essential function that proves itself useful after one does environmental measurements for the entire day. The additional Excel file and BMP file data saving selection are just wonderful for data analysis.
RPN
This app emulates the first pocket scientific calculator, offering a photo-realistic vintage experience. It simulates original operating speeds and unique arithmetic bugs, with optional modern enhancements like non-volatile registers.
- Photo-realistic look-and-feel
- Multiple vintage skins
- Vintage and Enhanced modes
- Optional key-click and key-glow
- Swipe to correct input
- Display stack and memory registers
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On January 4, 1972, Hewlett-Packard announced the HP-35, world's first scientific calculator small enough to fit in a pocket - more precisely, Bill Hewlett's shirt-pocket. The HP-35 was an immediate hit with students, engineers, and scientists. Despite its steep price of $395 (about $3000 today), it sold ten times better than anticipated in the first year. Experience this unique calculator that won HP the prestigious "IEEE Milestone in Electrical Engineering and Computing" in 2009. Features: • Photo-realistic look-and-feel • Three skins: version 1, versions 2 & 3 (1973) and final version 4 (1974) • Vintage mode and Enhanced mode • Key-click and key-glow, both optional • Swipe left across display to correct number input errors • Cut/copy/paste display value • Display stack registers and memory registers • All decimal points but one light when iPhone battery charge drops below 5% Vintage mode In this mode, peculiarities of a real HP-35 are simulated: - original speed of operation - stack register Z copied to T on trig functions - leading zeros may be entered; zero can be made negative - a negative number may be entered by pressing CHS before or after the number - a keyboard entry or RCL immediately following STO does not raise the stack - for version 1 only: simulation of a number of known arithmetic bugs Enhanced mode - non-volatile stack and registers - use registers 1 through 9 with HP-45-like register arithmetic - register 0 works as LastX register
Screenshots
Verdict
The clearest difference is price: uSpectrum MK350N at Free against RPN's $1.99. uSpectrum MK350N also leads on update cadence (every 2 months vs every 6 months) and iOS requirement (5.1.1 vs 12.0). On 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
uSpectrum MK350N is free to download; RPN costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.
uSpectrum MK350N ships an update every 2 months, RPN every 6 months. The most recent releases landed on October 26, 2026 and October 29, 2026 respectively.
| Parameter | uSpectrum MK350N | RPN |
|---|---|---|
| Price | Free — better | $1.99 |
| Rating | — | 4.4 (14 ratings) — better |
| Positive reviews | — | 71.4% of reviews |
| Number of ratings | — | 14 — better |
| Update frequency | Every 2 months — better | Every 6 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | — | Paid |
| Devices | iPhone, iPad, iPod — better | iPhone, iPod |
| Requires iOS | 5.1.1 — better | 12.0 |
| Further details — not scored | ||
| Size | 29 MB | 14 MB |
| Age rating | 4+ | 4+ |
| Developer | United Power Research Technology Corporation | CuVee Software |
In-app purchases
uSpectrum MK350N
No in-app purchases
RPN
No in-app purchases









