Comparison

uSpectrum PAR vs VPD Chart

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

Head to head
About

uSpectrum PAR

This application connects wirelessly to a handheld spectral PAR meter, allowing remote analysis and configuration of light sources. It displays detailed spectral data, light source information, and absorption metrics, with options to save and share measurements.

Highlights
  • Wireless Bluetooth connection
  • Remote light source analysis
  • Save captured data
  • Display spectrum and CIE diagrams
  • View light source metrics (LUX, CCT, CRI)
  • Share measured data via email
Features
Read full description

uSpectrum PAR is a wireless controller application for UPRtek handheld Spectral PAR Meter which provides 6 main features, namely Basic, Spectrum, PPFD Spectrum, CIE1931, CIE1976, and, CRI. Supported Devices ・PG200N (≧ FW Ver.1.1.0.B25) # uSpectrum PAR will continuously add more supported devices in the future. Connect to Handheld Spectral PAR Meter via Bluetooth ・To remotely analyze light source target. ・To remotely configure the "Integration Mode" of device ・To save the captured data of device. More Features ・To show Spectrum, PPFD Spectrum, CIE1931, CIE1976, CRI diagram of the data(*.xls), which was generated from UPRTek handheld spectral PAR meter. ・To see more information of light source, such as LUX, CCT, CRI, x, y, λp, and λpV. ・To see more information of absorption of light source, such as PPFD, PFD, PFD-R, PFD-G, and, PFD-B. ・To share the measured data via email.

About

VPD Chart

This app calculates Vapor Pressure Deficit (VPD) using air temperature, relative humidity, and canopy temperature. It offers real-time charting, sensor integration, and educational tools to understand plant growth environments. Organize data by zones and visualize dew point areas.

Highlights
  • VPD calculation
  • Interactive VPD chart
  • Sensor integration
  • Zone organization
  • Dew point visualization
  • Grow Timeline
Features
Read full description

The app calculates VPD using air temperature, relative humidity, and canopy temperature. View real-time VPD values on an interactive chart. Connect sensors for automated readings or manually input data via intuitive sliders and text inputs. Key features: • Interactive VPD chart with manual input • Default crop types • Organize charts by assigning them to different zones • Display spots that share the same VPD value • Zoom in and out of the VPD chart with a two-finger pinch and drag to pan around • VPD Target - long-press the chart to set a target VPD value • Dew point area visualization • Grow Timeline • Sync sensor historical data by importing it from sensor's app, via cloud APIs, or bluetooth • Explore sensor history by panning and zooming Supported bluetooth devices: • AC Infinity Cloudcom B2, A2, B1 • SensorPush: HT1, HT.w, HT.xw • Govee: H5051, H5072, H5074, H5075, H5100, H5101, H5102, H5103, H5104, H5105, H5174, H5177, H5179 • SwitchBot: Meter, Plus, Indoor Outdoor • Ruuvi: RuuviTag and RuuviTag Pro • Inkbird: IBS-TH1, IBS-TH1 Plus, IBS-TH2, IBS-TH2 Plus • ThermoPro: TP351, TP357, TP358, TP359 • VIVOSUN AeroLab THB1S • Shelly BLU H&T • Xiaomi Mijia 2 (LYWSD03MMC) (original and pvvx firmware) Supported devices with API connectivity: • Govee • Pulse • UbiBot • Ecowitt • Tuya • SensorPush Educational benefits: • Interactive Learning: Explore the dynamics of VPD based on changes in temperature and relative humidity by manipulating input sliders and animating the chart • Canopy - Air Temperature Link: Easily visualize and set values by linking canopy temperature to air temperature • Chart Bands Control: Toggle chart bands on/off (dew, under transpiration, prop, veg, flower, over transpiration) for a comprehensive understanding Included: 1 chart with manual input and grow timeline, device data sync & explore, default crops VPD Chart Plus subscription unlocks: • Unlimited charts • Automated VPD calculation by using sensors as the input data source • Background monitoring and Alerts (temperature, RH, VPD) • VPD history timeline, available on sensor-driven VPD charts • Custom crops Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

uSpectrum PAR4 screens
VPD Chart4 screens

Verdict

The call

The clearest difference is rating: VPD Chart at 4.5 against uSpectrum PAR's 1.0. VPD Chart also leads on update cadence (every 3 weeks vs every 8 months) and ratings volume (30 vs 2). uSpectrum PAR's advantage is in-app purchases (none vs 2) and iOS requirement (9.0 vs 15.1). On price, 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. VPD Chart sells 2 in-app purchases, starting at $3.99 per month. uSpectrum PAR asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

VPD Chart holds the better App Store score, 4.5 against 1.0. That said, the two scores are not equally well evidenced: VPD Chart has 30 ratings behind it against 2, so its average is the more settled of the two.

UpkeepUpdate frequency

uSpectrum PAR ships an update every 8 months, VPD Chart every 3 weeks. The most recent releases landed on September 16, 2026 and October 9, 2026 respectively.

Scorecard6 real differences · 4 level
uSpectrum PAR versus VPD Chart: the parameters behind the verdict, then further details
ParameteruSpectrum PARVPD Chart
PriceFreeFree
Rating1.0 (2 ratings)4.5 (30 ratings) — better
Positive reviews—73.7% of reviews
Number of ratings230 — better
Update frequencyEvery 8 monthsEvery 3 weeks — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS9.0 — better15.1
Further details — not scored
Size25 MB49 MB
Age rating4+4+
DeveloperUnited Power Research Technology CorporationINNOVO DEV S.R.L.

Customer experience

uSpectrum PAR

All ratings2 ratings
Positive0.0%
Neutral0.0%
Negative100.0%

VPD Chart

All ratings30 ratings
Positive86.7%
Neutral3.3%
Negative10.0%
Written reviews19 reviews
Positive73.7%
Neutral0.0%
Negative26.3%

In-app purchases

None

uSpectrum PAR

No in-app purchases

2 purchases

VPD Chart

Subscriptions2
  • VPD Chart Plus (monthly)3 Days trial$3.991 Month
  • VPD Chart Plus (annual)3 Days trial$29.991 Year

Questions

Is uSpectrum PAR free?
uSpectrum PAR is free to download, with no in-app purchases.
Is VPD Chart free?
VPD Chart is free to download, with in-app purchases available.
Which has better reviews, uSpectrum PAR or VPD Chart?
VPD Chart is rated higher. uSpectrum PAR averages 1.0 out of 5 from 2 ratings, while VPD Chart averages 4.5 from 30 ratings.
Do uSpectrum PAR or VPD Chart have ads?
Neither uSpectrum PAR nor VPD Chart shows ads.
Which is updated more often, uSpectrum PAR or VPD Chart?
uSpectrum PAR ships an update every 8 months, and VPD Chart every 3 weeks. Most recently, uSpectrum PAR was updated on September 16, 2026 and VPD Chart on October 9, 2026.

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