TL;DR: I put 4 independently calibrated humidity sensors inside my VCure and found it reads about 2-3% off on humidity. Many custom recipes I see on here are ~2-3% higher than the stock recipes. Coincidence? Maybe your VCure needs calibrating too. Here's how I tested mine.

All Sensors

Cycle

https://preview.redd.it/56bj83xml4sg1.jpg?width=2019&format=pjpg&auto=webp&s=32c1e5d421bf1aa53dab59a629369bfd3d80bb27

Why I did this

I've been browsing VCure recipes on this sub and noticed a pattern: a lot of custom "dialed in" recipes have humidity values that are a few percent higher than the default recipes. People say things like "the stock recipe comes out too dry" and bump humidity up by 2-3%.

That got me thinking - what if it's not the recipe that's wrong, but the VCure's built-in sensor?

My approach: Don't trust any single sensor

I work with home automation (Home Assistant) and sensors for a living, so I decided to do this properly before even thinking about recipes.

Step 1: Get multiple reference sensors

I got 4 identical Zigbee temperature/humidity sensors - small, battery-powered units with displays that I can also read remotely. The key idea: one sensor can lie to you, four sensors tell a story.

Step 2: Calibrate in a climate chamber

This is where it gets serious. I had access to a calibrated climate chamber at work - basically a lab-grade box that holds exact temperature and humidity. I placed all 4 sensors inside and ran 3 tests at different humidity levels:

Test	Chamber Reference	Sensor Avg (raw)	Deviation
1	58.5% RH	55.3%	-3.2%
2	47.6% RH	49.8%	+2.2%
3	67.1% RH	64.3%	-2.8%

Every sensor had its own offset. Using the climate chamber as ground truth, I programmed individual correction values into each sensor (+1.5% to +4.9% depending on the unit). After correction, all 4 sensors agreed within about 1% of each other and matched the chamber reference.

Step 3: Place all 4 sensors inside the VCure

I distributed the calibrated sensors at 4 different positions inside the VCure (left to right) to also check for humidity gradients across the chamber. In Home Assistant, I set up a sensor that calculates the real-time average of all 4, plus a rolling 10-minute mean to smooth out fluctuations. This gives me one reliable number to compare against.

Step 4: The moment of truth - VCure vs. calibrated sensors

With the VCure set to 59% humidity target:

• VCure probe reading: ~58-59% (jumping between 56-61% with only 1% resolution)
• Calibrated 4-sensor average: ~61% RH
• The actual humidity inside was about 2-3% HIGHER than what the VCure displayed

Step 5: Dialing in the VCure offset

The VCure has a built-in humidity offset setting. I went step by step and monitored with my calibrated sensors:

VCure Offset	Calibrated Sensor Avg	Result
-6	~63%	Way off - wrong direction!
-4	~62%	Still too high
-2	~59.3%	Right on target

My unit needs an offset of -2 to actually deliver the humidity it claims.

The recipe connection - this is the interesting part

Think about it: if VCure units generally read low on humidity, the actual environment inside is wetter than what the display shows. So when people create custom recipes and bump humidity UP by 2-3%, they might unknowingly be compensating for a sensor offset - and ending up at roughly the humidity the original recipe actually intended.

I'm not saying every VCure has the same offset. But it would explain why so many people independently arrive at "original recipe + 2-3%" as their sweet spot.

How you can check yours (no climate chamber needed!)

You don't need lab equipment. Here's a simple approach:

1. Get a Boveda calibration kit (75% or 62%) or even just 2-3 cheap hygrometers from different brands
2. Seal them together in an airtight container and let them stabilize for a few hours
3. Compare readings - this shows you how much your sensors disagree
4. Put them inside your VCure and compare against the VCure's display
5. Adjust the VCure's humidity offset until your reference sensors confirm the target

Even a rough check is better than blindly trusting the factory calibration.

What's next for me

I don't have my own recipe yet - and that's the point. I wanted to get the measurement side right first. Now that I know my unit's actual offset and have 4 calibrated sensors continuously monitoring via Home Assistant, I can develop a recipe knowing that the numbers I set are the numbers I actually get.

I'll share my recipe journey once I have results. But for now: calibrate first, recipe second.

Has anyone else noticed this offset on their unit? Would love to hear your numbers!

Setup: VCure C80, 4x calibrated Zigbee HT sensors, Home Assistant for continuous monitoring and averaging