Safe hygrometers

[Scott S]

I have 2 hygrometers installed in my safe one is a Lockdown Vault Hygrometer the other is a ThermoPro TP50 Digital Hygrometer Indoor Thermometer. The last one I listed shows 45% the first one I listed shows 50% humidity. Which one am I supposed to go by. Obviously one is off?
I got them both off Amazon. I'm sure you can pull them up. Which one am I supposed to go by..
Thank you

 

[Blueshound]

They aren't precision instruments. The difference between them is well within the margin of error for hygrometers (unless using sling type). Consider yourself lucky they are even that close.

 

[Scott S]

They aren't precision instruments. The difference between them is well within the margin of error for hygrometers (unless using sling type). Consider yourself lucky they are even that close.

It would still be nice to be nice to have a reliable one

 

[Mainia]

I use a couple of Thermo Pro TP357 in my daughter's 3D printing business to monitor our filament bins when the desiccant packs need microwaving. Here is my question, why are they so off? I can assume price point sensor cost would be the answer. Can you buy an "accurate" one under $75--$100? I would think by now someone would make an accurate sensor other then for high end lab equipment, but I may be wrong. If you go by these units on the low end, with the + or - you have a chance of being 18-20%+ off, which is kind of too far to deviate in many applications.

 

[Mainia]

I have 2 hygrometers installed in my safe one is a Lockdown Vault Hygrometer the other is a ThermoPro TP50 Digital Hygrometer Indoor Thermometer. The last one I listed shows 45% the first one I listed shows 50% humidity. Which one am I supposed to go by. Obviously one is off?
I got them both off Amazon. I'm sure you can pull them up. Which one am I supposed to go by..
Thank you

Obviously both COULD be way off in the case of consumer grade hygrometers it seems.

 

[Mainia]

Ok, I found one.

Labconco Moisture Monitor/Hygrometer - Humidity and Hygrometry, Hygrometers

For placement inside the glove box main chamber to continuously monitor moisture levels

www.fishersci.com

It takes a $330 unit to get a +/- 2 mid range to a +/- 4 in an end range. Which is where I would deem acceptable for use case. BUT the style of this unit is not conducive to some peoples application. I guess this unit could be used to put some form of +/- on each of your cheaper units with a Sharpie pen, since you could be in a narrow window where you want to read with a cheap unit.

Fisherbrand Traceable Humidity Meter - Humidity and Hygrometry, Hygrometers

Retains highest and lowest readings recorded over selected period

www.fishersci.com

 

[SC Maintenance]

The element of a high accuracy thin film humidity sensor itself is very expensive to produce. Here is one around $500 bucks for a 4-20mA sensor itself - no display or controller. https://www.veris.com/995829/product/veris-hp2xmsx-pendant-humidity-sensor

Most consumer applications - ie whats the humidity in my basement - are fine with +/-5%.

As to which of yours is more "correct" - it likely depends on the actual humidity range - as likely neither are linearized or trimmed.

You can get better, get out your check book.

 

[Scott S]

How about something a little bit more affordable, does anybody use anything that's a little bit more affordable, that maybe accurate? Just curious. It's not like it's being, put in a basement, or garage, it's in a Bedroom.

 

[SC Maintenance]

How about something a little bit more affordable, does anybody use anything that's a little bit more affordable, that maybe accurate? Just curious. It's not like it's being, put in a basement, or garage, it's in a Bedroom.

Thats what I am saying. The actual sensor element in these things are made by applying a hydroscopic material on a glass plate and sealing it with a polymer or similar - then the resistance or capacitance or something or other changes relative to how much moisture it has absorbed.

Making a precise and more importantly a repeatable and linear one is expensive - it has to be perfect thickness and applied evenly and possibly even trimmed and calibrated.

If you find a Chines one for 12 bucks that says its +/-2% - there lying to you.

 

[Scott S]

Well I checked the digital hygrometer from Thermopro it came up at 74% instead of 75% in the salt test, After 24 hours. That's close enough for me.

 

[two-up]

I use both of these:

Extech 445815

EXTECH Instruments and Test Equipment | an Industrial Electronics, Inc Company, Distributor for Extech Instruments and Accessories

Extech-online.com is a premier distributor of Extech Instruments, providing tools for solutions to predictive maintenance, electrical testing, thermal imaging, thermography and plant maintenance requirements

www.extech-online.com

Temp Stick

Temp Stick

Temp Stick™ All-In-One WiFi Temperature & Humidity Sensor with 24/7 Monitoring and Instant Alerts. No monthly fees. Free same day shipping. Made in USA.

www.tempstick.com

The Extech can be had for about $88.00usd Amazon and the Temp Stick is about $130.00 usd or so last time I checked

The disadvantage to the Extech is that you will have to drill a hole or use the electrical access if your safe has one-I don't know if an extended sensor is available.

The Stick makes more sense as we can use it to monitor our house temp when we must go away during the winter. The app to check the temp and history is free and quite good, somehow the signal always gets out of the safe, go figure.

One or both are traceable-forgot the details-battery life is about even at about 2 maybe 3 months and -WE- have found that the inside data is very very close to the ambient data.