Humidity meter

Re: Humidity meter

Bill Tindall, E.Tn.

I bought some over the years that at best do not agree with one another by +/- 10% RH or more. Let us know if you are successful.

Re: Humidity meter

walta

The accurate way I have found is to take the wet bulb and dry bulb temperatures and look up the relative humidity on a chart.

When I get a new digital gage I do this dance and note how far off that gage is generally more than 10% some high some low.

Walta

What kind of accuracy do you need? *LINK*

Dick Coers

Here's 2 ways to calibrate.


https://www.youtube.com/watch?v=B2MmCRZ4cD0

Re: What kind of accuracy do you need?

Jerry Gibbs

Thanks. Fascinating. Will try.

After All

Mark Mandell - Gone Round In New Jersey

it's all relative, right?

Re: After All

Curt Putnam

It is only because of the temperature.

Re: Humidity meter

John K Jordan

>>>Looking for an accurate way to check relative humidity.

What is your application? How much precision do you need? How much do you want to spend?

I incubate peafowl and guinea fowl eggs and relative humidity is very important for success, especially with peafowl eggs. The cabinets have humidifiers but I have to manually control them to get the desired humidity. Each cabinet contains both a built-in digital humidity meter of unknown calibration plus a wet and dry bulb humidity capability (as described below) which is potentially more accurate than was but required using a lookup table which was a pain. The direct reading digital meters are much more convenient but my problem was, like yours, how to have confidence in the readings.

To verify, I purchased multiple digital hygrometers to put in the incubator and hatcher cabinets. They are quite inexpensive - most of what I use are Habor brand from Amazon. I initially put them all in a stabilized cabinet and compared the values and let the "vote" show which were consistent. Then I used the salt method to check to see if they were accurate. (google tells all) Then I calibrated the cabinet humidity meters and noted the reading offset needed on each digital meter. Accuracy then assumes linearity sensor but should be quite close when near the calibrated value.

Some sensors are more accurate in a specific range, so if for some reason you need to measure range far outside of the 75% value verified by the salt test, you might use a sling psychrometer. This uses two thermometers, one with a wet bulb and one with a dry bulb. The accuracy of these depends on the accuracy and precision of the thermometers. First establish a stabilized humidity in an enclosed space to close to what you want to verify. "Sling" the psychrometer through the air then quickly record the wet bulb temperature then the dry bulb and look up the relative humidity on a chart. You can buy or make one for the cost of two precision thermometers or two less expensive thermometers that have matching readings, the accuracy verified with a precision thermometer.

I made one 40 years ago with cords about 3' long. (This requires a big space and care to avoid damaging it or something in the room!)

To measure temperature/humidity in an enclosed chamber without a viewing window, a meter with a probe on a short cable is better. Opening the chamber to read the meter works well for temperature but not for humidity - the readings can drop very quickly. I use digital meters with probes in an egg cooler which keeps fertilized eggs in the best condition while accumulating enough for an incubation batch.

On my wishlist is a high quality professional humidity meter to quickly check other meters. I can't justify the top of the line but a bit of research indicates one like this might be perfect for my use: https://www.amazon.com/Amprobe-THWD-5-Temperature-Relative-Humidity/dp/B0029XL7H6

JKJ