Hygrometers (humidity meters) are sensitive instruments. I am old enough to have worked on air con systems that used horsehair hygrometers and humidistats to monitor and control humidity. Human hair is said to work better.  If you google “hair hygrometer” you may find more info on making your own.

As said, sensitive instruments. So hanging a a 1kg weight on your gut is probably stretching it and doing all kinds of weird stuff to it. Try it with shorter length of gut and minimal weight on it. Attach the gut, or hair, to some kind of lightweight pointer that is pivoted close to the attachment point for the gut/hair, so a small amount of movement of the gut/hair is magnified by the leverage of the long end of the pointer. You might need a small spring or weight just enough to keep tension on the gut/hair but not stretch it or stop it contracting.

Seaweed!

Hi,

Back in the 1970s I used to sometimes record the readings from various instruments in a climatological weather station in New Zealand. One of the instruments was a recording humidity meter. The sensor part of it was a bundle of horsehair about 6″ long. It may have comprised perhaps a dozen individual hairs. I’m not sure if the instrument measured a length change with humidity or if the bundle was twisted and changes in torsion were measured. Each day, the horsehair was cleaned using a small paintbrush and distilled water. Apart from removing any salt from the horsehair which could have affected its reaction to humidity, it also checked the zero of the instrument which read 100%r.h. once a day when it was cleaned.

Recording clockwork thermohygrographs turn up on the local auction site fairly regularly and don’t fetch all that much ($200 – $300).

Wall mounted analog hygrometers are also readily available.

Regards,

Alan C.

I have a gut feeling this is going know where!

They do exist, and must be fairly simple. My wife has a clock (like this one) in her Summerhouse/workshop with a subsidiary humidity dial. The battery only drives a standard quartz movement so the humidity ( and temperature) sub dial(s) are mechanical. Amazon do (at 2 for £10!) a non-battery thermometer/hygrometer using presumably similar mechanisms.

I wouldn’t be thanked for disassembling my wife’s clock, but at Amazon’s price I could be tempted to buy one and investigate how it worked.

PS this patent might be of interest.

Can’t find the book it’s in, not ‘The Amateur Scientist’, but from memory this arrangement should work after a fashion:

A drinking straw is pinned to a vertical board by a pin.  The straw is held away from the vertical surface by a glass bead (Ladies have thousands of ’em).

The weight of the roughly horizontal straw is supported by a human hair, about 150mm long, the far end connected to the fixed pin.

As the length of the hair varies with humidity, the movement at the pointer-end of the straw is amplified by the lever action about the axle pin.

Longer the hair the better, but the biggest improvement would be to make a proper lightweight gear amplifier – a clock-making job.  I vaguely remember it being recommended to slice off the pointer end of the straw to reduce weight.

By far the easiest way to measure Relative Humidity with an electronic sensor.   RH depends on temperature and pressure, so these have to be measured first.   The BME280 does both, and does most of the necessary maths.  The main correction needed outside the sensor is your local air-pressure at sea-level, which varies with the weather.  Accuracy about 4 times better than a good hair instrument.

Arduino instructions here.

Dave

On 4 June 2024 at 19:04 SillyOldDuffer Said:

Can’t find the book it’s in, not ‘The Amateur Scientist’, but from memory this arrangement should work after a fashion:

 

A drinking straw is pinned to a vertical board by a pin.  The straw is held away from the vertical surface by a glass bead (Ladies have thousands of ’em).

The weight of the roughly horizontal straw is supported by a human hair, about 150mm long, the far end connected to the fixed pin.

As the length of the hair varies with humidity, the movement at the pointer-end of the straw is amplified by the lever action about the axle pin.

Longer the hair the better, but the biggest improvement would be to make a proper lightweight gear amplifier – a clock-making job.  I vaguely remember it being recommended to slice off the pointer end of the straw to reduce weight.

By far the easiest way to measure Relative Humidity with an electronic sensor.   RH depends on temperature and pressure, so these have to be measured first.   The BME280 does both, and does most of the necessary maths.  The main correction needed outside the sensor is your local air-pressure at sea-level, which varies with the weather.  Accuracy about 4 times better than a good hair instrument.

Arduino instructions here.

Dave

Negative gravity in Somerset?

On 4 June 2024 at 22:37 duncan webster 1 Said:

On 4 June 2024 at 19:04 SillyOldDuffer Said:

Can’t find the book it’s in, not ‘The Amateur Scientist’, but from memory this arrangement should work after a fashion:

 

A drinking straw is pinned to a vertical board by a pin.  The straw is held away from the vertical surface by a glass bead (Ladies have thousands of ’em).

The weight of the roughly horizontal straw is supported by a human hair, about 150mm long, the far end connected to the fixed pin.

As the length of the hair varies with humidity, the movement at the pointer-end of the straw is amplified by the lever action about the axle pin.

Longer the hair the better, but the biggest improvement would be to make a proper lightweight gear amplifier – a clock-making job.  I vaguely remember it being recommended to slice off the pointer end of the straw to reduce weight.

By far the easiest way to measure Relative Humidity with an electronic sensor.   RH depends on temperature and pressure, so these have to be measured first.   The BME280 does both, and does most of the necessary maths.  The main correction needed outside the sensor is your local air-pressure at sea-level, which varies with the weather.  Accuracy about 4 times better than a good hair instrument.

Arduino instructions here.

Dave

Negative gravity in Somerset?

If only!   Classic example of why memory is untrustworthy.  Looks like I remembered the principle, but somehow inverted gravity,  Down here in Zummerzet we blame the Scrumpy.    If you can remember the night before you didn’t have any!

Dave