Piano World Home Page Forums Our Most Popular Forums Piano Forum Piano Life Saver - Data Showing What It Does

Hi Retsacnal,

Yes - the temps in the house when I get up are usually in the mid-upper 50s. ON very cold nights, it's gotten as low as 49 in the house - but that's once or twice in the winter (I realize reading this that it sounds crazy, but we sleep better in a cool house, under warm comforters). During the day, we bring the house to 68-70, and keep it there until we go to bed and turn the heat off.

Thanks for linking the graph in.

Steve

Seeker, your PLS reference humidity seems to be 10% off. My previous one maintained steady 40%, and new one 45%, so there are variations. You might want to have it recalibrated.

@Twindad - I remembered that there had been numerous discussions about the PLS previously, but I was too lazy to look them all up - hence - starting this new data driven thread. Looking at the description of the Tempo Disc, it looks to be more accurate than the Govee, so I will order one. Thanks for the lead.

@kre - Thank you for the data on the setpoint for relative humidity for the PLS. I've just emailed the manufacturer including the screen shot that I included to start this thread along with the questions: 1) what is the set-point for relative humidity, 2) is it possible for an end user (technician or not) to re-set it, 3) if not, aside from replacing the control unit, should I replace the "smart bar". I will post the answer I get.

And, yes, I did believe, and continue to believe, this is a discussion worth having. Looks like we'll get some real data soon on the effectiveness of the PLS on a grand piano from @Twindad. I will join him and put a sensor into the Konzert8 as well as next to it after calibrating one to the other (or as close as possible depending on the calibration ranges possible) and let them roll for a week. Should be interesting since we're going to be going through weather changes here as we emerge from weeks of deep-freeze temps unusual in the Mid-Atlantic coastal area.

I think PLS used hair hygrometer in the past that probably have some set screw for bias adjustment (though not for user). If they still use same tech, well that just SCREAMS chinese competition to come out with system having modern sensors without bias wandering all over the place. Heck, I could build brains for the system myself as a hobby project using raspberry board.

For those who haven't read the other posts on this subject, that competition is already here and the best one I know about is the Inkbird controller. I'd suggest just using that instead of having to send off the PLS controller for calibration or replacement.

Having done extensive research about 8 years ago on RH measurement instruments, I can tell you that, at that time, most inexpensive RH electronic sensors were notoriously inaccurate. Passive mechanical analogue ones were, and are, much better. I still use multiple $10 mechanical hygrometers that are within 2% of each other and I measured them using a saturated sodium chloride solution test vessel. I bought 10 of them at Canadian Tire, measured them all, and returned the 7 that failed.

Electronic sensors, even those costing hundreds of dollars, still fall into the +/- 3 to 4% calibration standard. This means two devices are considered calibrated to the standard if one reads 47% and the other 53%.

The accuracy of the electronic temperature sensor, which is used to compute the RH% is critical. A one degree Celsius error can cause an RH error of over 3% on top of the inaccuracy of the RH% sensor.

But, for a commercial logger, this measurement is usually achieved by taking a measurement over a set time period. There is an assumption that the temperature sensor and the RH% sensor are stabilized at the end of the measurement period. If the temperature or RH is changing rapidly, for example, the forced air heat just came on in the room. The sensors may not have reached a stable point and the measurement will not read the final value. This adds another level of inaccuracy to the measurement.

I designed and built two psychrometers, one mechanical, and one electronic, fan blown version still using an evaporative wick over a thermistor. The hand operated sling psychrometer was much more accurate than my home-made electronic device as well. My wife put a stop to slinging it near the grand piano however.

Electronic sensors age rapidly and are sensitive to many airborne chemical residues -delrin, acetate, PVC, polystyrene, adhesive tapes and some adhesives. The response time increases with age as well. Recalibration or replacement of the RH sensor is measured in months to a year for critical applications.

Horse hair hygrometer is still the most accurate and reliable over long time periods.

Is this the one you installed?

https://inkbird.com/products/ihc-200?_pos=3&_sid=23e366188&_ss=r

Could you post a picture of how you installed the Inkbird?
Connection seems simple enough: SmartBar -> Humidifier On outlet, Dehumidifier Bars -> the other outlet.
Hang the sensor (with a cable tie?) under the sound board in a central location

Looking at the Inkbird manual, one gets to set a RH value, and a humidification and dehumidification value. May we know what your settings are?

Also, regarding accuracy, the advertising copy read ± 3% for that particular Inkbird. This would be better than ± 7% in the Damp-Chaser sytem. See section immediately following for where I got the DC number.
=====================================
Regarding calibration - I wrote Damp-Chaser Corporation to ask if I needed to recalibrate or replace my control unit. I sent the same screen shot that I posted here. Shane Owenby, RPT, responding for them said, "Thank you for contacting us. It would appear from your graph the system is working well within your piano. Our switch calibrations have a differential of ± 7% range and and yours is functioning well within that. If the piano pitch is stable and the system is keeping it within an acceptable range, which it appears to be, then no calibration is needed. FYI, readings taken by many hygrometers are ± 10% or more out of the box depending on manufacturer and model. It does not appear that any replacement of the Piano Life Saver system or its parts are necessary".
=========================================
The pitch on both my pianos is stable, particularly given the multiple hours a day, 6 days a week use, they get. There is a drop to about 439.2 Hz a month into the coldest part of winter, and a rise to about 440.7 in late July and August - but the rises and falls are uniform across the full compass of the keyboard, i.e., the instrument stays in tune with itself though at a slightly higher or lower set-point.
=======================================
I am appreciating this discussion a lot. Thanks to all who have contributed.

Interestingly, my original PLS controller was also pretty consistently keeping the humidity at about 32% RH, according to my sensor. It was keeping it stable, so I didn't worry too much, but given the overall more humid environment here, was wondering if setting it at 40-45% would mean less work for it to do (and less discrepancy between the ambient RH and the soundboard environment).

On the advice of my tech, I ordered a Willhi humidity controller

He said he had some colleagues at a university in Virginia using and testing them with great results. I've installed it, and set it to 43-on / 42-off. The graph in my earlier post is with this controller; so far it's working well according to these readings. The nice thing about an easily programmable controller like this (as opposed to the PLS controller) is that you can set it at say, 35% in drier winter months, and 45% in humid summer months (in other locations, not here in the bay area).

I don't know if the Willhi is better or worse than the Inkbird - just offering up different options.

@seeker: That's the one :-)

Mine is installed in an upright not a grand but the installation it was very easy. All I did was to hang the controller on a hook inside the piano then drill a hole in the base and lead out the power cord to my mains supply. Inside the piano you then just plug all your installed humidification device(s) to one control socket and your de-humidification device(s) into the other. I don't need a humidifier myself and so have just Dampchaser rods and a very small 'Peltier' type dehumidifier plugged into the control socket. Do give some thought to where the sensor is positioned as r/h will vary from place to place within a piano with DC units fitted and in particular you don't want to measure the air directly above the rods or in the 'exhaust' stream from the humidifier. To state the obvious you also don't want the plastic controller case touching the DC heater rods, it is a robust high quality plastic but ....

My particular controller was very accurate (2%) when I measured it and it can be calibrated if required. That said the absolute accuracy of the calibration doesn't really matter that much- if you know it is out by say 8% RH reading you can just allow for that in your settings but I do like to have mine displaying accurately. (This is assuming that your controller lets you set the desired humidity in the first place so that you can allow for the inaccuracy, if it is factory preset and not adjustable then you are at the mercy of what the manufacturer thinks is a good and sensible RH to aim at in your climate and the accuracy to which the sensor has been calibrated). What you also don't want to have is a crappy sensor that drifts with time or is very non-linear i.e. one that is only accurate at the RH you calibrate it at.

I like the accuracy of the Inkbird and the display it offers for reassurance. I like that I can set it to maintain whichever humidity level I want. I like that I can set the RH at which it starts working and the RH that it switches off. I like it's (apparent) physical robustness. I like that I can control both in-piano dehumidifiers and my choice of external room based humidifiers from it. I like many things about it :-)

The only thing I would like extra would be the ability to profile it across the measurement range rather than just calibrate at one RH point and rely on the sensor's linearity for other values but, AFAIK, there isn't anything like that commercially available.

Ah, you also asked about the settings I use. I use an independent external de-humidifier in the room to maintain 50% humidity (this works out at about 53% due to the inaccuracy of it's humidstat which I can't calibrate) and I have the Inkbird controlling the internal DC rod and mini-dehumidifier with a target of 55%. It is seldom necessary in my climate to do any humidification (other than what my plants provide) but if/when it is I have a Venta airwasher available to plug in. I have left the Inkbird hysteresis band settings at default but you could alter that to maintain a narrower control range if you want. Even though the room based dehumidifier is set to a lower R/h target than the Inkbird it is surprising how often the internal units are activated - I think that is because they maintain a finer band and are more reactive (i.e. after achieving the r/h target and switching off they will remeasure and if necessary switch back on in a much shorter cycle). I do need the external unit as the DC rod alone is unable to maintain my target r/h once the external r/h is more than about 65%.

I think there has been some development with cheap RH sensors in recent years. I have 3 Govee sensors and 1 other brand RH sensor, and they read identical figures within 1-2%. I threw my hair hygrometer to trash bin years ago.

Some years ago on PW a technician posted a picture of his horse hair hygrometer he used in his shop. The hair was about 2 metres in length mounted on a much larger board with a scale he had marked on it. The 1% divisions were centimetres apart.

It is likely as you say that sensors have improved. I was quoting today from a white paper published in 2012.

In the grand scheme of things, a slow variation of RH over a large range is not likely to harm the piano, aside from excessive humidity causing rust and/or mould and extreme dryness that cracks the soundboard.

For me, the only advantage of a tight tolerance is the ease of maintaining a standard pitch for recording, editing and chamber music players.

PLS turns on at 35% / off at 55%, meaning 20% difference. I would be simply amazed that sensor can even measure 1% difference reliably. The time that it takes to warm up the pad, start humidifying, wait for humid air to disperse below soundboard, then read the new humidity, and cut off pad heating, even 10% cut-on/off would be extremely small. But hey, if it works, it works.

Regarding PLS answer about accuracy. They state that their system aims for 45%. Add to that 7% tolerance, and argument that room sensor can have 10% tolerance (lol), that means PLS can claim that their system maintaining any humidity from 28% to 62% is working perfectly. I wouldn't accept this.

Now that is a separate problem from the sensor and there will indeed be overshoot problems where the control system does not respond instantly. This is rather difficult to deal with but it can be done, I once modified my coffee machine to maintain a properly even temperature through the on/off heating cycles from the standard thermostat but I had to use a fuzzy logic controller that learned the overshoot characteristics of the system to do that. I really don't think we have to go that far with our pianos :-)


Severely sub-optimal is I think what we might call that. If DC did nothing more than simply use a more capable sensor it would cut down a lot on those tolerances.

Our Carrier HVAC system, 12 years old, uses fuzzy logic and it holds 71F (21.667C) precisely, once at that temperature. The logic controller learns how long it takes to arrive at that temperature from the night set-back, depending on the time of year and outside temperature average and current rate of change. Doing so allows it to have the temperature where we want it at a given time in the morning.

Funny thing though. The hysteresis is based on the integer value of the temp which I find weird, and, when I had the data read in Celsius, it would vary the set temp of 21C from 20C to 22C, and we could really feel the temp change. When I changed it to Fahrenheit, the display locked in at 71F and we experience no apparent hysteresis (obviously there is). I think the two level burner (natural gas) and DC variable speed motor and pressure sensors keep the system at optimal efficiency. It was born in the USA and I guess can't think in SI.

Very nice - that goes way beyond my coffee machine. Mine just learned the overshoot from its switch on/off dynamically and modified its behavior
accordingly. I could give weights for the last action, average for the week and average for the month for how it decided to behave but it had no external references or calender data store. There again the controller only cost me around $20 and it made nice coffee :-)

Coffee, the elixir of life...until dinner.

OK, I promise this is the last thing I'll say about coffee as there are separate fora dedicated to that and folks here might be getting bored. The irony is that, just as you like the mechanical methods of measuring rh, and my profession being computers, I'm also an analogue man at heart and my current upgraded coffee maker is a big brass spring and lever job using a pressure-stat rather than thermostat for increased sensitivity and then instead of fuxzzy logic I have an E45 groupset that essentially cocoons the coffee chamber in almost 45Kg of brass. That amount of hot metal keeps the coffee at a constant temperature through the brew far better than the fuzzy logic controller could.

In similar manner I think the PLS system might do the job better than we think. We would like a sensor that was accurate and didn't wander and sort of kept a humidity constant within 5% or so rather than 40% but does it really matter? Even if the PLS maintained rh does swing over a potential 40% or so, provided it is on a short control cycle and sweeps through that range in just a few minutes before repeating the piano won't have absorbed or lost any significant moisture in that 10 minutes so it probably doesn't matter. Doesn't matter as long as the average humidity for each cycle is maintained that is , if the sensor drifts badly and the average r/h wanders all over the place we are stuffed.

So. I think you prefer espresso. A man after my own heart.

Cheers