Analog vs digital

[OldGob]

I have three hydromometers.  The two analog ones came with their humidors and the digital I bought.  I calabrated all three using the salt test and by using the Boveda calibration kit.  One analog is two points low and the other is three points low.  Oddly, the digital is five points low.  I know digital are supposed to be more accurate but in my case it is not.  Unusual?

 

[BlindedByScience]

What I've seen is the difference between consistency and accuracy.  Your digital will probably be consistently 5 points low, so it's pretty simple to compensate for.  The analog hygro's will typically be all over the map.
 
Depending on digital, some have a 'cal' control somewhere to tighten up the offset.  Some, but not all.

 

[OldGob]

I hadn't thought about the consistency issue and have not checked that.  Thanks for that info.

 

[Devil Doc]

Should have got an adjustable digital. Dial in the error and you're all set 'til the next battery change.
 
Doc

 

[BlindedByScience]

As long as we're on the subject, the salt test is good, but I really recommend conducting the test in a mason jar or old mayo jar or something with a tight, screw on lid.  You'll get far more consistent and repeatable results that way.  Even double bagged in ziplocks, the jar wins hands down every time.
 
Lastly, the little cal kits that Bovida has are really good and probably worth the money.  Eight bucks on Amazon with free shipping.  Comes with a proven humidity source and a bag that seals perfectly.  Not hard to recommend:
 
http://www.amazon.com/Boveda-One-Step-Hygrometer-Calibration-Kit/dp/B000A3UBLA/