[Heathkit] IM-17 Question

[Garey Barrell]

Dennis -

What's special about a mercury cell is that it's output voltage remains 
extremely constant at 1.35V over about 95% of it's life.  Unfortunately 
for photographers and others who needed stable battery voltages, the 
hysteria over mercury has all but eliminated mercury cells from the US.  
Just in the last week or so, someone accidently broke a MERCURY 
thermometer in their home, called 911 (!) and over 100 personnel showed 
up with hazmat suits and decontamination equipment to handle this major 
spill.

Anyway, use of another type of battery in your meter will just result in 
it being out of calibration each time you use it as the alkaline or 
other battery voltage declines over time.  The closest thing available 
now is a Silver Oxide cell, which has about a 1.5V output with a flatter 
discharge curve than an alkaline cell.  Low dropout regulators that will 
regulate with as little as 0.35V drop are available now that could maybe 
regulate from a 9V battery and hold your calibration over time as the 
battery declined.

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>



Dennis Berry wrote:
> Thanks for the reply Mike.  Others said the same thing actually.  I don't
> know what was special about the 8.4v mercury's back then.  Maybe it just
> lasted longer?
>
> I've attached a partial manual someone sent me in response.  Keep it or toss
> it as you see fit.
>
> Thanks again for the response though Mike.  Looks like this will be a handy
> addition to the shack.  Digital's are nice, but sometimes a good ole analog
> is handy.
>
> Dennis
>
>
> ----- Original Message ----- 
> From: "Michael Tortorella" <w2iy at verizon.net>
> To: <heathkit at mailman.qth.net>; <dennisberry at worldnet.att.net>
> Sent: Sunday, January 07, 2007 16:24
> Subject: Re: [Heathkit] IM-17 Question
>
>
>   
>> Dennis,
>> I have an IM-17 and simply replaced the unavailable battery with a plain
>>     
> ol'
>   
>> 9 volt and it works just fine as is.  You may want to recalibrate.  I've
>> used this for years with no problems.
>> Sorry I don't have a manual, though.
>> 73
>> Mike W2IY
>>
>>
>>     
>> ------------------------------------------------------------------------
>>
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