[volt-nuts] Finally got around to modifying my Fluke 845ab with LED's

[Pete Lancashire]

Some like the qrp12 peak around 610 nm.

Anyone know who made the sensor ?




On Tue, Sep 9, 2014 at 1:42 PM, Chuck Harris <cfharris at erols.com> wrote:

> Hi Dallas,
>
> The thing is, CdS cells peak sharply at about 560nm, which is green/yellow.
> They are blind to most of white light... especially to the blues which are
> prominent in white LED's.
>
> White LED's are designed purely for bulk illumination.  They have a very
> slow response so that they won't flicker when used for domestic lighting
> off of a 50/60Hz power source.
>
> There are also green yellow and red LED's that are designed the same way,
> but there are many that switch quickly too.
>
> -Chuck Harris
>
> Dallas Smith wrote:
>
>>
>>
>>
>> Hi Chuck,
>>
>>
>> Its only 84Hz, It had the offset
>> problem long before I made this mod. The new meter at work many decades
>> ago
>> also had this problem.
>>
>>
>> I pick white so the full spectrum would
>> be covered by the Csd's. Checked waveforms with scope, has sharp rising
>> and
>> falling edges. This mod may not be as elegant as a Linear Devices copper
>> mod,
>> but at lest I will not have to mess with the shielded front end.
>>
>>
>> The
>> offset may be due to the bias current in the front end reacting with the
>> different
>> polarities.
>>
>>
>> Dallas
>>
> _______________________________________________
> volt-nuts mailing list -- volt-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/volt-nuts
> and follow the instructions there.
>