[Alt-photo] 365 nm. UV-Densitometer. part 6 of 7

[Erich Camerling]

The DVM.

For reading the optical density ( D ) you can use a digital volt meter ( 
DVM )
One of the most luxury DVM's is the Lascar DPM 300 , a  4.5 digit single 
rail
backlit voltmeter.
At www.rs-online.nl   ,  search for  nr 260--038    you can see the data.
Price : EUR 172.=  incl VAT !!   For me much too expensive !
So I used a much cheaper DVM ( data : input R = 100 M ohm
accuracy =  0.1%   ± 1 digit
range = 2000 counts
resolution = 0.1 mV )
power supply = 9 -12 V
that was in my "old stuff" box. Now I can measure from D = 0.10 to 3.50
But  I could lent a Voltcraft VC 175 DMM (autorange) with 4000 counts 
and with
that meter I could measure from D = 0.100 to 3.500.
Price : EUR 33.=  incl.VAT    look at www.conrad.nl and search nr: 
124457-89.
for an example.Because of its size is will be very difficult to build in 
this meter
but you can use it for a lot of other measurements when you connect
the meter with a cord  to the densitometer. For the accuracy you don't need
the VC 175 because the delta D = ± 0.02 for the densitometer.

To be continued this week