16 Dec
2008
16 Dec
'08
1:58 a.m.
On Mon, 15 Dec 2008, Tony Duell wrote:
How did they work? I rmember seeing (and alas failing
to obtain) an
partically mechanical digital voltmeter. The circuitry was a servo
We have an old DVM from 1960, a Solartron LM 902. It has a few tubes, a
lot of Germanium transistors and also a lot of relais for the display. The
display consists of four digits, which are big black blocks with twelve
light bulbs in a 3x4 matrix (ten digits, decimal point and red background
illumination for *positive* numbers) and a mask for each digit. The light
passing the mask is then projected onto the front of the digit unit.
And best of all, this DVM contains a Weston element which still has its
nominal value.
We also have the successor from Solartron, the LM 1440. It has big nixie
tubes instead of the digit units.
Christian