16 Dec
2008
16 Dec
'08
11:13 a.m.
On Mon, 15 Dec 2008, Tony Duell wrote:
Solartron instruments are, not suprisingly, fairly common in England. I
have an LM1420.2 (the .2 meaning it's got the BCD output socket on the
back), which is all discrete transistors with nixie tubes for the
display. And a somewhat better model (LM1602???) which uses DTL chips.
The former certainly contains a Seston Standard Cell, I suspect the
latter does too (ass, incidentally, does that Blackburn valved DVM I
mentioned in another message).
Solartron also made soemthing called a DTU -- Data Transfer Unit. I have
a couple. A rack of boards stuffed with DTL chips, it connets to a DVM
(or counter) and turns it into a data logger. There's a relay-based
multiplexer to seelct different inputs, a real time clock board (it uses
the mains as it frequerncy refernce) and various optional output oards to
drive an IBM typeriter or card punch, an ASR33 or a Facit 4070 tape
punch. You set it up with internal links and front panel controls, and
then every so often (set by the clock PCB), it springs into life, samples
the appropraite number of inputs, takes the value from the DVM and
prints/punches it.
This instruemtn dates from the time that computers were begining to be
availale in large-ish companies, but it was not common to find them in
the labs. But with a DTU at least you didn't have to write down the
readins and later punch them by hand.
-tony
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.