I'm looking for these cards for these three multimeter models: 7061; 7071; 7081.
The Solartron 7071 and 7081 have a D25 connector called Minate bus for connecting an external scanner. The bus is simply an 8 bit BCD, so it is easy to make your own scanner. There can be up to 127 channels and also a 5V 100mA supply is available, which is very handy.
The bus pinout can be found here on page 1.4.
http://www.perdrix.co.uk/Solartron7081/Solartron%207081%20User%20Manual.pdfThe bus was originally designed to control the Solartron 7010 Minate which is a 16-way 4-wire scanner from the 7075 era. The 7010 was made of hermetic reed tubes operated by electric magnets on the opposite side of the printed circuit board. That provided low leakage and very long life. I still have two units left, but the 7010 seems to be very rare nowadays. I couldn't even find a photo online.
The 7061 was designed as a system voltmeter and had an option for a built in scanner card as already mentioned.
As far as I remember the original 7061 scanner card was not very good and limited to only 8 inputs. That is why I designed a set of 32-way scanners using a DIN41612 multipole connector for the inputs (best known from Euro card format and provides up to 96 pins of decent quality gold plated contacs in a small space). The connector idea was probably stolen from the Prema scanner multimeters.
The trick was that, even though mechanically different, the 7061 also has a Minate bus. It can found in a DIP IC socket on the main PCB. The socket accepts a DIP flat cable connector which was back then more common than the current IDC connectors.
With a DIP to D25 cable it was even possible to control the 7010 scanner directly.