thx for the replies everyone. soz the reed relays are taking longer to arrive from the seller than anticipated but I will recap on what my thoughts are on them from what I can tell:
Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits, the link is magnetic and mechanical.
I mentioned CMOS switching earlier, with a focus on the CD4066 quad bi-lateral switch. The problem when measuring voltages through one is the large losses. It just isn't in my opinion a good solution if you are scanning many inputs in data acquisition where accuracy is important.
I can see what you mean about relays. Being that there is no voltage drop or anything affecting the signal form the pcb's it is ideal from what I can see.
The relay component basically allows one circuit to siwtch to completely seperate circuit. There is no electrical connection inside the relay between the two circuits I want to switch between since the link connecting them inside the relay is magnetic and mechanical.
I have looked at the Output Relay Scanners and came across one which was described as a row of relays on a panel that needed to be switched in order to turn on all the lights at the start of the day and off at the end of the day.
A relay scanner allows (amongst other things) a large group of relays to be switched at the same time. Since I only need this particular feature, I can save money designing a one-off item on stripboard using:
- stripboard
- row of reed relays
- row of screw terminals as the inputs from the pcb
- row of screw terminals as the outputs from the reed relays to the momentary push buttons
- common components (resistors and so on)
From what I can see a reed relay takes up alot of real estate on the stripboard, the ones coming are the same footprint as a 16-pin chip with a 0.1" pitch between the pins but their height is triple more or less. They only seem to come in single pole changeover or double pole changeover. Will update again later.