So i am using a keysight general purpose switch(spst form A) and I am trying to figure out how to change the voltage polarity since I only have a single power supply. I have this diagram that one of my friends helped me with but I am bit confused. If i close switch 1,2,4 would i be getting positive voltage? If i close 6,3,5 I get negative voltage? I guess I am just having a hard understanding what happens when i connect power to NO as opposed to COM. Any help is appreciated or any good references on understanding switches.
Figure 0. The schematic (subsequently removed) on which this answer is based.
Figure 1. A typical polarity reversal switch.
Your circuit is difficult to understand due to a poor schematic and poor labeling. It's also a bit dodgy as all the switches are independent and short circuits can be created by connecting 3 and 4, for example.
A more typical arrangement is shown in Figure 1. Here a DPDT (double-pole, double-throw) switch is used. In the position shown the top output wire will be positive. Throwing the switch reverses the polarity. Note that it is impossible to short-circuit the supply with this switch.
If i close switch 6,2,4 would i be getting positive voltage?
You only need to close 2 and 4. We'll get to 6 later.
If i close 1,3,5 I get negative voltage?
You only need to close 3 and 5. We'll get to 1 soon now.
I guess I am just having a hard understanding what happens when I connect power to NO as opposed to COM.
Figure 2. (a) The equivalent circuit for your setup. (b) A simpler way?
Switches 3 and 4 in Figure 2a show how your schematic is configured. It's a little weird, to say the least but it may have suited the PCB layout. They suffer the same problem as the others in that your 1 and 6 can both be connected simultaneously and short out the power supply.
Figure 2b shows a better way of switching the ground connection. Again, a short circuit is not possible. If an un-grounded output is required then an on-off-on type of switch (centre-off) would be required.
It's been brought to my attention that if the wrong switches are open/closed I could end up messing up my unit and DUT. How can I avoid this?
Figure 4. Revised schematic posted by OP.
This revised schematic doesn't change the fact that you have purchased the wrong switches for the job. The only thing I can suggest is that you SPST3 and SPST5 are installed in reverse orientation to 2 and 4. Then you use the following procedure to change polarity.
- Switch power off.
- Switch SPST 2, 3, 4 and 5 up for standard polarity.
- Switch SPST 2, 3, 4 and 5 down for reverse polarity.