In order to minimize the number of components for measuring different types of signals(Resistance, Voltage, Current, ETC), I have designed circuit using DIP switch which the user can turn on and off depending on the usage.

However, I want to use a MCU to control the switches. Can I use analog switch instead and would circuit behave the same? For example, linearity, noise performance, and etc...

You can assume that the switch resistance won't affect the circuit. We have prevented that by design.

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    \$\begingroup\$ You'll probably need to add more details (preferably a schematic) of that section of your circuit to get a good answer. Apart from resistance there can be other issues related to capacitance and voltage / current ratings. \$\endgroup\$ – PeterJ May 31 '14 at 3:41
  • \$\begingroup\$ You say switch resistance won't affect the circuit but then mention noise and linearity. It's guaranteed those will be worse with an analog switch. Enough to matter? Kind of a mystery without a lot more information. \$\endgroup\$ – Spehro Pefhany May 31 '14 at 3:45
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    \$\begingroup\$ The pros use relays. \$\endgroup\$ – Ignacio Vazquez-Abrams May 31 '14 at 4:15
  • \$\begingroup\$ @PeterJ The analog signal we want to measure will be band limited(by LPF) to less than 10 Hz. The current through each of the switch will be 1mA at max. \$\endgroup\$ – Steve May 31 '14 at 7:14
  • \$\begingroup\$ @SpehroPefhany I think I will have try both of them and compare \$\endgroup\$ – Steve May 31 '14 at 7:16

Here are a few guidelines for choosing an analogue switch

  • Analogue switches usually only switch signals that have peak voltages inside the power rails of the switch. Some will allow higher/lower voltages to be switched - read the data sheet.
  • The current should be limited - read the data sheet
  • The on resistance needs to be factored in to see what errors may result
  • On-resistance linearity may also be a factor that could distort the signal - read the data sheet.
  • Switching speed doesn't sound like a problem on this application
  • Cross talk is never zero but is unlikely to be a problem at below 10 Hz but take note that when the switches are operated there will be some charge injection from the control side of switch into the analogue side.

Good luck, it's doable with analogue switches by the sounds of it.


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