hkBattousai
Advanced Member level 4
**broken link removed**
I want to design a circuit as in the picture.
I want to sence a voltage signal (x(t)) which can vary from 0V to 5000V. The signal will be driven to a MCU unit whose maximum input voltage can be 5V. I want to divide this input voltage using voltage dividers if the voltage level is greater than 5V.
Only one of the switches will contact at a time.
But to this, I need four switching elements for switching on and off these four voltage dividers. To keep the sensitivity of the circuit high, these switching elements must have as low voltage drop as possible on them. In the schematic above, I placed four FET transistors for this purpose, but I'm not sure if I made the correct choice. As you guess, the swithcing element will work only in cut-off and saturation modes. FETs have lower internal impedence that BJTs, so they are more convenient for my project, isn't it? Is there any other semiconductor element you can suggest, which would have less voltage drop on it? I think old mechanical relays are best for this, but their response time is longer, they keep more space on the board, and I don't want any non-solid-state circuit elements on my circuit.
Have any ideas or suggestions?
I want to design a circuit as in the picture.
I want to sence a voltage signal (x(t)) which can vary from 0V to 5000V. The signal will be driven to a MCU unit whose maximum input voltage can be 5V. I want to divide this input voltage using voltage dividers if the voltage level is greater than 5V.
Only one of the switches will contact at a time.
Code:
if (0V < |x(t)| < 5V) ==> take it directly to the MCU
if (5V < |x(t)| < 50V) ==> divide it by 10, then take to MCU
if (50V < |x(t)| < 500V) ==> divide it by 100, then take to MCU
if (500V < |x(t)| < 5000V) ==> divide it by 1000, then take to MCU
But to this, I need four switching elements for switching on and off these four voltage dividers. To keep the sensitivity of the circuit high, these switching elements must have as low voltage drop as possible on them. In the schematic above, I placed four FET transistors for this purpose, but I'm not sure if I made the correct choice. As you guess, the swithcing element will work only in cut-off and saturation modes. FETs have lower internal impedence that BJTs, so they are more convenient for my project, isn't it? Is there any other semiconductor element you can suggest, which would have less voltage drop on it? I think old mechanical relays are best for this, but their response time is longer, they keep more space on the board, and I don't want any non-solid-state circuit elements on my circuit.
Have any ideas or suggestions?