2 Replies Latest reply on Jun 30, 2019 4:58 AM by JaGe_4104756

    PSoC 5LP - Voltage drop messurement - overflow problem

    JaGe_4104756

      Hello and sunny greetings from Germany :-)!

      Now to the sunny part. I'm working on a voltage drop measurement in a photovoltaic circuit. My 10 laboratory cells deliver a voltage Voc = 5V and an Isc = 100mA. With a shunt resistor Rsh = 60 ohms, a resistor Rv = 100 ohms and a LED Uled = 2.5V I have a voltage range at the shunt resistor 0 mV < Ush < 927.6 mV. Over an output I let in addition the calculated current spend (max 15.45 mA).

      The following problem exists:

      1. When reading the voltage at the shunt resistor I can observe when outputting that the AD converter reaches a maximum and overflows.


      2. The AD converter operates with an input range +/- 1.024V (-Input +/- Vref) and the reference voltage internally with 1.024V


      3. As an example, I have attached the picture below.
      Here it can be seen that the voltage drop rises up to approx. 61 mV (= 1mA), then overflows and the values are counted up again starting from 0 mV. So I can not read my stream exactly.


      4. When changing the input range and reference voltage, only the time of overflow can be shifted.
      Example: With the setting Input Range +/- 6.144 (-Input +/- 6 * Vref) and the reference voltage internally with 1.024 V receive an overflow will occur at about 0.360mV (= 6mA).

      I hope you can help me.

      19.06.28-Überlauf_markiert-JG.jpg

      19.06.30-Scematic-JG.JPG

       

      Have a nice day
      jg.vs