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Can a power supply change the reference voltage of an ADC?
This can cause inaccuracy, for example, if the MCU accepts 3.3 V analog inputs to the internal ADC while the V REF for that internal ADC is actually the supply voltage to the MCU or 5V. In the end, the power supply, which can reasonably vary by as much as 3%, can cause a fairly significant change to conversion results.
How is the reference device related to the ADC?
The voltage reference is external to the ADC, and along with an amplifier to drive the reference, contributes to the overall system noise. Figure 1: Both the voltage reference device and the amplifier (reference buffer) can contribute to overall system noise for the ADC. (Source: e2e.ti.com)
What is the reference voltage for a 10-bit ADC?
The value produced by a 10-bit ADC with a 5V reference and a 3.3V analog input signal (where 3.3V is the highest value measured at the input) would be: (V IN x 1,024) /V REF = (3.3 V x 1,024)/5 V = 675.84 However, the result, if V REF were 3.3 V, rather than 5 V, would be:
What should the V ref be for an ADC?
The V REF for your ADC should be very stable regardless of the temperature it experiences. It should demonstrate excellent performance over temperature. In short, the lower the number of ppm/°C, the better. Additionally, the initial output voltage accuracy of VREF should be low, in the range of 0.5% or less for precision ADC applications.
Can a MCU be used as a reference voltage?
Some MCUs have an external pin that allows you to provide a voltage reference of your choosing, but others will simply use the MCU’s supply voltage. This can cause inaccuracy, for example, if the MCU accepts 3.3 V analog inputs to the internal ADC while the V REF for that internal ADC is actually the supply voltage to the MCU or 5V.
What is the input voltage of an ESP8266 ADC pin?
The ESP8266 ADC pin input voltage has a range from 0 to 1V, IF! using the bare WiFi Module. However, most ESP8266 development boards, like the NodeMCU ESP8266, come with an internal voltage divider allowing the input range to go from 0 to 3.3V.
How is voltage measured in a ground loop?
When a ground loop exists, the measured voltage, Vm, is the sum of the signal voltage, Vs, and the potential difference, Vg, which exists between the signal source ground and the measurement system ground (see Figure 6).
Can a ADC read lower than 1V?
Most ADCs can NOT read values lower than Vref-. In your case, Vref- is ground, so you can not read -1V correctly. You should use external circuitry to shift the signal to be entirely within Vref- and Vref+. NEW USERS: Posting images, links and code – workaround for restrictions. To get a useful answer, always state which PIC you are using!