0.004A*250 ohms = 1V0.020A*250 ohms = 5V
Then read the analogue input with the internal 1.1volt Aref enabled in setup().
Doesn't the Arduino have a voltage regulator even after being powered via USB?
The manufacturer of the pressure transducer advertises:High Accuracy ±0.08% BSL Includes Linearity, Hysteresis, and RepeatabilityI want to avoid losing accuracy of the sensor and I read somewhere if the resistor tolerances are off then our reported results are off too.
Sorry even with 53 ohms wouldn't I lose the resolution of my results?.004 A * 53 ohms = 0.212 Volts.020 A * 53 ohms = 1.060 Volts
Measurement Accuracy: ±0.5% F.S. @ 16-bit ADC, ±2% F.S. @ 10-bit ADC
In the default mode, the setting is +/-6.144 volts.Thus the value of 32767 would represent a value of 6.144 volts.Dividing 6.144 volts by 32767 yields a scale factor of 0.1875 mV per bit. This is a significant improvement over the Arduino ADC which resolution of approximately 5 mV per bit. In fact, its about 26 times better!The neat thing about this is that this is worst case. In another PGA setting, you can establish a full scale of +/- 2.048 volts. That provides us a resolution of 0.0635 mV.ADS1115 Maximum Measurement RangeThe PGA setting of +/- 6.144 range can be a little misleading as it seems to infer that you can measure voltages that high. You can't.Instead, the maximum measurable voltage is established by the supply voltage to the chip. Specifically, the maximum measurable voltage is 0.3 volts more than the supply voltage. In fact, exceeding this voltage at your analog input may damage your chip.Note the differentiation here between the PGA range and the maximum measurable voltage. The programmed range determines the value of a bit (or scale factor), while the maximum measurable range determines what your analog input can safely handle.
In another PGA setting, you can establish a full scale of +/- 2.048 volts. That provides us a resolution of 0.0635 mV.
Ok, so if I understood things properly assuming I decide to use the PGA settingwith a full scale of +/- 2.048 volts → 16 bit ADC → 216 = 65,536 → ±2.048V → +2.048V (32,768) → 2.048V/32,768 = .0625mV / bit = .0000625V / bit → 689.476 kPA (100 psi) max. pressure spec. of transducer →689.476kPa / 2.048 = 336.658203125 kPa/V→ 336.658203125 kPa/V * .0000625V/bit = 0.0210411376953125 kPa/bit→ 0.0210411376953125 kPa / 689.476 kPA = 0.000030517578125→ 0.000030517578125 * 100 = 0.0030517578125 % (theoretical resolution of pressure transducer readings)***************************************************************************Using 100 Ω resistor,V = IR2.048V = I *100 Ω = .02048A = 20.48 mAV = .004A * 100 Ω = .4V
Is it 15 or 16 bits?The output of the ADS1115 is what as known as a signed integer. That means one of the bits in the 16 bit words is going to be used to tell us if it's a positive or negative value being reported. This will be discussed more later, but what is important to grasp is that only 15 of the 16 bits are used to communicate the value of the voltage measurement.What this means is that there are 32,768 possible output values, where zero is the first and 32,767 is the last.Bottom line is that is indeed a 16 bit device, but only 15 of those bits are use to communicate the magnitude of the measurement.
What do you mean by 16/20?
16 bit ADC → But only 15 bits are used for communicate measurement?