Description
SnipCard ADC Sigma Delta 24 bit for Archiduino System (or Arduino, if used as breakout board).
This SnipCard gives Archiduino an accurate 24 bit ADC thanks to the LTC2484 made by Linear Technologies. With breadbording cables you can easily adapt it to work with every Arduino board model.
ADC Sigma Delta 24 bit SnipCard – Techical informations:
The LTC®2484 combines a 24-bit No Latency ∆Σ™ analog to-digital converter with patented EasyDrive™ technology. The patented sampling scheme eliminates dynamic input current errors and the shortcomings of on-chip buffering through automatic cancellation of differential input current. This allows large external source impedances and input signals with rail-to-rail input range to be directly digitized while maintaining exceptional DC accuracy. The LTC2484 includes an on-chip oscillator. The LTC2484 can be configured to reject line frequencies. 50Hz, 60Hz or simultaneous 50Hz/60Hz line frequency rejection can be selected as well as a 2× speed-up mode. The LTC2484 allows a wide common mode input range (0V to VCC) independent of the reference voltage. The reference can be as low as 100mV or can be tied directly to VCC. The LTC2484 includes an on-chip trimmed oscillator, eliminating the need for external crystals or oscillators. Absolute accuracy and low drift are automatically maintained through continuous, transparent, offset and full-scale calibration. (from LTC2484 datasheet).
The 24 bit Sigma Delta ADC SnipCard voltage reference is provided by a LT1236 made by Linear Technology.
The LT® 1236 is a precision reference that combines ultralow drift and noise with excellent long-term stability and high output accuracy. The reference output will both source and sink up to 10mA and is almost totally immune to input voltage variations. The LT1236 combines both superior accuracy and temperature coefficient specifications without the use of high power, on-chip heaters. The LT1236 references are based on a buried zener diode structure which eliminates noise and stability problems with surface breakdown devices. Further, a subsurface zener exhibits better temperature drift and time stability than even the best band-gap references. (from LT1236 datasheet)
ADC Sigma Delta 24 bit SnipCard – Document reference
SnipCard ADC 24 Bit Sigma-Delta V 0.6 schematic
Scheda Tecnica SnipCard ADC 24 Bit – V4 – Bisotronic (IT)
ADC Sigma Delta 24 bit SnipCard – Software snippet
void loop()
{
uint8_t adc_command; // The LTC2484 command word
int32_t adc_code = 0; // The LTC2484 code
float adc_voltage = 0; // The LTC2484 voltage
float adc_summe = 0; // sum of voltages in for-loop
float adc_average = 0; // averaged voltage after for-loop
uint16_t miso_timeout = 1000; // Used to wait for EOC
int i;
adc_command = OSR_mode; // Build the OSR command code
float grammi = 0;
for (i=0; i<nsamples; i++) {
LTC2484_read(SS_pin, adc_command, &adc_code); // Throws out reading
adc_voltage = LTC2484_code_to_voltage(adc_code, LTC2484_vref);
adc_summe = adc_summe + adc_voltage;
delay(200);
}
}
