Constant Current Source

"Precise" Constant Current Source based on TI XTR110AG

Main Components

Revision 0.1

Arduino Nano

Simple Arduino for processing of the SCPI commands and coordinating the range switching.

MCP3202

Two channel SPI 12 Bit ADC with external reference voltage.

REF02

Reference voltage source used for internal "calibration" and as reference for arduino ADC and MCP3202

Measurments

Revision 0.1

Stability over 2 Hours

Measured against reference voltage source REF02

Parameters:

• Duration: 2 Hours
• Frequency: 1s (approx.)
• Attentuatuation before LM324N: 8 (rough setting)
• LSB at ADC: approx 9,765mV (with Attentuation of 8)
• Internal Averaging Samples: 50

Voltage A (Sense A):

Value	Measurment
Standard Deviation	1,456 mV
Maximum Value	5.216500 V
Minimum Value	5.207500 V
Mean Value	5.213059 V
25% of Counts	5.212000 V
50% of Coutns	5.213200 V
75% of Counts	5.214200 V

Boxplot and Histogram

Voltage B (Sense B):

Value	Measurment
Standard Deviation	411 uV
Maximum Value:	5.150300 V
Minimum Value:	5.146000 V
Mean Value:	5.147937 V
25% of Counts:	5.147700 V
50% of Coutns:	5.147900 V
75% of Counts:	5.148100 V

Boxplot and Histogram

Overview over 2 Hours

Result

In some mysterious way, Sense A voltage measrument is way more bad than Sense B. Next measurment will be done over 24h with better shielding against the USB connection which is directly over the input attentuation voltage divider.

Credits

Used Librarys:

vrekrer/Vrekrer SCPI parser@0.4.1

robtillaart/PCF8574@0.3.2

mokolea/InputDebounce@1.6.0

ouviksaha97/MCP3202@1.0.2