• State
  • Replies 3 replies
  • Subscribers 46 subscribers
  • Views 35 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

Original question:

ADS1263: To measure 1uA to 15A DC current using ADS1263

ADS1263: Do we have any software example to calculate current using ADS1263 in diff end mode ?

Jagir Mehta1
Prodigy 200 points
Part Number: ADS1263

Tool/software:

Hello,

I am using ADS1263 for the current measurement.

My team mate has already raised a ticket having hardware queries about ADS1263,

Ticket link : https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1356613/ads1263-to-measure-1ua-to-15a-dc-current-using-ads1263/5197919?tisearch=e2e-sitesearch&keymatch=ADS1263#5197919

I have connected 20mOhm shunt resistor between the AI0 & AI1 pin of ADS1263.

The ADS1263 config is as below, 

Gain : 32, Datarate : 4800 SPS, Ref Positive : 2.5V Internal. Neg Positive : 2.5V Internal

AI0 as Positive Input & AI1 as Negative Input, Conversion Delay : 35 us, Digital Filter : Sinc4

I have used a DP832 power supply & DL3021 DC load, a Power supply input voltage 3.3v & current of 500mA.

I have calculated shunt current as Shunt voltage difference (Read by ADS1263) / Shunt resistor.

Please let me know if my understanding of calculating current from shunt voltage difference is correct or not.

Can you please suggest any other equation to determine shunt current from shunt voltage ?

Do we have any example application notes to calculate current from voltage difference ?

The Calculated current vs Actual current are as below,

Actual current : 5 mA | Calculated current : 8.1 mA

Actual current : 10 mA | Calculated current : 8.6 mA

Actual current : 50 mA | Calculated current : 10 mA

Actual current : 100 mA | Calculated current : 15 mA

Actual current : 500 mA | Calculated current : 45 mA

  • 0
    TI__Mastermind 37141 points

    Hi Jagir Mehta1,

    Can you send a schematic of your system so we can review?

    Jagir Mehta1 said:
    I have calculated shunt current as Shunt voltage difference (Read by ADS1263) / Shunt resistor.

    This is correct, assuming you have converted the ADC code value correctly to a voltage. Can you provide the raw hex data you receive from the ADC for each measurement range e.g. 5 mA, 10 mA, etc.? Also, can you confirm that the shunt value is 10mOhm? If so, are you measuring the actual shunt value with a precision DMM first so you know its actual resistance e.g. it could be 9.9mOhm for example, which would affect your measurement accuracy.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 200 points

    Hello Bryan,

    Please find below raw hex data from ADC for different input current range.

    .--> 500 mA Input current

    Volt in Hex [0xc3eca]

    Volt diff [0.000934] V 

    Shunt Current [0.046712] A

    --> 100 mA Input current

    Volt in Hex [0x3c5b4]

    Volt diff [0.000288] V 

    Shunt Current [0.014390] A 

    --> 50 mA Input current

    Volt in Hex [0x2ce79]

    Volt diff [0.000214] V

    Shunt Current [0.010706] A 

    --> 10 mA Input current

    Volt in Hex [0x221d6]

    Volt diff [0.000163] V 

    Shunt Current [0.008134] A 

    I have used the below equation to get voltage from ADC output.

    Voltage = (ADC_Output * Ref Voltage) / ADC_positive_step_count

    Reference voltage = 2.5V

    ADC_positive_step_count = 0x7fffffff (positive num range of uint32)

    I have used 20 mOhm shunt resistor.

  • 0 in reply to Jagir Mehta1
    TI__Mastermind 37141 points

    Hi Jagir Mehta1,

    The data values you provided are only 20 bits (e.g. 0xc3eca]), while you should be getting 32-bit values from the ADS1263. Can you please provide the complete 32-bit value you receive from the ADC, even if the first few bits are 0?

    -Bryan