INA169 Vout and Rl math

Robert,

If you examine figure 9 of the datasheet, the main purpose of Rl is to determine the gain you would need for these measurements. Therefore, with your defined system, your maximum differential occurs at 130 amps, where V_sense would be

V_sense = 130A * .500mohm = 65 mV

and you want that value to correspond to your highest voltage output, so

Vout = 3.3 V when V_sense = 65 mV. To achieve this, we need to select a gain for the design to achieve this, so

3.3V/.065V = 50.77. We wil round this to 50. Then, according to figure 9 of the datasheet, your Rl would need to be a 50k resistor to achieve this.

Then, when you measure your maximum differential voltage, you'll see that 130A corresponds to

.065*50 =  3.25V

Hope this helps. Let me know if you need anything else.

Carolus