Open loop DC gain:
Inverting circuit. 10k input, 100k feedback.
Use a very high ohmic voltmeter to measure the voltage at IN-. (Range 0...10mV)
Use a second voltmeter to measure the output voltage.
Now short input (10k) to GND and measure the voltages.
Now input 1V and measure the voltages.
Open loop DC gain:
Inverting circuit. 10k input, 100k feedback.
Use a very high ohmic voltmeter to measure the voltage at IN-. (Range 0...10mV)
Use a second voltmeter to measure the output voltage.
Now short input (10k) to GND and measure the voltages.
Now input 1V and measure the voltages.