LM10 integrated circuit can be used to create a meter amplifier. The accuracy of full-scale sensitivity of this circuit is good for 15°C to 155°C at 10mV and 100nA. Here is the schematic diagram :
The resistor R4 is used to balance the bias current, and the R5 is for correcting the offset voltage error.The zero calibration uses the reference voltage of the IC, therefore it will be independent of battery voltage level, avoiding frequent adjustment as the battery voltage drains out. This circuit only consumes battery below 0.5 mA, and can last long to 3-6 month with AA cell battery or even one year with D cell battery.
[Source : National Semiconductor Application Note]