Kerry D. Wong has posted an article: Using REF200 as 100uA precision reference
The simplest way to use REF200 is to utilize either of its two independent current sources. In this case we obtain a 100 µA reference current. Because REF200 has a built-in current mirror, you can obtain currents of 50µA, 100µA, 200µA, 300µA or 400µA easily.
Because the current reference is placed in series in the circuit in relation to the external component under test, there is no need for a switch to turn on or turn off the circuit. Thus when no external circuitry is connected, there is no standby current so we do not have to worry about batteries when the current reference is not in use.