Methods for operating a sensor device are provided, which may include (a) providing at a site (e.g., implanting in a patient) a device which comprises at least first and second reservoirs, a first sensor and corresponding first reference sensor located within the first reservoir, a second sensor and corresponding second reference sensor located within the second reservoir, a first reservoir cap closing an opening in the first reservoir and a second reservoir cap closing an opening in the second reservoir, and a power source, control circuitry, and electrodes for selectively disintegrating each reservoir cap; (b) disintegrating the first reservoir cap and operating the first sensor and reference sensor; and (c) using the first reference sensor to determine whether the first sensor is operating properly. If not operating properly, then the control circuitry initiates disintegration of the second reservoir cap and operation of the second sensor and reference sensor.