We demonstrate a capillary device used to measure the shear rate dependent viscosity of microliter scale volumes. Liquid samples are driven pneumatically to fill a microcapillary and partially fill a larger glass capillary. The glass capillary is mounted on an optical linear sensor array to track the air-liquid meniscus in real time. The pressure differential driving the flow is reversed by switching a pneumatic valve. Each transit is used to measure the volumetric flow rate, which in combination with the pressure drop, is used to determine viscosity as a function of shear rate. A given sample of at least 50 $\mu$L can typically be measured over 2 to 3 decades in shear rate, in the range of 10 s$^-1$ to 10$^5$ s$^-1$, and be essentially fully recovered. Validation is performed using samples of Newtonian and non- Newtonian fluid and compared to reference measurements. An analysis of the range of operation and uncertainty arising from instrumentation, interfacial pressure, meniscus effects, and inertial effects.