Flash testers are commonly used for measuring solar cells and modules but in their usual implementation are complex, expensive, and susceptible to transient errors. This work presents a new tester design that is simple, low cost, and reduces transient errors by use of a constant-voltage cell-bias circuit. A novel feature of the system is that it extracts a family of I-V curves over a decade range of light intensity, which provides comprehensive information on cell performance. The new design has been tested and used extensively. (C) 2003 Elsevier B.V. All rights reserved.