Design of a high precision current source

Current source is one of the key components in electrical measurement and control systems. However, the noise introduced by temperature drift and other interference makes it a significant source of systematic errors. To develop a high precision and stable current source, a Howland-based voltage to current conversion (V/I) circuit is presented in this paper. The current source is fully programmable using a DSP via RS-232 interface. Moreover, a sampling circuit is provided, using the sampling results, calibration is made to further reduce the output error of the current source. Under a constant 140 Omega load, experiment results shows that current output ranges from -50 mA to +50 mA with error less than 3 muA, and features low temperature drift and distortion. This proves that such design can be an effective way to provide a precise and stable range output current.