| 摘要 |
A transmitter includes a sensor for sensing a primary process variable representative of a process, and providing a sensor output current. An integrator in the transmitter integrates the sensor output current. The integrator has an amplifier on an integrated circuit and an off-chip capacitor coupled between the inverting input on the amplifier and the amplifier output via two integrated circuit pads, which leak undesirable leakage current to the integrator. A leakage cancellation circuit is selectively connectable to the inverting input of the amplifier in the integrator, the cancellation circuit providing a current substantially opposite in polarity and equal in magnitude to the leakage current as a function of a stored voltage representative of the magnitude of the leakage current. A microprocessor based compensation circuit compensates the output of the integrator for repeatable errors which affect the process variable. A formatting circuit couples the compensated process variable to a two wire current loop.
|
