| 摘要 |
PURPOSE:To obtain a tester of high accuracy with its easy maintenance by using a reference voltage generator to give calibration to a voltage input device. CONSTITUTION:The output voltage signal of a reference voltage generator 15 is measured by a voltage input device 10 via a contact of a relay 14 after the relay 14 is energized by a digital output before a process controller is tested. Then a CPU8 calculates a correction coefficient equal to reference voltage/measured voltage. The voltage value measured during a test operation is multiplied by the correction coefficient, and therefore the calibration is given to the output signal of an operator of the process controller which is supplied from output terminals (c) and (d) respectively. In this case, the reference voltage is read through a resistance 16 having the same rated value as a protecting resistance connected to terminals (c) and (d) and incorporated to the process controller. As a result, an error due to the variation of the input impedance of the device 10 is also corrected. |
