Simulated ohms generation method and apparatus for calibrating resistance type measuring instruments

摘要

A simulated ohms generating method and apparatus for calibrating electrical measuring instruments of the resistance and/or conductance measuring type are disclosed. First, the nature (current or voltage) of the internal power supply of the measuring instrument is determined by sequentially connecting two different resistors to the terminals of the instrument and determining if the current flow through the resistors changes (voltage source) or remains constant (current source). Depending upon the nature of the power supply one or the other of two sequences of steps are followed. While the sequences are somewhat different, they both include adjusting the output of a voltage source connected in series with a fixed resistor and applying the combination to the instrument to simulate a predetermined resistance (ohms) value. After this value is set, the instrument being calibrated is read to determine if the reading is the same as the predetermined resistance value being simulated. If not, the reading is slewed by steps toward the predetermined resistance value by changing the output of the voltage source. When the resistance reading has been slewed to the point where it is the same as the predetermined resistance value, calibration error is determined based on the predetermined resistance value and the simulated resistance value required to achieve a reading equal to the predetermined resistance value.