|
The amplifiers have very low offsets for accurate tracking of programming instructions and exceptionally stable output in fixed applications. Voltage may be operationally controlled using the built-in stable reference and summing resistance together with an external voltage feedback rheostat.
The ratio of reference voltage to summing resistance gives a control current of approximately 1 milliampere through the external voltage feedback rheostat, for a control ratio of 1000 ohms/V. (A built-in calibrating trimmer can be used to calibrate this value).
PTR models are equipped with a built-in current sensing and control channel for precision current stabilization, with automatic crossover from and to the voltage stabilization mode. A built-in trimmer adjusts current over the range 2% Io to 100% Io max. Current may be externally controlled (programmed) by a remote potentiometer or by a small d-c voltage. The potentiometer functions as part of a divider across the internal reference delivering 0-0.5V to the current control terminal. This voltage (with respect to plus output) can be derived from a separate programming source (as, for example, a Kepco SN or SNR programmer).
For a wider current control range, the voltage channel of the PTR may be connected so as to sample the drop across an external current-sensing resistor in the plus output lead. An external rheostat with careful zeroing of the built-in zeroing potentiometer will control current from 1µA to 100% Io. (Note: the range of currents controlled by any single current-sensing resistor should be limited to a 50:1 ratio).
Operationally, the PTRs are 3-terminal, unipolar, inverting d-c amplifiers in which the plus output sensing terminal serves as common between the output and an external programming signal. For isolated digital control, see Kepco SN and SNR Series.
|