DESCRIPTION
The Calibrator employs a precision zener diode as a basic reference source. This provides the input to an F.E.T. chopper amplifier system which operates in a feedback stabilised mode. The gain value is determined by a set of precision metal film resistors which are selected by the 5-decade thumbwheel switch. The output voltage is variable from 0 to 9.9999 V in 5 ranges. This can be extended to 1000 V by means of an external mains-powered unit which is available as an extra. The Calibrator’s output resistance is typically 50 milliohms on the top 3 ranges and the
maximum output current that can be drawn on these ranges is automatically limited to 35 mA—this is to prevent damage to the circuitry in the event of accidental short circuit, etc. The lower ranges have an output resistance of
1 ohm and will supply current up to the short circuit value. To ensure complete reliability the Calibrator range switch employs two contacts in parallel for each position—even if a contact fails the calibrator still functions correctly.
The 2003N version incorporates a high performance null amplifier system which allows potentiometric measurements to a resolution of 1 microvolt. Null is obtained by adjusting the thumbwheel digits until the display meter indicates zero. The meter is scaled 20-0-20 and by suitable adjustment of the sensitivity control can display directly in mV or /z V.
The 100 V and lkV Output Units are mains-powered units which extend the output capability of the 2003. They
are connected to the Calibrator output terminals and accurately multiply the Calibrator output voltage.