The Model 414A Autovoltmeter is used to accurately measure
dc volts and ohms with immediate, automatic range selection.
Operation is simply "touch and read." Automatic, overload
protection circuits insure that the instrument will not be
damaged by an overrange voltage before upranging can occur.
Both range and polarity are displayed in illuminated
characters above the meter.
In the AUTO mode, a downrange to the next lowest range
occurs when the measured voltage or resistance falls below
25% of full scale; and an uprange to the next highest range
occurs when the measured voltage or resistance rises above
96% of full scale.
A HOLD mode provides manual downranging, a step at a time,
using the DOWNRANGE switch and also adds a noise filter to
the input. When measuring voltage in this mode, an automatic
uprange to the
1500 v range will occur if the measured voltage exceeds full
scale by 40%. On resistance measurements in the HOLD mode,
upranging will never occur, even when the measured
resistance becomes infinite, such as when the probes are
removed from a resistor.