An apparatus for converting a complex AC voltage wave to an equivalent DC value which is a measure of its true RMS value and which may then be read on an accurate indicating device such as a digital voltmeter, incorporating thermal converters and operational amplifiers in a temperature-compensated configuration. The apparatus maintains a portion of an unknown AC voltage wave, which is thermally converted into a DC voltage, substantially equal to a DC reference voltage. A portion of a DC output v...

A voltage level converter for converting an input signal at a first voltage level to an output signal at a second voltage level, the converter comprises: an input for receiving said input signal; an output for outputting said output signal; a circuit node; precharge means for charging or discharging said circuit node to a third voltage level during a first time period by connection of said circuit node to a first voltage supply; isolation means for isolating said circuit node from said first vol...

An analogue-to-digital converter of the dual slope integration type has an integrator portion and analogue input signal of one polarity and a reference signal of opposite polarity, the two signals being alternately connected to the integrator portion. The invention includes means for generating a variable reference signal, the magnitude of which is varied in dependence on the magnitude of the analogue input signal, for producing a predetermined non-linear relationship between the analogue input ...

An RMS converter of the type wherein the energy of the input signal is dissipated in a first resistor and a second signal, in a form which lends itself to measurement, is generated which dissipates an equal amount of heat in a second resistor, the second signal being derived from measurement of temperature differential between the first and second resistors. This converter is characterised by a circuit for applying power to both resistors so that the total power received by each resistor remains...

An analogue-to-digital converter of the parallel-series-parallel type has additional circuitry associated with the second quantization stage which accepts overflow caused by errors in the first quantization stage and generates a correction signal to correct the output of the first quantization stage.

An improved thermionic electric converter uses a wire grid cathode to provide a larger surface area for electrons to boil off. Alternately or additionally, the larger electron emission surface area can be achieved by using a curved electron emission surface. A laser provides quantum interference to electrons just before they reach the anode, thereby lowering their energy levels such that they more readily are captured by the anode. The arrangement provides improved conversion efficiency and redu...

A thermal image converter comprises a slice of pyroelectric material to act as a reflector for an electron beam. Exposure of one face of the slice to a thermal scene induces a charge distribution over the other face of the slice corresponding to temperature gradients in the thermal scene. The charge distribution modulates and deflects electrons in an incident electron beam which may be viewed by directing the reflected beam onto, for example, a fluorescent screen. A practical construction of sea...

A digital-to-analog converter utilizing a set of high-speed current switches each comprising a buffer transistor and a switching transistor interconnected with a common resistor in such a fashion that the buffer transistor in the normal "off" state supplies the common resistor with a current of predetermined magnitude to bias the switching transistor to cut-off; a control pulse coupled through an input diode cuts off the buffer transistor, the bias at the switching transistor is thereby eliminat...

A delta modulation type data converter is adapted to carry out signal processing by sequentially comparing in cycles an inputted signal with a reference voltage set according to the results of previous comparisons and includes a plurality of current sources, switch circuits for setting a current value by appropriately selecting one or more of these current sources, an integrator circuit for generating the reference voltage according to a specified current value, and a control circuit for control...

The analog-to-digital converter comprises a comparator having first and second inputs, and an output. A first switch is capable of connecting a signal to be measured to the first input and a second switch can connect a reference source to said first input. A capacitor is connected between said second input and the reference source and serves to store a charge fed by way of a feed back loop from the output of the comparator. The feed back loop includes current generator means arranged to provide ...