Abstract: A portable current measuring apparatus brings many current sensing devices close to a wire in order for the magnetic flux of the current within the wire to induce a current in the devices. The devices are arranged in a bridge circuit and connected with a signal source and a differential amplifier so that when the output of the devices is added by the amplifier the noise generated by magnetic sources is eliminated. The housing for the apparatus is small and light weight and includes a place for a portion of the current carrying wire to be positioned for current detection. Use of the apparatus does not require that the wire be cut, nor is it required that the apparatus become a permanent fixture of the circuit having the current carrying wire.

Abstract: A fast, high-resolution A/D converter circuit includes a combination of a main-range up/down counter and a subrange A/D converter. An output from the up/down counter for upper bits is D/A-converted and subtracted from an input signal, and the remainder of subtraction is A/D-converted by the subrange A/D converter, thereby obtaining high-resolution conversion data. The circuit has a feedback loop which detects that the remainder becomes less than LSB of the up/down counter and stops a count operation. By discriminating that the remainder is more/less a predetermined level set higher than the LSB of the counter or outside/inside a predetermined range, a count rate is switched between high and low rates. The remainder enters subrange via the low rate count stage.

Abstract: The invention comprises an isolation amplifier including an input circuit and an output circuit coupled through an isolation transformer. A switching type balanced modulator modulates a square wave carrier with an analog signal input and delivers the resulting signal to the input of the isolation transformer. A demodulator in the output circuit inverts alternate points of the modulated square wave carrier to essentially reproduce the analog input. A sample and hold capacitor circuit connected to the output of the demodulator fills the gap between the trailing and leading edges of successive pulses.