Abstract: A pin electronics test circuit applies test signals at a pin of an ECL integrated circuit (IC) device under test (DUT) and senses and measures pin signals received from a pin of the DUT. The pin electronics test circuit incorporates test signal first and second electrical paths (TL1, TL2) (TL11, TL12) with respective test connect and disconnect first and second nodes (n1)(n2). First and second termination circuits (RL1, A1)(RL2,A2), first and second DC test signal generators (A1 etc.) (A2 etc.) for forcing DC test signal voltages and currents, AC test signal generator (I.sub.HI, I.sub.LO etc.) for switching between and driving AC test signals of high and low potential levels, and pin signal sensing and measuring circuits (CR1, 8CR2) are all contained on a single pin electronics card (PEC) (54) or formed as a single unit for a pin or complementary pair of pins of the DUT.

Abstract: A miniaturized thick-film isolation transformer comprising two rectangular substrates each carrying successive screen-printed thick-film layers of dielectric with spiral planar windings embedded therein. The spiral windings comprise conductors formed of fused conductive particles embedded within a layer of dielectric insulating means solidified by firing at high temperature to form a rigid structure with the windings hermetically sealed within the dielectric and conductively isolated from each other within the transformer. The substrates are formed at opposite ends thereof with closely adjacent connection pads all located at a single level to accommodate automated connection making. Connections between the pads and the windings are effected by conductors formed of fused conductive particles. The substrates and the dielectric layers are formed with a central opening in which is positioned the central leg of a three-legged solid magnetic core.

Abstract: An apparatus and method for determining the number of turns on a sample coil are disclosed. An alternating current of substantially constant amplitude is passed through a primary winding turn which is coupled to the sample coil and also through a primary winding turn which is coupled to a standard coil of known turns count, inducing currents in the sample coil and in the standard coil in inverse proportion to their respective turns counts. These induced currents are commutated into pulsating direct currents that are fed into a ratiometric current meter. This meter produces a measurement output corresponding to the ratio of the current induced in the standard coil to the current induced in the sample coil. This measurement output is displayed on a calibrated readout device as an indication of the number of turns on the sample coil. In addition, means are provided for indicating coil discontinuity and inverted coil phase.

Abstract: Apparatus for determining the number of turns of a test coil wound on a magnetic core comprising a reference coil with a pre-fixed number of turns wound on a reference core and coupled to a resistive load. The test coil is linked to the reference coil by a single-turn primary supplied with a-c current of substantially constant amplitude. An adjustable resistive load is connected across the test coil. Both load resistors are of low ohmic value, to operate the two coils as heavily-burdened current transformers. The coil voltages are compared by a phase-sensed comparator, and the adjustable resistor is set to produce a null comparison condition. At this condition, the number of turns of the test coil will be proportional to the resistance of the adjustable resistor, and this number is indicated by a calibrated digital read-out device.

Abstract: A signal isolator including a coupling transformer with modulate/demodulate switches in series with the primary and secondary windings. The switches are driven in synchronism by an oscillator. Resonating capacitors are connected in parallel with the transformer windings to form an LC tank circuit tuned approximately to the operating frequency of the switch-drive oscillator. When the switches are closed, the current in the transformer windings ramps in a linear fashion in response to application of the input voltage, and when the switches are opened, the current varies in a cosine curve to provide smooth transitions at both ends to the ramp current, thus controlling the flux in the transformer core so as to minimize instability effects.

Abstract: A signal isolator including a coupling transformer with modulate/demodulate switches in series with the primary and secondary windings. The switches are driven in synchronism by an oscillator. Resonating capacitors are connected in parallel with the transformer windings and tuned to the switch operating frequency to control the flux in the transformer core. A transformer turns-ratio of less than unity introduces a corresponding attenuation, and a following amplifier counteracts that attenuation to produce an output signal at the original level. A return current resistor is connected between the output signal and the transformer secondary to produce a back-flow of current towards the transformer. This current provides for supplying the losses of the coupling circuit in a symmetrical fashion, both from the isolator input and its output, to reduce significantly variations in performance resulting from changes in ambient temperature.

Abstract: An isolation amplifier comprising an input section coupled by a multi-winding transformer to an output section. A blocking oscillator produces in the transformer a signal comprising a positive power pulse followed by a negative flyback pulse. The flyback pulse magnitude is modulated by a half-wave diode-capacitor rectifier circuit which supplies negative supply current to an amplifier in the input section. Other half-wave diode-capacitor rectifier circuits in the input section develop (1) a positive supply voltage for the amplifier, (2) a negative feedback signal for the amplifier, and (3) a level-shifting voltage to be combined with the feedback signal. The output section includes additional half-wave diode-capacitor rectifier circuits to develop a demodulation signal derived from the flyback pulse, and a bias voltage to be combined with that signal to develop an input signal for the output amplifier.

Abstract: An electrical system for automatically measuring, computing and indicating the oxygen content in a sample of fluid, using a galvanic cell that absorbs and consumes the oxygen from the sample, produces controlled current pulses of given duration that are conducted by the cell as necessary to maintain the cell voltage constant and these pulses are counted during controlled intervals and the count is displayed as a representation of the oxygen content of the sample.