Electric circuit testing equipment

Claim 2

An electric circuit testing equipment comprising at least one signal pick-up probe unit (25, 41 or 105) adapted to be coupled with a selected point of a circuit to be tested (23) and means (31) utilising an output signal derived from the probe unit for test purposes characterised in that the probe unit (25, 41 or 105) is adapted to be capacitively coupled with said selected point and said output signal is derived from said probe unit (25, 41 or 105) by signal conditioning circuit means (R2, C2, and 47 to 61 or 121 to 127 and 49 to 61) responsive to the signals picked up by the probe unit (25, 41 or 105) to produce an output signal corresponding only to signals picked up by the probe unit (25, 41 or 105) from said selected point.

Claim 3

An equipment according to Claim 1 wherein said circuit means comprises means (R2, C2 and 47 to 61) for producing an output signal corresponding only to signals picked up by the probe unit from said selected point whose amplitudes exceed a predetermined threshold value.

Claim 4

An equipment according to Claim 2 wherein said circuit means comprises: means (R2, C2) for differentiating the signals picked up by the probe unit; comparator means (49, 51) for producing an output in response to each excursion in an input signal derived from the differentiated signals beyond a first threshold value of a first polarity or beyond a second threshold value of the opposite polarity to but substantially the same magnitude as the first threshold value; and flip-flop means (60) responsive to the output of the comparator means.

Claim 5

An equipment according to Claim 3 wherein said probe unit (105) comprises a first probe (109) adapted to be positioned adjacent said selected point (115) and at least one further probe (107 or 111) adapted to be positioned, with the first probe (109) positioned as aforesaid, adjacent a point (117 or 119) of the circuit to be tested adjacent said selected point (115), and said circuit means includes means (121) connected between said differentiating means (R2, C2) and said comparator means (49, 51) for subtracting a proportion of the differentiated signals of said further probe (107 or 111) from the differentiated signals of said first probe (109).

Claim 6

An equipment according to Claim 4 wherein said means for subtracting comprises a differential amplifier (121).

Claim 7

An equipment according to any one of Claims 1 to 3 wherein said probe unit (25) comprises a tubular member (151) of electrically conducting material; a pair of elongated members (153) of electrically conducting material secured to one end of said tubular member (151) so as to extend perpendicular to the axis of the tubular member (151) in parallel spaced relationship such that the axis of the tubular member (151) intersects the axis of the gap between said elongated members (153) substantially at right angles; and an insulated conductor (155) extending through said tubular member and along the gap between said elongated members.

Claim 8

An equipment according to Claim 6 wherein there are two such insulated conductdors (155A, 155B) which respectively extend along said gap in opposite directions with respect to the axis of the tubular member (151).

Claim 9

An equipment according to any one of Claims 1 to 5 wherein said probe unit (25, 41 or 105) forms part of a multi-test probe unit adapted to pick up simultaneously the signals appearing on the leads of an integrated circuit package (23),said multi-test probe unit comprising: a body portion (61) of electrically insulating material including a wall portion (63) disposed on a side of a cavity (65) adapted to receive the package with a line of leads (71) of the package (23) facing said wall portion (63); a plurality of bores (69) within said wall portion (63) disposed in parallel spaced relationship corresponding to the spaced relationship of the leads of the adjacent line of leads (71) of the package (23); and extending along each bore a coaxial conductor pair (73, 91) the outer conductor (73) of which is removed at the extremity of the pair adjacent said cavity (65) over a region adjacent and substantially centred on the corresponding lead (71) of the package (23).

Claim 10

An equipment according to Claim 8 wherein said integrated circuit package (23) is a dual-in-line package and said body portion (61) has two parallel planar spaced said wall portions (63), said cavity (65) being adapted to receive said package (23) with each line of leads (71) of the package (23) facing a respective one of said two wall portions (63).