Yokogawa 700987 Logic Probe – Isolated Inputs

The Yokogawa 700987 Logic Probe – Isolated Inputs is a specialized accessory for digital circuit analysis and troubleshooting with Yokogawa ScopeCorder series instruments. Each of its 8 input channels features complete electrical isolation, preventing ground loops and protecting both the probe and connected equipment from voltage-induced damage. The probe detects logic states - high, low, and pulse conditions - across a wide voltage range, with independently isolated inputs and a 2000 VAC withstand rating per terminal.

Technical Specifications

• Input Channels: 8 bits, fully isolated from each other and the host instrument


• Response Speed: DC ≤1 ms; AC ≤20 ms


• Threshold Levels: 6 VDC ±50% or 50 VAC ±50%

DC mode: High 10–250 VDC, Low 0–30 VDC

AC mode: High 80–250 VAC, Low 0–20 VAC

• Maximum Input Voltage (≤1 kHz): 250 Vrms, AC peak ≤350 V, DC ≤250 V


• Input Fuses: 250 V rated, 50 mA maximum, time-lag type (internal, non-user-replaceable)


• Isolation Withstand: 2000 VAC for 1 minute (input to earth)


• Insulation Resistance: ≥10 MΩ at 500 VDC (input to earth)


• Mode Selection: AC/DC switchable per input

Key Features

• Complete galvanic isolation on all 8 inputs eliminates cross-channel interference and earth-loop contamination


• Wide voltage acceptance accommodates both low-level TTL/CMOS logic and industrial control circuits up to 250 V


• Input-terminal fusing protects against transient overvoltage conditions


• Fast response time enables reliable pulse and edge detection in real-time digital troubleshooting

Typical Applications

• Multipoint digital circuit verification in isolated or high-voltage environments


• Ground-loop-free acquisition of logic signals across multiple circuit nodes


• Safety-critical circuit validation where isolation integrity is mandatory

Compatibility & Integration Connects to ScopeCorder instruments via 26-pin connector with clamp filter (A1190MN). Measurement leads vary by voltage: Model 366961 for ≤42 V, Model 758917 for ≥42 V. Adapter leads 758922, 758929, or 701954 also supported. Do not stack probes during operation; maintain adequate spacing to prevent thermal rise.