The Measurement Computing USB-PDISO8 is a USB 2.0 full-speed digital I/O device designed for high-voltage and relay control applications in electrically noisy industrial environments. It provides eight optically isolated digital inputs rated to 500 V isolation and eight SPDT Form C relay outputs, each rated at 6 A at 30 VAC or 28 VDC. The device operates from USB +5 V (4.75–5.25 V) with minimal draw of 10 mA maximum, plus an external 9 V power supply (nominal) for relay operation. All eight relay outputs remain de-energized at power-on, defaulting to the normally closed contact.
Technical Specifications
Digital Inputs
• 8 channels, optically isolated at 500 V
• Input range: up to 30 V AC or DC
• DC thresholds: high ≥ +5.0 VDC or –5.0 VDC; low ≤ +1.5 VDC or –1.5 VDC
• AC thresholds (50 Hz to 1000 Hz): high ≥ 6.0 Vrms; low ≤ 1.5 Vrms
• Response time: 20 µs (filter disabled) or 5 ms (filter enabled)
• Software-selectable 5 ms time constant filter (200 Hz) per input; disabled at power-up
• Input impedance: 1.6 kΩ minimum; polarity-insensitive
Relay Outputs
• 8 channels, SPDT Form C relays at 500 V isolation
• Contact rating: 6 A at 30 VAC or 28 VDC
• Life expectancy: 10 million mechanical operations minimum
• Default state: not energized; normally closed contact active
Power Management
• USB supply: 4.75–5.25 V, 10 mA maximum
• External supply: 9 V nominal (±10%); requires MCC p/n CB-PWR-9 (9 V @ 1.67 A)
• External consumption: 200–230 mA (relays off); 820–900 mA typical (relays on)
• Daisy-chain output: 4.0 A maximum; 0.5 V drop maximum
• Power supervisor threshold: 6.5–12.5 V (PWR LED on); fault indication outside this range
– Key Features
• 500 V optical isolation protects against transient interference and ground loops
• Software-configurable input filtering reduces noise in AC environments
• 20 µs input response time supports fast monitoring in unfiltered mode
• De-energized relay default ensures safe operation during power loss or reset
• Daisy-chain power output supports cascaded module configurations
– Compatibility & Integration
Supports USB 1.1 and USB 2.0 connections; hardware revision C and later compatible with USB 3.0. Works with Mathworks Data Acquisition Toolbox and includes InstaCal, Universal Library, UL for LabVIEW, TracerDAQ, and SoftWIRE programming support. Windows operating system required.
