PRODUCT INFORMATION
Product Overview
The Allen-Bradley 1771-VHSC is a PLC-5 Very High Speed Counter Module designed for high-speed signal processing. This unit installs directly into a single slot of an Allen-Bradley 1771 I/O chassis. It features twelve digital inputs arranged with three inputs allocated per counter across four configurable channels. The hardware also provides eight isolated digital outputs split evenly across two groups. Count values can range from 0 to 999,999 with an internal module update period of 100 microseconds.
Backplane power supplies 650 mA of current to operate the module without requiring external power supplies. The module provides 1500 Volts of electrical isolation between the backplane logic and external input/output circuits. Supported input modes include rate, period/rate, counter, and two-channel quadrature encoder configurations. Maximum input frequencies reach up to 1 MHz when running in single-channel counter operation. Users can select input voltage levels between 5 Volts DC and 12 to 24 Volts DC.
TECHNICAL DATA
Technical Specifications
| Parameter | Specification |
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| Category | PLCs |
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| Product Line | PLC 5 |
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| GTIN | 10612598114907 |
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| Weight | 1.00 lbs (0.45 kg) |
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| Typical DC Signal Delay (Off) | 30 (+/- 7) milliseconds |
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| Typical AC Signal Delay (Off) | 29 (+/- 8) milliseconds |
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| Required External Power | None |
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| I/O Connection Hardware | 1771-RTP1 |
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| Wiring Arm | 1771-WN |
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| Backplane Current | 0.65 Amps |
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| Module Update Period | 100 Microseconds |
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| Slots | 1 Slot |
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| Outputs | 8 Digital Outputs |
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| Max Input Frequency | 1 Megahertz (in counter mode) |
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| Inputs | 12 Digital Inputs (3 Per Counter) |
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| Module Type | High-Speed Counter Module |
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TECHNICAL INFORMATION
Features
- Provides four independent counting channels with multiple software operating modes.
- Accepts differential and single-ended field input wiring configurations.
- Supports counting rates up to 1 MHz for high-frequency signal monitoring.
- Delivers a fast internal update period of 100 microseconds.
- Includes eight isolated digital outputs arranged into two separate groups.
- Features a wide programmable counter range from 0 to 999,999.
- Transfers counter registers to PLC-5 processors using Block Transfer Read and Write commands.
TECHNICAL INFORMATION
Applications
- High-speed item counting on industrial packaging and assembly lines.
- Shaft position and velocity feedback using incremental optical encoders.
- Flow totalizing interfaced to pulse-output flow metering devices.
- Frequency monitoring and production rate measurement in process automation.
TECHNICAL INFORMATION
Connections / Interfaces
- Terminates external field wiring through the removable 1771-WN wiring arm.
- Supports optional connection through the 1771-RTP1 remote termination panel hardware.
- Accepts Belden 9182 shielded twisted-pair cable or Category 2 equivalent wiring.
- Maintains field wiring runs up to a maximum distance of 250 feet (76.2 meters).
TECHNICAL INFORMATION
Installation Guidelines
- Installs into any available single I/O slot in a 1771 chassis.
- Set backplane keying plastic tabs between pins 24-26 or 28-30.
- Verify that the chassis backplane power supply can deliver 650 mA.
- Ensure ambient chassis enclosure operating temperatures remain between 32 and 140 degrees Fahrenheit.
TECHNICAL INFORMATION
Configuration Guidelines
- Select input voltage thresholds and hardware counter modes using onboard switches.
- Configure encoder modes for X1 or X4 quadrature evaluation.
- Use Block Transfer Write (BTW) instructions to configure channel modes and presets.
- Use Block Transfer Read (BTR) instructions to import count registers and diagnostic status.
TECHNICAL INFORMATION
Compatibility
- Operates in all standard Allen-Bradley 1771 I/O chassis architectures.
- Communicates with Allen-Bradley PLC-5 programmable logic controller systems.
- Directly interfaces with Allen-Bradley Bulletin 845H, 845P, 845L, 845E, and 845K encoders.
- Accepts pulse inputs from standard mechanical limit switches and proximity sensors.
TECHNICAL RESOURCES
Documentation
COMPATIBILITY
Compatibility & Replacement
COMPATIBLE MODELSOperates in all standard Allen-Bradley 1771 I/O chassis architectures. Communicates with Allen-Bradley PLC-5 programmable logic controller systems. Directly interfaces with Allen-Bradley Bulletin 845H, 845P, 845L, 845E, and 845K encoders. Accepts pulse inputs from standard mechanical limit switches and proximity sensors.
Verify compatibility against the exact Part Number, revision and manufacturer documentation before ordering.
PART VERIFICATION
Before You Order
Industrial automation parts can share similar model names, suffixes and revisions. Confirm the complete manufacturer Part Number before purchase.
01Check Part NumberMatch the complete ordering code on the existing unit.
02Confirm RevisionCheck suffix, hardware or firmware when applicable.
03Send a Label PhotoWe can review a clear label photo when identification is uncertain.
ORDERING PROCESS
From RFQ to Dispatch
1Submit Part Number2Verify Product Identity3Confirm Stock & Condition4Issue Quotation5Dispatch & Tracking
PRODUCT FAQ
Frequently Asked Questions
What is the primary function of the Allen-Bradley 1771-VHSC module?
The 1771-VHSC counts high-speed pulses from encoders, proximity switches, and flowmeters for PLC-5 systems.
What maximum input frequencies are supported by the 1771-VHSC?
The module supports up to 1 MHz in counter mode and 250 kHz in quadrature encoder mode.
Which field wiring arm is required for the 1771-VHSC module?
The module requires a catalog number 1771-WN field wiring arm for all field connections.
What is the reference price for a replacement 1771-VHSC module?
Observed market reference pricing is around $235.00 for used or refurbished units. These figures represent indicative market reference pricing only and are not a final quotation.
